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THE ESSENTIAL MAGAZINE OF ASTRONOMY ISSUE 83 Raise your astro imaging to a new level with our expert tips p.74 Deep Sky treats for backyard observers p.68 Mars explorers train in the Australian Outback p.18 HIDDEN OCEANS: Are moons where we should look for life? p.90 A winning ensemble from Celestron p.86 Big Hurdles for Big Scopes p.24 TEST REPORT:

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Page 1: Australian Sky & Telescope -2015

THE ESSENTIAL MAGAZINE OF ASTRONOMY

ISSUE 83

Raise your astro imaging to a new level with our expert tips p.74

Deep Sky treats for backyard observers p.68

Mars explorers train in the Australian Outback p.18

HIDDEN OCEANS: Are moons where we should look for life? p.90

A winning ensemble from Celestron p.86

BigHurdles for Big Scopesp.24

TEST REPORT:

Page 2: Australian Sky & Telescope -2015

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Page 3: Australian Sky & Telescope -2015

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Page 4: Australian Sky & Telescope -2015

4 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

8 Spectrum A Year of Discovery By Jonathan Nally

10 News Notes• Cometskimspastmars• Evidenceforlunarvolcanism• Workbeginsongiantscope andmore…

13 10 & 5 Years Ago By Jonathan Nally

14 Countdown to Pluto By Jonathan Nally

16 Discoveries Cometcompatriots By David Ellyard

17 No Landing Here NASA'snewviewofEuropa

February/March 2015 Vol. 11, No. 2

ContentsNEWS & FEATURES

Cover Story

AS&T TEST REPORT

86 A Lot for a Little AnensembleofCelestronequipment providesexcellentvisualand photographicperformance. By Rod Mollise

OBSERVING & EXPLORING

24 Flawed Giants Theworld’slargestopticaltelescopeshavehadtoovercomeserioushurdles,delayingtheirscientificsuccess. By Jonathan Fortney

18 Outback Mars TheAustraliandesertistheidealplacetosimulatelivingonMars. By Jonathan Clarke

36 Hubble Goes the Distance Usingnature’sgravitationallenses,astronomersarepushingtheSpaceTelescopetoitsverylimits. By Govert Schilling

50 Binocular Highlight TheAlphaPerseiAssociation By Gary Seronik

52 Tonight’s Sky StalkingtheHunter By Fred Schaaf

54 Sun, Moon, and Planets Dynamicduo By Jonathan Nally

58 Celestial Calendar LastchanceforCometLovejoy By David Seargent

59 Celestial Calendar BLOrionis By Alan Plummer

60 Double Star Notes ProwlingthroughPuppis By Ross Gould

p.36 Hubble's deepest views

p.24 Technical challenges of giant scopes

44 Into Thin Air Astronomers’continualquestfor optimalseeingconditionshasensured thatleadingobservatoriesgetbuilton ever-highermountaintops. By Tom Gale

84 Open Skies SydneyObservatory'snewdomeandtelescopeofferaccessforall. By Toner Stevenson

84 A Universe of Dark Oceans TheicybodiesoftheouterSolarSystemmightbeteemingwithlife. By Caleb Scharf

Page 5: Australian Sky & Telescope -2015

www.skyandtelescope.com.au 5

73 Telescope Workshop Awesome Binocular Telescope By Gary Seronik

74 Composing the Universe Planning your composition can raise your imaging to a whole new level.

By Robert Gendler

65 Subscription Offer Subscribe and receive a 2015

Astronomy Calendar or Yearbook!

AUSTRALIAN SKY & TELESCOPE (ISSN 1832-0457) is published 8 times per year by Odysseus Publishing Pty Limited, PO Box 81, St Leonards, NSW, 1590. Phone (02) 9439 1955, fax (02) 9439 1977. © 2015 Odysseus Publishing Pty Limited. All rights reserved.

ON THE COVER: Like its bigscope brethren, the Gran Telescopio Canarias has had to overcome some big obstacles. PABLO BONET / IAC

THE ASTRONOMY SCENE

SUBSCRIBE TO AS&T

90 Gallery Best photos from our readers

94 Marketplace

97 Index to Advertisers

97 Manufacturer and Dealer Directory

98 Focal Point Stu's Last Lesson By Damian G. Allis

p.18 Training for Mars in the Aussie desert

p.84 Sydney's historic observatory

p.74 Take better astrophotos

64 Targets The Fire Down Below By Sue French

66 Exploring the Solar System An Observational Mystery By Thomas A. Dobbins

68 Deep Sky Marvels Hopping Around the Backyard Sky By Rod Mollise

Page 6: Australian Sky & Telescope -2015

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Page 8: Australian Sky & Telescope -2015

8 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Jonathan NallySpectrum

EDITORIALEDITOR Jonathan Nally

DESIGN Simone MarinkovicCONTRIBUTING EDITORS

John Drummond, David Ellyard,Ross Gould, Steve Kerr,

Alan Plummer, David SeargentEMAIL [email protected]

ADVERTISINGADVERTISING MANAGER Jonathan NallyEMAIL [email protected]

SUBSCRIPTION SERVICESTEL 02 9439 1955

EMAIL [email protected]

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Printed by Webstar

Australia distribution by Network Services. New Zealand distribution by Gordon & Gotch. © 2015 F+W Media, Inc. and Odysseus Publishing Pty Limited. No part of this publication may be reproduced, translated, or converted into a machine-readable form or language without the written consent of the publisher. Australian Sky & Telescope is published by Odysseus Publishing Pty Limited under licence from F+W Media, Inc. as the Australian edition of Sky & Telescope. Australian Sky & Telescope is a registered trademark of F+W Media, Inc. USA. Articles express the opinions of the authors and are not necessarily those of the Editor or Odysseus Publishing Pty Limited. ISSN 1832-0457

THE ESSENTIAL MAGAZINE OF ASTRONOMY

ISSUE NO 83FEBRUARY/MARCH 2015

SKY & TELESCOPE INTERNATIONAL

EDITOR IN CHIEFPeter Tyson

EDITORIALSENIOR EDITOR

Alan M. MacRobert EQUIPMENT EDITOR Sean Walker

SCIENCE EDITOR Camille M. CarlisleWEB EDITOR Monica Young

OBSERVING EDITOR Susan N. Johnson-Roehr

SENIOR CONTRIBUTING EDITORS J. Kelly Beatty, Robert Naeye, Roger W.

Sinnott DESIGN DIRECTOR Patricia Gillis-Coppola

ILLUSTRATION DIRECTOR Gregg Dinderman

Founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer

A Year of Discovery

Australian Sky & Telescope is now on Facebook. Complementing our website, Facebook helps keep you alerted to astronomy news and information about Australian Sky & Telescope. Visit www.skyandtelescope.com.au, click on the Facebook link, and become a fan today.

It's great to back in the editor's hot seat at Australian Sky & Telescope, 10 years a� er we launched the magazine. So much has changed during that decade, but one thing has stayed the same — the � ood of amazing discoveries and insights

into our cosmos just keeps getting stronger as each year goes by. New telescope technologies and huge computing power are enabling astronomers to tackle research problems they could only have dreamed about in decades past. We’re truly experiencing a golden age discovery.

For all that new technology, though, there are always challenges to solve. As our cover story illustrates, as telescopes grow in size and complexity, so too does the potential for things to go wrong. Today’s telescopes are huge enough, but tomorrow’s behemoths — such as the recently approved � irty Metre Telescope, and the Square Kilometre Array — will no doubt present di� culties that haven’t been anticipated yet. But the engineers and scientists who conceive, design and build these giants are a resourceful lot, and will no doubt rise to the occasion.

� is is going to be such an exciting year for space exploration, with the New Horizons spacecra� soon to reach Pluto, and Dawn continuing its reconnaissance of the asteroid belt as it arrives at Ceres. Two missions, two dwarf planets. We’ll also be following the life and times of Rosetta with great interest, as it heads sunward in the company of comet 67P/Churyumov-Gerasimenko.

Back down here on Earth, and kudos to Sydney Observatory for commissioning a new telescope that will be accessible to those with physical disabilities. Equipped with a special eyepiece, the viewer will be able stay in one spot as the telescope moves to track di� erent targets. � e building’s dome is actually that from the old astrograph building that was demolished in 1986, and the astrograph itself will return to be put on display. I have fond memories of using this instrument to take photographic plates of Comet Halley as part of the International Halley Watch project. It was a great old device, and it's wonderful to know that it’ll be there to show the younger generations what a 'real' telescope looked like.

I'm keen to hear your ideas for how we can make AS&T even better for you. Please drop me a line at [email protected] and let me know what you'd like to see more of in the magazine.

Jonathan Nally

Editor

[email protected]

Page 9: Australian Sky & Telescope -2015

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Capturing impressive deep-sky astroimages is easier than ever with Celestron’s new Rowe-Ackermann Schmidt Astrograph, the perfect companion to today’s top DSLR or astronomical CCD cameras. This fast, wide-field f/2.2 system offers two huge advantages over traditional f/10 astroimaging: better apparent tracking and shorter exposures. That means you’ll create better-looking astroimages in a fraction of the time, even without the use of an autoguider.

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ROWE-ACKERMANN SCHMIDT ASTROGRAPHCGE PRO MOUNT

Page 10: Australian Sky & Telescope -2015

News Notes

Comet Siding Spring Skims MarsSOLAR SYSTEM I

History was made on October 19, 2014, as a comet passed closer to a planet (without hitting it)

than ever before in recorded memory. Unfortunately for backyard observers, that planet was Mars.

Comet Siding Spring (C/2013 A1) passed 137,000 kilometres above the Red Planet’s surface — about a third of the distance between the Earth and the Moon. The dust tail left in its wake missed Mars, but not by much.

This Oort Cloud comet is a first-time visitor to the inner Solar System. When spotted in January 2013 by veteran comet-hunter Rob McNaught,

C/2013 A1 was still 7.2 astronomical units (1.1 billion km) from the Sun. By then its nucleus had already started releasing gas and dust to form a coma. Most comets don’t ‘turn on’ until they get much closer in.

Planetary scientists, excited by the prospect of studying a pristine relic from the Solar System’s formation, readied an armada of spacecraft and ground-based telescopes for the event. The most anticipated observations came from NASA’s three orbiters: Mars Reconnaissance Orbiter, Mars Odyssey, and the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft.

Also on the scene were the European orbiter Mars Express and India’s Mars Orbiter Mission (MOM), as well as the Opportunity and Curiosity rovers on the planet’s surface.

As a precaution, engineers from NASA and the European Space Agency manipulated the trajectories of their respective orbiters to put the spacecraft all on the opposite side of the planet during the window of greatest danger. Initial results confirm these craft weathered the event unharmed by debris.

Comet Siding Spring passed through its orbit’s perihelion just 5½ days after zipping past Mars, so activity was expected to be very high during its pass. However, observers noted a fall-off in the comet’s brightness as the encounter neared. Preliminary images from MRO’s HiRISE camera also suggest that the comet’s icy nucleus is only half as large as the 700 metres scientists had estimated.

Meanwhile, MAVEN and MOM were both watching for changes in the composition and temperature of the planet’s upper atmosphere as the comet’s extended gas-and-dust coma briefly enveloped the planet. Scientists are working to disentangle the effects from the coronal mass ejection that passed Mars around the same time.

J. KELLY BEATTY

IN BRIEF

10 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Citizen Scientists Probe Early Galaxies. Data collected by Galaxy Zoo volunteers show galaxies form barred structures much earlier in cosmic history than previously thought. Previous observations have shown that the fraction of barred galaxies dropped from 50–70% in the nearby universe to 10% when the universe was only 6 billion years old. But as Brooke Simmons (Oxford, U.K.) and colleagues report in an upcoming Monthly Notices of the Royal Astronomical Society, extending the data back to when the universe was only 3 billion years old shows that the number of barred galaxies was still as high as 10%, and not the expected zero. These early galaxies might have formed either because their contents settled down earlier than thought would happen, or because they were formed by two galaxies colliding.

SHANNON HALL

Neutrino Detection Confirms Sun’s Power Source. Deep inside the Sun pairs of protons fuse to form deuterium nuclei, kick-starting nuclear fusion. Although the complex ‘proton-proton’ chain is now standard theory, the solar neutrinos produced in the chain’s first step have eluded detection for decades. Now, researchers using the Borexino detector — a tub of liquid designed to emit light when neutrinos interact with the liquid’s electrons — have captured the elusive neutrinos. The results, published in the August 28 issue of Nature, confirm that 99% of the Sun’s power comes from the proton-proton fusion process and demonstrate the intricate interplay between theory and observation. Although the particles’ existence was not in question, it’s an incredible feat to detect them.

SHANNON HALL

Comet Siding Spring (below center) made its closest approach to Mars (big reddish blob) on October 19th, a few hours after astrophotographer Damian Peach captured this image of the pair. SEN / DAMIAN PEACH

Page 11: Australian Sky & Telescope -2015

www.skyandtelescope.com.au 11

Images from NASA’s Lunar Reconnaissance Orbiter show 70 small, curious features that might be from volcanic eruptions in the past 50 to 100 million years, Sarah Braden (Arizona State University) and colleagues report October 12th in Nature Geoscience.

The suspect locations are what geologists term irregular mare patches, or IMPs. These distinctive rock deposits, up to 5 kilometres long, can be either rough, blocky outcrops or smooth patches with uniform texture. Both types exhibit very few impact craters, even down to the 0.5-metre resolution of the narrow-angle camera on NASA’s Lunar Reconnaissance Orbiter. The lack of craters suggests that the features are relatively young.

The best known IMP, named Ina (or Ina D), was spotted in images taken by the crew of Apollo 15 in 1971. Even back then, lunar geologists had a hunch that Ina was a collapsed vent topping a low, broad, shield volcano. But Ina’s age has been uncertain.

Now, thanks to LRO’s keen resolution, that site and many others appear to be quite young. The

IMPs’ spectral characteristics suggest relatively fresh surfaces that have not been darkened by eons of exposure to space radiation. The smooth deposits are also the same thickness as other lunar basalt flows and haven’t had their steep edges worn down, as older features have. Curiously, all the IMPs are on the Moon’s nearside hemisphere, although statistically a few should have been spotted on the farside.

So, rather than a complete shutdown of lunar volcanism at least a billion years ago, as had been widely assumed,

Work Begins on Thirty Metre Telescope. Officials gathered on October 7 for the dedication and groundbreaking of the Thirty Metre Telescope (TMT), slated for completion in 2022. TMT will combine 492 individual hexagonal reflectors, each 1.4 metres across, in a honeycomb primary mirror with an effective diameter of 30 metres. The primary promises to provide 144 times more collecting area and 10 times better spatial resolution than the Hubble Space Telescope. Ceremonies were interrupted for several hours by a peaceful protest from native Hawaiians who oppose additional telescopes on the sacred summit of Mauna Kea. (See page 24 for more on hurdles faced by big scopes.) J. KELLY BEATTY

Gamma-ray Novae Explained? Astronomers might have an explanation for why classical novae emit gamma rays. Laura Chomiuk (Michigan State

University) and colleagues used several radio arrays to observe the nova V959 Monocerotis, starting about two weeks after the gamma-ray discovery and spread over several months. The observations revealed synchrotron radiation, which is produced by relativistic particles and suggests the presence of shock fronts. What probably happened is, when the white dwarf went nova, it first spewed out thick, warm gas in a spherical shell around itself and its companion. As the gas flowed past the other star, the interaction forced the gas into a dense belt instead of a sphere. When the white dwarf later blew out a fast wind, the thick stuff funneled that wind out along the poles. Shocks formed at the boundaries between the slower, thick outflow and the faster, thin outflow. These shocks accelerated the particles responsible for the gamma rays and the synchrotron emission, the team reports October 8 in Nature. CAMILLE M. CARLISLE

Small Galaxy Boasts Big Black Hole. Astronomers have detected a supermassive black hole in the center of the ultracompact dwarf galaxy M60-UCD1 — where it has no right to be. Ultracompact dwarf galaxies are similar in size to globular clusters but at least 10 times more massive. Scientists have debated whether they are unusually massive star clusters or the remnants of larger galaxies that have been stripped down to their cores. But dwarf galaxies normally don’t have supermassive black holes, and M60-UCD1’s black hole is 21 million times the mass of the Sun, about 5 times more massive than the Milky Way’s black hole. The mass suggests the original galaxy had a central bulge roughly 100 times more massive than M60-UCD1’s total stellar mass, Anil Seth (University of Utah) and colleagues report September 18 in Nature. The detection is the first observational evidence for the stripped-down theory. EMILY CONOVER

LUNAR I Geologically Recent Volcanism on the Moon

the process was apparently much more drawn out. Pockets of molten rock must have remained in the lunar mantle until very recently — and might still be there now. These findings have implications for how warm the lunar interior still is (and the true extent of its partially molten core). They also might suggest that heat flow measurements taken during the Apollo 15 and 17 missions were not anomalously high after all, as many have thought.

J. KELLY BEATTY

Shown in this oblique view from NASA’s Lunar Reconnaissance Orbiter, the feature Ina (big mottled region) might be from a recent volcanic eruption on the Moon. The shallow depression is about 50 metres deep. Illumination is from the bottom; the smooth patches are convex and lie above the rough surface. (If the smooth patches look like holes to you, imagine pressing your thumb into Ina’s depression — it can help reset your perspective of the edges.) NASA

/ GSFC / ARIZONA STATE

UNIVERSITY

IN BRIEF

Page 12: Australian Sky & Telescope -2015

12 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

News Notes

GALACTIC CENTER I G2 Survives Pass Last year, the world’s astronomers watched a mysterious, gaseous object called G2 slingshot around the supermassive black hole at the centre of the Milky Way. Astronomers first spotted G2 in 2011, and its crazy orbit immediately sparked debate: G2 makes a beeline for the black hole, whips around it, and shoots straight back out again. To do so, the object must have somehow lost enough angular momentum that, instead of following a more circular orbit, it started to fall headlong toward the black hole, called Sagittarius A* (pronounced "A star").

The answer to the mystery is twisted up in G2’s nature: is it merely a gas cloud, or does it hide a star inside?

The hope was that G2 would reveal its nature during its close encounter with Sgr A* in March 2014. However, the data are still inconclusive. The issue is that the two teams

that spearheaded the infrared observations of our galactic downtown depend on different types of data.

The Max Planck Institute team has fabulous measurements from the SINFONI spectrograph at Paranal Observatory in Chile. These data show an extended gas tail disrupted during the close pass. On the other hand, the UCLA team has exquisite images from the Keck Observatory on Mauna Kea. The images for autumn and winter 2014 show an unresolved compact object that didn’t brighten and stuck to its orbit during the pass, as you’d expect for a dust-enshrouded star.

The discrepancy might exist because the two types of observations are looking at different features: the spectra catch gas that’s stretched out from the orbit, while the images catch the dusty shell heated by

the star within. The MPI observations thus wouldn’t rule out a star; they would just show that gas was yanked out during the close pass.

As G2 moves farther from Sgr A*, the view will become clearer. And if Sgr A* slowly brightens in the next few years, it’ll indicate that it did indeed tear gas off G2 and that this gas fell through the accretion flow toward the black hole. That could reveal G2’s nature and how much stuff it lost during the pass.

A completely different probe is also in place: the star S2, which at closest approach whizzes closer to the black hole than G2 did. S2 will reach pericentre around 2018, and the effect it has (or doesn’t have) on the hot gas surrounding the black hole could reveal much about the environment and, potentially, why G2 behaved the way it did during its pass.

CAMILLE M. CARLISLE

Two studies suggest that some of the ultraluminous X-ray sources (ULXs) thought to be beefy black holes are created by much less massive objects.

ULXs spew out X-rays at luminosities roughly a trillion times the Sun’s X-ray luminosity. The standard explanation for a ULX is that the X-rays come from extremely hot material that a black hole has pulled from a companion star. The more massive the black hole, the brighter its accretion disk can be.

But ULXs are uncomfortably bright: to explain them, a stellar-mass black hole would need to reach or surpass its maximum gas-gobbling rate, called the Eddington limit. That might be possible due to ‘force-feeding’ that can occur under certain conditions. Or these sources might be intermediate-mass black holes (IMBHs), theoretical objects with masses of hundreds to thousands of Suns that would fill the no-man’s land between stellar-mass and supermassive black holes.

Among ULXs, the sources M82 X-1 and ESO 243-49 HLX-1 are the two best IMBH candidates; evidence suggesting that M82 X-1 is a 400 solar-mass black hole appeared in the September 4, 2014, issue of Nature.

Now, a pair of papers published on October 9 in Nature demonstrate that two other ULXs are not IMBHs.

Christian Motch (University of Strasbourg, France) and colleagues observed variations in a ULX’s emission in the spiral galaxy NGC 7793. The measurements pegged the orbital period of the black hole and its companion to 64 days and constrained the black hole’s mass to be less than 15 solar masses. This means that the black hole gobbles up matter at twice its Eddington limit, confirming the force-feeding picture.

The more surprising result comes from Matteo Bachetti (University of Toulouse, France) and colleagues, who detected pulsations from another ULX in the galaxy M82, proving it’s not a black hole at all, but a pulsar. Astronomers hadn’t expected pulsars to be ULXs, because to do so pulsars would have to exceed their Eddington limits to an extreme degree. In this case, the pulsar surpasses its Eddington limit by a factor of 100 — an unprecedented amount, and difficult to reconcile with theory.

EMILY CONOVER

BLACK HOLES INo Big Beast for Two ULXs

GALAXIES I Mergers Create Disk Galaxies

Observations from several radio telescopes confirm that, when two galaxies merge, their progeny often have extended gaseous disks.

Simulations from the 1970s suggested that, when two big disk-shaped galaxies merged, they’d create a big elliptical galaxy, a fairly featureless spheroid of stars. But about a decade ago, better simulations by several teams showed that, if the disk galaxies have a lot of gas, the object their merger creates will also be a disk galaxy, with spiral arms or maybe even a central bar.

Junko Ueda (National Astronomical Observatory of Japan) and colleagues have now confirmed this prediction with observations, published in the September Astrophysical Journal Supplement. The team looked at emission from cold molecular gas from 37 merger-created galaxies, using both new and archival data. Of the 37 galaxies, the team easily detected gas in 30, and 24 showed signs of disk rotation.

Of the 24, 11 (46%) have big gas disks, meaning they are on their way to forming either spiral or lenticular galaxies. The disks of the remaining 13 are smaller than their stellar bulges; those galaxies will become ellipticals.

CAMILLE M. CARLISLE

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Uranus Kicks Up A StormMany astronomy enthusiasts had a hard time getting excited about Uranus a� er Voyager 2's 1986 � yby. Unenhanced imags of the planet showed a featureless aquamarine ball — in stark contrast to Jupiter's and Saturn's richly detailed belts and storms. But recent near-infrared images from the 10-metre Keck II telescope in Hawaii demonstrate that � rst impressions can be deceiving.

� e images, taken in 2003 and 2004 with adaptive optics to counter atmospheric blurring, revealed dozens of discrete clouds, more than the total seen in all previous observations up to 2000. � e clouds vary in size, brightness and longevity, proving that Uranus (like Neptune) has a dynamic and complex atmosphere a� er all… � e major reason for Uranus' new-found dynamism is probably its extreme seasonal cycle. Uranus is the Solar System's only planet whose rotation axis is tipped nearly into its orbital plane.

Ten years later, and Uranus is still kicking up storms. In November 2014, astronomers using Keck II were tracking a huge storm and several smaller ones. Even amateur astronomers with advanced gear could see them.

Finding the First GalaxiesIn May 2009, astronauts installed two new cameras in the Hubble Space Telescope, making Hubble more powerful than ever. � e new Wide-Field Camera 3 (WFC3) increases Hubble’s sensitivity and � eld of view at near-infrared wavelengths, improving its ability to search for distant galaxies by as much as a factor of 20.

It didn’t take long for WFC3 to make its mark. Garth Illingworth, Rychard Bouwens (both at the University

of California, Santa Cruz), and their colleagues recently used WFC3 to � nd 5 galaxies, circled in the image to the le� , that are more distant than any seen before, pushing our knowledge of galaxy evolution back to just 600 million years a� er the Big Bang (a redshi� of about 8.5).

� ese early galaxies are about the same distance as gamma-ray burst 090423, which recently established the record for most-distant known object (AS&T: October 2009, page 34). But we’re interested in more than just breaking records. We want to understand how galaxies formed, and how they built themselves up into the giant congregations that we see today.

As covered in this issue (pages 36-42), astronomers are now using the serendipitous alignment of galaxy clusters to act as ‘zoom lenses’ and push back the time and distance to which Hubble can see into the distant past. Astronomers hope to see almost back to the dawn of time.

February 2005

Feb/Mar 2010

10 & 5 Years AgoAstro Calendar

WA AstrofestMarch 28Biennial Victorian astronomy conference, hosted in 2015 by the Bendigo Astronomical Societycaastro.org/Astrofest

VASTROCApril 17-19Biennial Victorian astronomy conference, hosted in 2015 by the Bendigo Astronomical Societyvastroc.net

Royal Astronomical Society of NZ ConferenceMay 8-10Annual meeting of New Zealand's astronomersrasnz.org.nz/Conference/

Trans-Tasman Symposium on OccultationsMay 11Australasian get-together for occultation observers, this year to be held in Lake Tekapo, NZoccultations.org.nz

South Paci� c Star PartyMay 14-17Annual star party hosted by the Astronomical Society of NSWasnsw.com/spsp

CWAS AstrofestJuly 18-19Annual conference held in Parkes (home of 'the Dish'), including the David Malin Awardscwas.org.au/Astrofest/

Queensland AstrofestAugust 7-16Annual star partyqldastrofest.org.au

National Science WeekAugust 15-23Lots of public astronomy activities held around Australiascienceweek.net

WHAT’S GOING ON? Do you have an event or activity coming up? Email us at [email protected].

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14 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Countdown to Pluto Jonathan Nally

As I write this, NASA's New Horizons spacecraft has just come out of its final period of

hibernation. On December 7, 2014, a simple "I'm awake and okay" tone was received at the agency's Deep Space Network station at Tidbinbilla, near Canberra. That tone was carried by radio waves more than 4.6 billion kilometres from the spacecraft to Earth, taking a little under four and a half hours to reach us.

Now that the craft is conscious again and preparing for its final run in to Pluto in July this year, the serious investigations can begin in earnest. Let's look at the timeline between now and encounter day.

In the middle of January the ‘science phase’ began, as New Horizons started to collect data on Pluto and its moons. They're still small dots in the distance as this stage, but they'll grow bigger each day as the spacecraft closes in at a speed

of about 50,000 kilometres per hour.Three months out, and still

100 million kilometres away, the spacecraft's cameras will be able to start making their first maps of Pluto's surface. By ten weeks out, New Horizons will begin to provide better views than the Hubble Space Telescope has given us so far. And in the last few weeks before encounter, scientists will map surface maps every half-day to look for daily changes.

On encounter day, July 14, 2015, detailed observations at many wavelengths will be made of the dwarf planet's surface and atmosphere, and the same goes for its largest moon, Charon. Details as small as 25 metres across should be seen.

New Horizons' closest approach to Pluto will be at a distance of about 10,000 kilometres and at a speed of 14 kilometres per second. Closest approach to Charon will be about 27,000 kilometres.

Ready For A Close EncounterNew Horizons awakens and prepares for Pluto

At this time, Pluto will be approximately 4.92 billion kilometres from Earth, and it will take 4 hours and 25 minutes for New Horizons' signals to reach us.

But the science won't stop on encounter day. After passing by, New Horizons will turn around and look back to make more observations — it'll be looking to see if there's any haze in Pluto's atmosphere, and whether there are any rings circling the planet. Rings are often easiest to see when backlit by sunlight.

It'll take up to nine months for the entire encounter data set to be downloaded back to Earth. Meanwhile, as reported in our January issue, New Horizons will be retargeted onto an interception course with a Kuiper Belt object — one of Pluto's icy cousins in the far reaches of the Solar System.

I can't wait for our first up-close look at Pluto. The next six months are going to be absolutely thrilling. ✦

New Horizons' trajectory through the Solar System to Pluto and beyond to its Kuiper Belt target, PT1. Also shown as many are the positions of the millions of smaller bodies that inhabit our neighbourhood. ALEX PARKER

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David EllyardDiscoveries

David Ellyard presented SkyWatch on ABC TV in the 1980s. His StarWatch StarWheel has sold over 100,000 copies.

Edmond Halley, who flourished around the start of the 18th century, had many remarkable achievements. Among

them was the first detailed study of the ‘variation of the compass’ (the difference between true north and magnetic north) up and down the Atlantic Ocean, undertaken to find a method of measuring longitude; his proposal that we could use the transits of Venus to determine the distance between the Earth and the Sun; and his encouragement of Isaac Newton to prepare for publication his epoch-making book the Principia, which Halley also paid for.

But for most people Halley’s name is associated principally with ‘his’ comet. Halley’s is the best-known of the comets, uniquely combining brightness (bright enough at times to be seen in the daytime) with regular and not too infrequent appearances (every 76 years or so). So it is worth remembering that this month celebrates (on 30 March) the first recorded closest approach (‘perihelion passage’) of that comet to the Sun, as observed by Chinese

astronomers in 239 BCE. That and many other sightings confirm

that the comet was well-known long before Halley took an interest. His name became attached (after his death) because he deduced that the comet was a regular visitor, and that previous appearances in 1531, 1607 and 1682 were of the same comet. He predicted that it would come by again in 1759, and it did. His immortality was assured. We might also note that in order to calculate the orbit of the comet at its various appearances (and to show they all were the same) he relied on methods Newton had set out in the Principia. So Halley got his reward for supporting and sponsoring Newton.

On another March date, a century before Halley, the Danish astronomer Tycho Brahe found a new comet in the constellation Pisces. That discovery, on 5 March 1590, allows us to draw the great Tycho into the story. Like Halley he was a man of many achievements: Court Astronomer to the Kings of Denmark and Bohemia; source of the most accurate data on the positions of the

Comet compatriots

heavenly bodies in the pre-telescope age; creator of a model of the Solar System that challenge both Ptolemy and Copernicus; and first observer of ‘Tycho’s Star’, the great supernova of 1572 (which may have been the star referred to in Hamlet by Shakespeare). Tycho also wore a false nose, the original having (reputedly) been sliced off by a rival in a duel over mathematics.

Tycho had been the most illustrious observer of the Great Comet of 1577, though many other people saw it too, including in the Middle East. Tycho made many measurements of the position of the comet, data later used by his assistant and successor Johannes Kepler to help determine his ‘laws’ of planetary motion.

Tycho’s crucial discovery concerned how far away the comet was. The great Aristotle, whose ideas were still influential nearly 2,000 years after his time, believed comets were just disturbances in our own atmosphere. Tycho put that idea to flight by comparing the position of the comet against the background stars, when compared with that of the Moon, and as observed simultaneously from Copenhagen and Prague (where he had a correspondent). The position of the Moon was different when observed from the two locations, but that of the comet was not, indicating to Tycho that the comet was further away than the Moon (and therefore far beyond our atmosphere).

This information had profound implications. It not only rubbished Aristotle’s ideas about comets, but also put the fleeting appearances of the comet far out in the realm beyond the Moon where supposedly nothing ever changed. Furthermore, to move as observed in that realm, the comet would have to pass right through the ‘crystalline spheres’ which (again according to Aristotle and Ptolemy) carried the heavenly bodies in their orbits around the stationary Earth. All of this nibbled away at the traditional view of the cosmos, now sanctioned by the Church, which later gave Galileo such a hard time over the matter.

It was Halley who finally put comets in their place, arguing that they were just small members of the Solar System, orbiting the Sun and following the rules uncovered by Newton and Kepler. That is not to demean their importance. Current studies suggest that they may have been the source of both water and biologically-important molecules for the infant Earth, with which they frequently collided. But that is another story. ✦

Comet 1P/Halley was named after Edmond Halley, but not discovered by him. Halley was the first to work out that some comets returned again and again to the inner Solar System. ESO

Halley, Tycho and comets

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Cosmic Views

NO LANDING ZONEJupiter's icy moon Europa is seen in brilliant

detail in this newly reprocessed picture made from images taken by the Galileo spacecraft in

the 1990s. Europa featured in Arthur C. Clarke's 2010: Odyssey Two (the sequel to 2001: A Space Odyssey), in which a message was sent to Earth:

"All these worlds are yours except Europa‥ attempt no landing there". As the late Clarke

was right about so many other things, perhaps we should take this warning seriously.

NASA/JPL-CALTECH/SETI INSTITUTE

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Outback Mars

Two spacesuited figures walk across a rocky plain surrounded by steep hills in the orange light

of the late afternoon. Trundling behind them is an eight-wheeled robot. Overhead a small quadcopter streams video back to a field operations centre in a nearby vehicle, from where the robot and astronaut operations are being co-ordinated.

This is not a scene from a science fiction movie, or even a NASA conceptualisation of future interplanetary explorers. Instead, it was a trial carried out during the Mars Society Australia’s Mars Robot Challenge Expedition near Arkaroola, 700 kilometres north of Adelaide in South Australia's Flinders Ranges.

The July 2014 expedition comprised 30 people, a mixture of engineering and geological researchers, science and engineering graduate and

Outback MarsThe Australian desert is the ideal place to simulate living on Mars

undergraduate students from Australia and India, plus volunteers, accompanied by seven walking, driving and flying robots. Supporting them was a network of people in Mumbai, Melbourne, Sydney, Canberra, Adelaide and the US.

Many expeditioners mean many goals. The robotics teams wanted to test their robots in terrains that approximated what you might find on the Moon and Mars. Operational researchers planned to evaluate interactions between astronauts, rovers and mission control. Astrobiologists wanted to look for signs of life in ancient rocks. Field geologists hoped to evaluate the effectiveness of the robots and astronauts in collecting data. And the expedition co-ordinator hoped to herd all these cats safely and happily through the two weeks of the expedition.

Testing Robots in The FieldMost activities centred around the capabilities of the robots. Many people often have quite unrealistic expectations of robots — they imagine autonomous, perhaps even self-aware, droids like those of Star Wars. The reality is quite different — Star Wars droids are a long way off. Autonomous robots that can roam around planetary surfaces are extremely difficult to achieve, have limited capabilities and are very slow.

Most importantly for researchers like those on the expedition, they are very expensive to develop and difficult to test within limited time frames.

So we focussed on human-centred robots. These are machines that are either directly or remotely controlled, and support human activities. Such robots are not only easier to build and

JONATHAN CLARKE

A view of a Martian Valley, taken by NASA's Curiosity rover.NASA/JPL-CALTECH/MSSS

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test than autonomous machines but are potentially far more powerful. � e most sophisticated and capable space robots to date include those on the International Space Station, such as the robot arms. It is in their capacity to enhance human capabilities that robots show their greatest potential in space exploration.

But why test them in the � eld? Because � eld environments are far more diverse and less controlled than a laboratory — robots that work well in the lab may not work in the � eld, and extensive � eld trials are needed not only to ensure reliability but to con� rm the best designs. � is is true whether you are designing robots for use on Earth of for even more demanding applications in space.

� rough the � eld-testing at Arkaroola, ideas for the next generation of robots to be deployed throughout the Solar System are being shaped. Even more importantly, the next generation of engineers are gaining experience in the messy world beyond the laboratory.

'Astronauts' in conversation during the Mars Society Australia’s Mars Robot Challenge Expedition.

Lessons Learned� e expectations of the expedition were fully met, as the capabilities of the robots and their creators were tested to the limit and beyond. Circuit boards that worked in the lab and workshop shorted out in the dry and dusty conditions. Wheels were shredded by

the rocky ground. Vibrations and bumps broken connections. Wind and rain disrupted operations and destroyed test equipment.

Expeditioners worked late into the night repairing equipment, building whole new circuit boards and devising work-around procedures. A blizzard of

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Outback Mars

Jonathan Clarke is president of the Mars Society Australia, and a geologist of more than 30 years experience. � e Arkaroola Mars Robot Challenge was his seventh expedition, the third as co-ordinator.

emails within the support network provided essential advice, and there were emergency deliveries of key components.

Working in parallel with the engineers were the scientists. � e rocks at Arkaroola are thought to record some major events in the history of life on Earth, including the early evolution of sponge-like animals. A team from Macquarie University sampled these rocks for ‘biomarkers’, organic molecules that might prove or disprove this hypothesis. � ey also worked

alongside the engineers to assess the scienti� c validity of the geological data collected and tested the ability of people in spacesuits to recognise stromatolites — dome-shaped fossilised structures formed by the kind of microbes that some think we might � nd also fossilised on Mars.

It is going to take months or years to fully adsorb the lessons from the expedition and publish the results. But some are already evident, such as practical lessons in the design and construction of functional � eld robots.

Other preliminary results are beginning to emerge. For example, small ground robots are not able to keep up with astronauts even over smooth terrains — they would be best deployed and le� to carry out independent operations, whether autonomously or by remote control. Much larger robotic vehicles will be needed with similar rates of movement to humans, and cross-country abilities will be essential.

Small airborne drones, through their speed and freedom of movement, have enormous potential to support human operations… such as scouting and enabling supervision and control of activities. But matching the capabilities of terrestrial multi-rotor drones for use on Mars, say, or Titan, is going to be a

challenge for aerospace and robotics engineers.

� ere were other valuable lessons learned, such as having diverse groups with di� erent backgrounds and goals working together on the same project. Participants developed relationships and networks whose potential may be realised only in years to come. And there were tremendous opportunities for engaging the public at Arkaroola as people attended lectures given by the expeditioners and stopped by to watch the tests.

� e mark of a successful expedition is the enthusiasm that those who were involved show for the next one. Mars Society Australia is exploring the possibility of a robotics competition to be held at Arkaroola, as well as further collaboration with Mars Society India. We're always looking for further members and volunteers for key roles in our expeditions, so please join us (www. marssociety.org.au) as we build the capability to expand the human race's future to Mars and elsewhere in the Solar System. �

A self-portrait of NASA's Curiosity rover on Mars.NASA/JPL-CALTECH/MSSS

Expedition robots. Left to right: Corobot and Mascot (Murdoch University), Miner and Big Blue (Mars Society Australia), Mars Society India and UNSW rovers. Overhead is Mars Society Australia’s Phantom 2 quadcopter.

'Astronauts' launch the Phantom 2 quadcopter to collect video data of the expedition for later analysis.

The Arkaroola Mars robot challenge expedition would not have been possible with the co-operation of the entire team and the numerous organisations that provided fi nancial or in-kind support: CSIRO, Australia-India Council, Macquarie University, Murdoch University, UNSW, Saber Astronautics, Arkaroola Wilderness Sanctuary, Victorian Space Science Education Centre and Mars Society Australia.

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22 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Comet Landing

Mission accomplished

Europe's Philae lander successfully touched down on 67P/Churyumov-Gerasimenko on

November 12, 2014, becoming the first craft ever to soft-land on a comet. And even though it experienced a couple of now-famous bounces before finally coming to rest, and despite ending up in a less-than-ideal mostly shaded spot, it managed complete its primary aims of testing the comet's ice and sending back images. Unfortunately though, without enough sunlight to keep it powered, Philae soon fell silent.

Meanwhile, the mission goes on for the Rosetta parent craft as it slowly circles the comet. The pair will travel side-by-side as they get closer to the Sun, giving Rosetta a box seat as sunlight transforms the wanderer's icy surface into an outpouring of gas and dust. ✦

Philae finds a new home

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The view from one of Philae's cameras while the lander was still attached to the Rosetta parent craft in October. Their target, comet 67P/Churyumov-Gerasimenko, is 16 kilometres away in the distance. ESA / ROSETTA

Philae's target landing site (grey crosshairs) was chosen for its smooth surface and life-giving sunlight.ESA / ROSETTA / MPS FOR OSIRIS TEAM

Philae, seen from Rosetta, on its own and descending towards the comet's surface. ESA / ROSETTA / MPS

FOR OSIRIS TEAM

Rosetta snapped these images of Philae as it descended, touched down and bounced back away from the surface. The bounce saw it sail one kilometre back up into space before descending again, bouncing one more time (not quite so high) before finally settling. ESA / ROSETTA / MPS FOR

OSIRIS TEAM

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Telescopic Toil & Trouble

JONATHAN FORTNEY

UNDER SCRUTINY Face down (bottom), a secondary mirror for the Large Binocular Telescope is checked in the lab. The 672 tiny magnets spread over its backside deform the surface to compensate for atmospheric effects. The upper portion (top) holds the devices that control the magnets. R. CERISOLA / LBT

FlawedGiantsThe world’s largest

optical telescopes have had to overcome serious

hurdles, delaying their scientific success.

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Arizona, and in 2008 by the 10.4-metre Gran Telescopio Canarias (GTC) in the Canary Islands.

These five observatories top the list of the world’s biggest optical telescopes. Yet, only the Keck telescopes have not had significant technical and management issues, and even Keck has seen failure with its effort to turn its two telescopes into an interferometer.

The Keck Interferometer sounded like it had enormous potential, combining two 10-metre telescopes into a single telescope with the resolution of an 85-metre mirror. For years the press releases from the Keck Observatory as well as from NASA raved about the possibilities. As Paul Swanson, project manager for the Keck Interferometer at JPL, said in 2001, “This is a major step in the creation of a whole new class of astronomical telescopes that will have an enormous impact on future knowledge.”

Ten years later, with the interferometer still not fully operational, NASA announced that it would no longer fund the project, and

For the last two decades the world’s astronomers have been tantalised by the construction

of one new record-breaking, ground-based behemoth telescope after another. Each was heralded as the telescope of the future, able to outperform the Hubble Space Telescope, peer into the distant past to solve the mysteries of dark matter and dark energy, and reveal the puzzles of stellar evolution and the formation of planetary systems.

Yet, as each one neared completion, the publicity and news coverage would slowly peter out. Years would pass without any game-changing scientific discoveries coming from these leviathans.

What had happened? We decided to find out, and what we have learned is that these telescopes are far more difficult to build than their press releases have suggested.

“These are huge industrial machines,” explains Gerard van Belle (Lowell Observatory), one of several instrument architects involved in the effort to combine the two 10-metre Keck telescopes in Hawaii into a single giant interferometer — until the interferometry project was shuttered in 2012. “It is like playing Whac-A-Mole. You fix one problem, and another pops up somewhere else.”

These sobering facts sound a warning for the much-touted next generation of even larger telescopes: things might not turn out as rosy as their press releases suggest.

Too Much of a Good ThingIn the last three decades the field of ground-based astronomy has undergone a revolution of design and construction. Beginning with the first-generation design of the Multiple Mirror Telescope (MMT) in 1979, astronomy has seen a plethora of new giant telescopes come online. The two Keck 10-metres in Hawaii, which saw first light in 1993 and 1996, proved that large-scale telescopes could be built and produce good science.

Keck was soon followed in 1996 by the 9.2-metre Hobby-Eberly Telescope (HET) in Texas, in 2005 by the 9.8-metre Southern African Large Telescope (SALT) in South Africa and the first of the two 8.4-metre mirrors of the Large Binocular Telescope in

Keck I Keck II

TWIN EYES Keck I and II on Mauna Kea were designed to work in tandem with four smaller scopes as an interferometer (top). Although NASA ultimately canceled the interferometry project, the two 10-metre telescopes remain powerhouses in optical and near-infrared astronomy, producing exceptional science.

the observatory quietly shut the entire operation down.

The failure of this high-profile project was partly technical but mostly political. In order for the images from the two telescopes to be properly combined, it was necessary to build and install at least four smaller, 1.8-metre-sized “outrigger” telescopes in a network surrounding the two main 10-metre telescopes.

These additional telescopes, however, were initially opposed by members of the native Hawaii population who consider Mauna Kea site to be sacred. They were also opposed by environmentalists, who, even after local Hawaiians gave a green light to the outriggers, filed suit against NASA and the University of Hawaii to demand an environmental impact assessment before construction continued.

Then the outrigger funding dried up in 2006. NASA had paid for the interferometer, along with similar research at LBT, as support for two planned space telescopes aimed at hunting for exoplanets: the Space

S&T: GREGG DINDERMAN

NASA / T. WYNNE / JPL

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Telescopic Toil & Trouble

In addition, the mirror segments were not parabola-shaped but spherical. The design limits the effective aperture, meaning that HET doesn’t use its primary’s full 11 metres. This curve also does not produce very sharp images, but it is far easier to build, as every segment can be identical. Because of this, the telescope was optimised for spectroscopy, which doesn’t need pretty pictures.

Unfortunately, HET experienced serious focusing and resolution problems right from the beginning and which lasted for years. “When we came on sky it was immediately obvious that we were making terrible images and we couldn’t hold them,” explained Gary Hill (McDonald Observatory, University of Texas at Austin).

The coatings on the segments deteriorated more rapidly than expected. The temperature in the telescope’s dome was too hot, causing mirror distortions. The 91 segments were difficult to align, and even once finally in place they would lose that alignment quickly.

It took about a decade to fully work out these bugs. The effort included not only major upgrades to the dome, but also to the sensing equipment that monitored and positioned the mirror segments, and to the instruments themselves. Engineers applied new coatings to the segments and established a more thorough and regular cleaning regimen for them.

Even these efforts did not make HET the instrument its builders had

For reasons that initially baffled its builders, the images the Southern African Large Telescope produced would randomly range from perfect to horribly smudged.

Interferometry Mission (SIM) and the Terrestrial Planet Finder. But in 2006 NASA tabled TPF and cut funding for the outriggers; in 2010 it also decided not to go ahead with sponsorship of SIM. With both of these missions cancelled, and with Keck continuing to face legal and logistical problems, NASA decided to cut its support, essentially ending the project.

Fortunately, this shutdown had little impact on the overall success of the Keck Observatory. Its two 10-metre telescopes remain functional and among astronomy’s best success stories.

The world’s other giant telescopes, however, have not fared so well.

SALT in the WoundThe Southern African Large Telescope (SALT) was going to put South African astronomy on the map. In order to build a world-class telescope on a limited budget, its builders decided to emulate the design of the Hobby-Eberly Telescope (HET) in Texas.

HET’s 9.2-metre effective aperture is the world’s fifth largest, but the telescope itself cost only US$16 million to build, a fraction of the cost spent on the other giants. To save money, the telescope’s mirror of 91 hexagonal segments was mounted on a rotating platform at a fixed zenith angle of 35°. Operators could rotate it but not tilt it. Instead, the instrument package, mounted on a frame above the mirror at its focal point, would move, tracking objects as their reflection traveled across the mirror’s face.

originally hoped it would be. Thus, in 2009 McDonald Observatory decided to do a major rebuild of the telescope and a significant revamping of its fundamental research effort. Rather than make HET an all-purpose spectroscopic observatory, they would treat it like a NASA astronomical probe similar to the Kepler discovery-class mission, with a specific, single research goal and instruments designed for that goal.

FACE LIFT In Operation Chrome Dome, engineers at the Hobby-Eberly Telescope resurfaced the entire dome with aluminium tape. The tape reduced the dome’s radiative cooling at night, improving seeing.

BIG BONES HET’s structure dwarfs most telescopes — and people. Seated at HET’s base during the structure's fabrication are the then-director and associate director of McDonald Observatory.

The goal chosen is dark energy. By installing the world’s largest collection of multi-object spectrographs and increasing the telescope’s field of view — to about half the area of the full Moon — they hope to compile a gigantic database of the redshifts of a million galaxies from about 11 billion years ago. When these data are compared with other similar surveys covering different cosmic epochs,

THOMAS A. SEBRING / HET CONSORTIUMJOHN GOOD

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HET’s scientists hope they will be able to better quantify the universe’s expansion rate and how dark energy has caused it to change over time.

This US$40 million overhaul — more than twice the telescope’s initial cost — is just wrapping up. The telescope will begin three years of observations aimed solely at this single research objective. Hopefully this approach will allow HET to finally produce science at the level dreamed of by its creators.

SALT, meanwhile, was completed in 2005, designed similarly to HET but with HET’s known bugs eliminated. Unfortunately, there were the unknown bugs. For reasons that initially baffled its builders, the images SALT produced would randomly range from perfect to horribly smudged. The situation became so serious that at one point Darragh O’Donoghue, the head of the effort to fix the telescope, bluntly noted at a technical conference in 2010 that

“unless the problem is solved soon, the telescope will be seen as a failure.”

Fortunately, after several years of complex detective work the team pinpointed the focus problem. Because the curve of the telescope’s mirror segments were like HET (spherical rather than parabolic), both telescopes’ designers needed to correct images for spherical aberration. To do this, an instrument called the spherical aberration corrector (SAC) refocused the light coming off the mirror and then sent that light to the scientific instruments. The two telescopes’ SACs had different optical designs (and therefore gave the scopes different effective apertures), but had the same purpose.

SALT’s problem was that its SAC’s steel frame was bolted to an aluminum ring, which in turn was glued into the carbon composite structure of the instrument payload. These three

materials all expand differently when heated and contract differently when cooled. The combination introduced a gigantic amount of unwanted thermal and mechanical stress in the SAC, ruining its mirrors’ alignment.

These repairs were only completed in 2010. Since then the telescope has been operating successfully, but time will tell if it will meet its specifications. For example, the telescope still lacks a working active-alignment system for its mirror segments, requiring operators to do manual alignment twice per night. This reduces observation time and also limits the length and precision of many of the telescope’s observations.

Double VisionThen there is the Large Binocular Telescope (LBT). First proposed almost three decades ago in 1986, the concept called for combining the light from two 8.4-metre mirrors mounted side-by-

OPEN WIDE Members of SALT’s image quality team prepare to test and realign the mirrors of the spherical aberration corrector (big tube). Stresses on the instrument had shifted the mirrors awry, producing images that were sometimes sharp and sometimes smudged (see next page). LISA CRAUSE

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side like a gigantic pair of binoculars to produce the equivalent light-gathering power of a 11.8-metre mirror and the resolution of one more than 22 metres across.

Construction was delayed almost a decade because of objections by environmentalists and the local Apache Indians. The environmentalists were worried about the telescope’s effect on

the endangered red squirrel that lives on the mountaintop of Mount Graham, while the Apaches said the mountaintop was sacred and therefore should have no new construction. It took a special exemption passed by Congress and a lot of wrangling to get the construction finally approved.

Then, once construction began in 1996, it took far longer than expected.

As with the other large telescopes, there were engineering issues. For example, in order for the telescope to view the entire sky, the building that houses it, weighing 2,000 tonnes, rotates on four multi-wheeled units called bogies that roll on a circular track. Construction engineers soon found significant engineering problems with this system. The rail the bogies ran on was wearing out faster than expected. Moreover, one wheel’s outer bearing had failed, and all the other wheels’ outer bearings were on the verge of failure, requiring their complete replacement.

Engineers also learned that one bogie was slightly offline. (Imagine one of the rear wheels of your car pointing sideways slightly, rather than straight ahead.) To get it realigned required jacking the entire 2,000-tonne building up slightly so that they could force it back into the correct position, silencing its popping and banging noises.

The telescope itself had other problems. For example, the its instruments are moved into position at the end of deployable swing arms. The

STARGAZING GIANTS Left: Seen here in 2005 are SALT’s dome and alignment system (tower in foreground). Right: The Large Binocular Telescope houses two primary mirrors in its boxy structure. Both LBT and SALT faced significant delays, but are now both up and running.

BEFORE AND AFTER Stars imaged before the repair of SALT’s spherical aberration corrector (left) look smudged. After the repair, the stars looked properly pointlike.

JANUS BRINK BABAK TAFRESHI

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use of these arms enabled the operators to switch out di� erent instruments easily during an observing run. Unfortunately, the arms had di� culty damping out vibrations caused by wind and other disturbances.

In addition, the oil and grease used on the giant track that tilted the telescope would get sprayed onto the mirrors when the telescope’s ventilation fans turned on. Keeping the fans o� eliminated this spray, but that made it di� cult to stabilise the telescope’s temperature for observations.

But all these technical engineering problems were relatively routine issues: they are the typical shakeout problems experienced by giant telescopes. What really delayed LBT from producing the expected science a� er � rst light in 2005 was the late arrival of almost all of its scienti� c instruments, which because LBT is a binocular telescope, come in pairs.

For example, the second of the telescope’s two optical spectrographs, the Multi-Object Double Spectrographs (MODS), was only installed on the telescope in the spring of 2014, almost a half-decade late. “� e MODS team had never built anything this big before,” explained Christian Veillet, LBT’s director. “I think they underestimated the time and challenges required.”

Similarly, the telescope’s two infrared spectrographic cameras, called LUCI 1 and LUCI 2, arrived in 2010 and 2013, years behind schedule. “I think the scope of the project and its complexity was once again underestimated,” says Veillet. “� e team also did not have much experience building this kind of cryogenic instrument.”

It was only in 2014 that all of the LBT’s � rst-generation instruments were � nally installed on the telescope. � ey are currently in the commissioning phase and should be available for science users by

BEARING WOES In order to make LBT’s bogies follow a circular track, engineers tilted the wheels 2.5° from the vertical. But this tilt put too much force on the wheels’ outer bearings. Engineers cut the old outer bearings out and replaced them with larger ones (shown in the left side of the schematic). PHOTO: ROBERT ZIMMERMAN; SCHEMATIC: S&T: GREGG DINDERMAN,

SCHEMATIC SOURCE: JAMES HOWARD / LBTO

BIG BUG Two 8.4-metre primary mirrors combine to create the alien-looking binocular telescope. ENRICO SACCHETTI / INAF

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mid-2015. Although science has already been coming out of LBT, project members now hope that the telescope’s scientific output will finally ramp up to its expected level.

Part of the reason these instruments were so late in coming was the chaotic management structure that formerly existed at LBT. Financed and built by partner institutions in the U.S., Germany, and Italy, the telescope project had no strong central management authority. For example, the partners were each in charge of building their own scientific instruments, with the observatory having little say in their design. “We don’t know anything about them,” explains Veillet of the instruments. “They arrive as black boxes.”

Because of all these issues the

telescope partnership decided in 2013 to hire Veillet as director and gave him the authority to manage the telescope properly. As one scientist told me at the first LBT users’ meeting, organised in March 2014 by Veillet in Tucson, Arizona, “Things are much better now with Veillet.”

Big BirdLastly there is the Gran Telescopio Canarias (GTC), on La Palma in the Canary Islands. The world’s largest parabolic telescope, with an effective aperture of 10.4 metres, the GTC was only completed in 2008, making it the youngest of this generation of giant telescopes. Thus, it is finishing out the initial shakeout period expected for all such big telescopes, lasting on average four to six years.

In the case of GTC, most of its problems have centered on maintaining the proper temperatures for two of the telescope’s main instruments.

Soon after commissioning in 2008, telescope engineers found that the CCD of the telescope’s main optical camera, OSIRIS, was much warmer than planned. In order for the camera to detect objects with magnitudes as faint as 28 in a reasonable amount of observing time, the CCD must be cooled to 170 kelvin so that its own heat doesn’t drown out the object’s signal.

The problem was that the dewar, the cryogen flask designed to cool the CCD, wasn’t doing the job. As the telescope’s website notes, the system required “continuous baby-sitting to ensure that temperature and pressure

BIG BIRD Like its giant brethren, the Gran Telescopio Canarias dwarfs people. With an effective aperture of 10.4 metres, GTC is one of the largest optical telescopes in the world. BABAK TAFRESHI

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Contributing editor Robert Zimmerman’s classic history of the 1960s space race, Genesis: The Story of Apollo 8, is now available as an eBook. When he isn’t visiting giant telescopes, he writes daily at http://behindtheblack.com.

remained within operational bounds.”To fix the problem, the observatory

first built a temporary dewar to replace the one that was not working. When this was installed in 2010, the situation improved. The original cryostat was taken apart and inspected, whereupon it was discovered that heat was being conducted from the outside world into the CCD at three contact points. Once engineers replaced the stainless steel contacts with insulation, the dewar was finally able to function correctly.

Then in 2013 a similar problem occurred with the telescope’s infrared instrument, CanariCam. In this case the system for cooling the instrument, called a cold head, was supposed to have a life expectancy of one year. “In practice the cold head wouldn’t survive in operating conditions more than five months, sometimes not more than two months,” explains Pedro Álvarez Martín, GTC’s director. “The provider has been unable to correct the problem.”

A permanent fix will require replacing the system entirely. In the meantime the observatory has obtained a number of spares and switches them out when necessary. “We live with a heavy load on our operations team,” adds Martín. “Each CanariCam service requires a week of instrument down time.”

On top of these engineering issues the telescope has had the typical start-up funding problems. Because of 2009 cuts to the science budget in Spain, the telescope’s biggest partner, the

observatory was forced to stretch out development of the telescope’s second-generation instruments, producing “a considerable slippage in our initial plans,” according to Martín.

With these initial shakeout problems now under control or solved, GTC’s scientific output should begin to ramp up to more expected levels in the next few years.

The FutureWhat do these stories tell us about the next generation of giant ground-based telescopes like the Giant Magellan Telescope (GMT), the Thirty Metre Telescope (TMT), and the European Extremely Large Telescope (E-ELT), which are now in their initial design or construction phases? Will their future be the same, with similar difficulties?

The history here suggests yes. All these telescopes have faced similar problems. For example, the present generation of big telescopes all began their lives with either very tight or insufficient budgets, or some form of budget cuts. None had sufficient funding to keep instruments’ builders on staff during the transition to

operations so that they could train the operations staff properly. “The amount of funding never quite ensures a long enough overlap,” notes Hill. “This is a lesson that the big future telescopes had better be careful about.”

Sometimes only a little more money was needed to fix things. For example, engineers built HET for US$16 million, but to straighten out its worst problems only cost another US$4 million.

Other times, however, the completion costs have been vastly higher. Even with HET, designers eventually decided that the US$4 million repairs were insufficient, opting for a complete US$40 million overhaul. The worst examples of this kind of cost overrun have been seen with space telescopes, including both the Hubble Space Telescope and the upcoming James Webb Space Telescope. There, the overruns were so large that at some point both projects were threatened with shutdown.

Thus, no one should be surprised if the next generation of giant ground-based telescopes — the E-ELT, the TMT, and the GMT — have serious growth pains. Each might take several years of trial and error before it can produce sharp images and begin churning out the really spectacular astronomical discoveries.

These telescopes, however, will be on the ground and accessible for redesign and repair. The one terrifying thought that kept reappearing in my conversations with engineers and astronomers is, what will happen if Webb requires the same kind of shakeout? Located more than a million kilometres from Earth, it might develop problems engineers haven’t weeded out in their zealous tests, and the most expensive telescope ever built might end up becoming nothing more than a hunk of metal, useless to anyone.

But however easy the accessibility to scopes on the ground, the engineers and managers of the giants of the future will likely still find themselves scrambling about madly, “whacking moles” as they struggle to get their telescopes up and running.

The worst examples of this kind of cost overrun have been seen with space telescopes, including the Hubble Space Telescope.

ABOVE THE CLOUDS The Gran Telescopio Canarias sits on the island of La Palma in the Canary Islands. It is still in its initial shakeout phase but is producing science results. BABAK TAFRESHI

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Deep Fields

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Deep Fields

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GOVERT SCHILLING

The Hubble Space Telescope, which will celebrate its 25th anniversary in April 2015, is the symbol of our era for every astronomer. Orbiting above the

distorting effects of Earth’s atmosphere, it has provided unprecedented views of star clusters, nebulae and galaxies. Using its suite of sensitive cameras and detectors, and focusing on ‘blank’ patches of sky, Hubble has also revealed the building blocks of galaxies so far away that their light took many billions of years to reach us.

But cosmologists want to reach even farther. And since they can’t swap Hubble’s 2.4-metre mirror for a larger one, they’re now seeking assistance from nature’s own zoom lenses. Using the gravitational-lensing effects of six remote clusters of galaxies, the new Frontier Fields program aims to push back Hubble’s limits and study the true dawn of galaxy formation. “We’re going deeper than ever before,” says principal investigator Jennifer Lotz of the Space Telescope Science Institute (STScI).

Last March, at a conference in Rome, Lotz presented the first results of the new program. Her showpiece is a November 2013 Wide Field Camera 3 (WFC3) image of Abell 2744, nicknamed Pandora’s Cluster. But a second cluster, MACS J0416.1-2403, has also been observed by Hubble’s Advanced Camera for Surveys (ACS). In the winter of 2014, WFC3 was aimed at MACS J0416, while ACS observed Abell 2744. In 2015 Lotz’s team will target

HubbleGoes the Distance

FRONTIER FIELD 1 Left: The gravity of the giant galaxy cluster Abell 2744 (Pandora’s Cluster) distorts and magnifies the images of small, faint background galaxies.

PARALLEL FIELD Right: When astronomers first aimed Hubble’s Wide Field Camera 3 at galaxy cluster Abell 2744 to take Frontier Field 1, the telescope's Advanced Camera for Surveys was pointed nearby to image a parallel field. Later, the roles were reversed so that both fields were covered by the multiple wavelengths of both cameras. Scientists use the parallel field as a basis for comparison. Above right: The size of the ACS camera field is shown in blue; that of the WFC3 field in red.

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Frontier Field 1Parallel Field

Using nature’s gravitational lenses, astronomers are pushing the Space Telescope to its very limits to reveal primordial galaxies.

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Deep Fields

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GRAVITATIONAL LENSING The Frontier Fields program takes advantage of gravitational lensing, an e­ ect predicted by Einstein’s general theory of relativity that astronomers have already observed in a variety of contexts. Thanks to relativity, the gravity of a massive foreground object (in this case, a galaxy cluster) serves as a lens — redirecting toward Earth some of a background object’s light that would otherwise miss us. Gravitational lensing thus magnifi es the background object (though also distorting it), enabling telescopes to spot distant galaxies that would otherwise fall below the detectability threshold. S&T: LEAH TISCIONE

EXTREME DEEP FIELD Astronomers assembled the eXtreme Deep Field (XDF) by combining a decade of Hubble images of a tiny, 2-by-2.3 arcminute patch of the southern constellation Fornax. It contains about 5,500 galaxies at various distances, mostly small blue young ones. The data come from the Advanced Camera for Surveys and Wide Field Camera 3. The XDF is the deepest image yet taken, and reveals galaxies that existed as early as 500 million years after the Big Bang. NASA / ESA / G. ILLINGWORTH, ET AL. / HUDF09

two other clusters with both cameras, and in 2016 the program is scheduled to conclude with observations of a � � h and sixth cluster. A whopping 140 orbits worth of precious Hubble observing time will be devoted to each of the six � elds.

By studying remote galaxies that are gravitationally magni� ed and brightened by the foreground clusters’ gravity, Lotz and her colleagues can study objects that are intrinsically fainter than would otherwise be possible to see. � e team expects to obtain a more representative view of the galaxy population in the newborn universe. “We want to carry out a statistical study of the early formation history of galaxies,” says Lotz. “When did the lights in the universe come on? How many galaxies were formed within the � rst few hundred million years? Was the formation of the � rst galaxies a very gradual process, or did it happen more suddenly? To answer these questions, we need to go 10 times deeper than before.”

NASA’s Spitzer Space Telescope and Chandra X-ray Observatory, as well as large ground-based telescopes, are making supporting observations of the Frontier Fields. In the Abell 2744 data, one group found that the number of galaxies drops signi� cantly beyond a redshi� of 8.5 or so (corresponding to a cosmic age of 600 million years). And two groups each recently found a galaxy at a redshi� of 9.8, corresponding to a time only 490 million years a� er the Big Bang.

Pretty Picture to Treasure TroveTwenty-� ve years ago, few could have imagined that long-exposure observations of ‘empty’ � elds would yield exciting new results. “In a 1990 Science publication, Princeton astrophysicist John Bahcall wrote that he did not expect such deep observations to reveal a new population of galaxies,” recalls Bob Williams, who directed the STScI between 1993 and 1998. “In 1995, when we embarked on the original Hubble Deep Field program, both Bahcall and Lyman Spitzer, one of the fathers of the Hubble Space Telescope, were strongly opposed to the idea. � ey worried about the public response, since there was no guarantee of scienti� c success.”

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Foreground stars

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Extremely distant galaxies

TUNNEL THROUGH TIME All the Hubble deep field images are tunnels through time, capturing objects from relatively nearby Milky Way stars to primaeval galaxies whose light has taken 13 billion years to reach us. The labels identify different types of objects appearing in Frontier Field 1. NASA / ESA / J. LOTZ / M. MOUNTAIN / A. KOEKEMOER / HFF TEAM (STSCI)

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Deep Fields

Back then, Hubble’s public image was indeed something to worry about. � e primary mirror’s spherical aberration had just been corrected — 3½ years a� er launch — and many people (and politicians) saw Hubble as a costly, underperforming astronomy toy. Why would anyone devote 150 orbits worth of observing time to study an empty region of the sky? But Williams knew better. Recent long-exposure Hubble images taken by Mark Dickinson (now at the National Optical Astronomy Observatory) had shown misshapen ‘train-wreck’ galaxies at a redshi� of 1.2, corresponding to a look-

back time of two-thirds of the age of the universe. “� is to me was transformational,” says Williams.

At a morning co� ee meeting in the Institute’s library, Williams and his colleagues � rst brainstormed the idea of a Hubble Deep Field. “We were really excited. Everything was up for discussion,” he recalls. “Should we do one � eld or many? Should it be targeted at known objects or should it be blank? Which � lters would be the best to use? When would the data be released to the astronomical community and to the public?” An outside advisory committee failed to reach a consensus,

and in the end, Williams decided to spend a huge chunk of his director’s discretionary observing time — a total of 141 hours — on observations of a small, relatively empty patch of Ursa Major. “It had to be done,” he recalls, “so we did it.”

Hubble’s Wide Field and Planetary Camera 2 (WFPC2) obtained the 342 separate exposures (in four wavelength bands) between December 18 and 28, 1995, and a mere 17 days later, the fully reduced data set was made public. � e iconic image revealed more than 2,000 individual galaxies, most of them at very large distances. “In retrospect, it

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THE SIX FIELDS The Frontier Fields Team targeted six patches of sky for their program. Unlike previous Hubble deep fi elds (HDF-N and -S, HUDF), which were selected for being relatively empty regions, the Frontier Fields all have foreground galaxy clusters that act as gravitational lenses. SOURCE: HFF TEAM (STSCI)

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They have shown us the early history of cosmic processes that have ultimately led to the origin of humanity.

was a huge success,” says Williams, “especially when spectra of 130 remote galaxies were taken over the subsequent three years by the Keck telescope. Keck turned the Hubble Deep Field from a pretty picture into a scientific treasure trove.”

Deeper and DeeperA galaxy’s spectrum yields its redshift, and the redshift reveals how long the galaxy’s light has been traveling through expanding space. In other words, spectra turn deep-field images into 3-dimensional core samples of the early universe. Unfortunately, spectra

Hubble Deep Field galaxies, astronomers significantly increased the precision. In fact, the technique has been extended to 30 or more bands. “It’s almost like obtaining a low-resolution spectrum,” says Williams. “To me, the validation of the concept of photometric redshift is the single most important result that emerged from the Hubble Deep Field and its successors.”

Indeed, the new Frontier Fields program is far from the first campaign to follow in the footsteps of the original Hubble Deep Field. In September and October 1998, WFPC2 imaged the Deep Field South, in the constellation Tucana, which was simultaneously observed by Hubble's Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). Next came the Hubble Ultra-Deep Field (2003-04), with its infrared extension in 2012, and the Hubble eXtreme Deep Field (2012). Meanwhile, projects such as GOODS and CANDELS provided astronomers with somewhat shallower data over wider fields of view. And of course, the various Hubble Deep Fields have also been studied in detail by other space telescopes such as Chandra and Spitzer to obtain X-ray and mid-infrared images.

“These are marvelous programs yielding fascinating results,” says Williams. For example, the deep-field programs have shown that half a billion years after the Big Bang, the universe’s star-formation rate was quite low, but then it ramped up several orders of magnitude until it

reached a peak when the universe was some 2.5 billion years old. They also indicated that there must have been large numbers of hot but low-luminosity objects in the early universe — probably enough to explain the reionisation of intergalactic matter at a time when the universe was less than a billion years old.

And, of course, they have revealed the most distant galaxies yet found, including the current record holders, known simply as MACS0647-JD and UDFj-39546284, which are probably both at a redshift of 10 or 11. According to Williams, “Our current knowledge of the distant universe is largely based on the succession of deep fields. They have shown us the early history of cosmic processes that have ultimately led to the origin of humanity. Understanding these processes will make humanity much more comprehensible to all of us.”

The Deepest ViewsSo how can astronomers improve on what Hubble has done so far? In the summer of 2012, then STScI director Matt Mountain found himself discussing the prospects for yet another deep-field campaign with Hubble Mission Head Ken Sembach. After consulting a Hubble science working group and various experts within the scientific community, the concept of the Frontier Fields program emerged — a name that was coined by Sembach. “The question was: Can we do better than the Hubble Ultra-Deep Field?” says Lotz. “The answer was: yes, if we use Hubble in tandem with one of nature’s own telescopes, and repeat the feat six times.”

Using gravitational lenses will give astronomers “a sneak peek at the JWST universe,” says Lotz, referring to Hubble’s infrared successor, the 6.5-metre James Webb Space Telescope, scheduled to launch in late 2018. During each observing run, one of Hubble’s main cameras (ACS and WFC3) will be trained at a carefully selected cluster of galaxies, while the other camera will observe a neighbouring blank field. Half a year

COMING SOON These images show the other five planned Frontier Fields. All feature massive galaxy clusters whose gravitational lensing will reveal extremely faint galaxies in the early universe. NASA / ESA

/ J. LOTZ /M. MOUNTAIN / A. KOEKEMOER / HFF TEAM (STSCI)

can be obtained only for relatively bright objects, so the distances of the faintest galaxies in the Hubble Deep Field remained unknown. That is, until Chuck Steidel (Caltech), Piero Madau (University of California, Santa Cruz), and others perfected the photometric redshift technique, in which a galaxy’s redshift can be estimated from its relative brightness in various wavelength bands.

This 1960s technique was originally quite inaccurate. But by developing better model spectra and comparing the results with the Keck spectra of

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later, the fields will be swapped, so each cluster and each blank field will be imaged at three optical wavelengths with ACS and at four infrared wavelengths with WFC3.

Observations of the blank parallel fields are necessary because astronomers are concerned about cosmic variance. “On average, the universe looks the same everywhere, but not exactly the same,” explains Lotz. “The Ultra-Deep Field was just one pointing, so we will now add six other blank-field pointings as a control sample.” But the earliest and most distant galaxies are expected to be found in the cluster fields, where gravitational lensing might magnify their feeble radiation by tenfold or — in very rare cases — even a hundredfold. “Ours won’t be the deepest images,” says Lotz, “but they will provide by far the deepest view.”

The six clusters have been selected on the basis of the expected magnification they have to offer, on their apparent dimensions on the sky (they have to fit within the field of view of Hubble’s cameras), and on their locations: both the Keck telescope in Hawaii and the submillimetre ALMA Observatory in

Chile will be used for follow-up observations. Five independent groups have produced magnification maps of the clusters on the basis of existing observations, to carefully predict where lensed images of extremely faint background galaxies might show up.

In three years, Lotz’s team hopes to complete observations of all six Frontier Fields. By then, the project will have devoted a total of 840 orbits worth of Hubble observing time. At press time, only observations of the first four of the six fields have been approved; a committee will soon review the program and decide on whether or not to continue with the final two fields. Lotz is quite confident: “We may even add more fields in the future,” she says. “Hubble’s successor, the James Webb Space Telescope, may target these clusters in the future as well as better clusters that were not known when we selected the Frontier Fields.”

Scientific analysis of the first Frontier Fields observations is already in full swing. In a November 1st Astrophysical Journal paper, Wei Zheng (Johns Hopkins University) and his colleagues report the detection of 18 galaxies beyond a redshift of 7 in the Abell 2744

data, but none at a redshift of about 9 or higher. But they caution that more Frontier Fields’ data will be needed before a definitive claim can be made regarding a rapid buildup of galaxies by redshift 8.

But other groups found a triply lensed galaxy at a redshift of 9.8. This object is a mere 300 light-years across, making it 500 times smaller than our Milky Way. It’s basically a small clump of matter that’s just starting to churn out stars at a rate about one-third that of our galaxy, and also at a slower rate than the redshift-8 galaxies. The object was first discovered by a team led by Adi Zitrin (Caltech), which published its results in the September 5 online edition of The Astrophysical Journal Letters. It was confirmed independently by a team led by Pascal Oesch (Yale University); the results have been submitted to The Astrophysical Journal. The discovery might represent the tip of the iceberg of a large population of small galaxies that later merged to form the behemoths we see today.

The Frontier Fields program is really the best Hubble can do with deep-field observations. The quarter-century-old space telescope will not receive any more upgrades, and so won’t be equipped with any new cameras or detectors. But by teaming it up with nature’s own telescopes, astronomers can push it to its very limits. Bob Williams, the father of the original Hubble Deep Field, is impressed: “It’s great stuff. In some other disciplines, scientists can study remains from the past. But astronomy is the only science that really lets you witness the past.”

Contributing editor Govert Schilling is author of the new book Deep Space. He won the American Astronomical Society’s prestigious David N. Schramm Award for Science Journalism for “The Frozen Neutrino Catcher”.

PRIMORDIAL GALAXY Astronomers found this small, extremely distant galaxy in Frontier Field 1. Based on its brightness at different wavelengths, the galaxy, triply lensed above, appears to have a redshift of 9.8, making it one of the most distant objects ever seen. Its existence proves that small galaxies were assembling when the universe was only 490 million years old. NASA / ESA / A.

ZITRIN (CALIF. INST. OF TECHNOLOGY), AND J. LOTZ,

M. MOUNTAIN, A. KOEKEMOER, AND THE HFF TEAM (STSCI)

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Page 43: Australian Sky & Telescope -2015

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Page 44: Australian Sky & Telescope -2015

Astronomy Above the Clouds

TOM GALE

The clement cloak of gas that enshrouds Earth is truly a wonder. � e composition of our planet’s unique atmosphere arises in

part from a harmony of respiration and photosynthesis, performed by the organisms it shields from the deadly radiation and cold of space. Yet we skywatchers could be forgiven for harboring mixed feelings about this atmosphere. For the layers of gas above our heads distort the path of incoming light from space.

� at’s because the atmosphere is far from uniform. For example, adjacent air pockets can exhibit markedly di� erent densities and turbulent motions. � e overall consequence is that incoming light rays get refracted along a multitude of ever-changing pathways, as residual heat drives convection that ceaselessly churns up the nocturnal atmosphere.

Worse still, highly magni� ed images only serve to exaggerate the e� ects of atmospheric turbulence. Even on nights of relatively good seeing, we are usually plagued by the irksome shimmering of lunar craters and “boiling” star discs that jump around the telescopic � eld of view. Looking for delicate features in Jupiter’s cloud belts can be somewhat akin to trying to glimpse the scales of a � sh beneath a pond surface disturbed by a breeze.

In the last couple of decades, professional astronomers have tackled this problem with adaptive optics (AO), which quickly bend mirrors’ surfaces to compensate for the chaotically changing, churning atmosphere above. But even with AO systems, observatory planners must still pursue the tried-and-tested solution: get above as much of the atmosphere as possible.

Early RisersIn his book Opticks, Isaac Newton insightfully penned that “the only remedy is a most serene and quiet air, such as may perhaps be found on the tops of the highest mountains above the grosser clouds.” � e higher the viewpoint, the better the seeing conditions generally become, a trend conclusively demonstrated during Charles Piazzi Smyth’s expedition to Tenerife in 1856. � ere, the eccentric Astronomer Royal for Scotland, using a team of hardy donkeys, lugged a 7-inch telescope and other instruments to an elevation of 3,260 metres. Delighted by the sharp views he obtained and soon excited at the prospect of having a permanent mountain observatory built, Smyth recorded his observations in diligent detail in order to petition skeptical funding bodies back home.

Before Victorian times, there was no street lighting bleaching out the night sky, and so few thought to place the earliest astronomy centres anywhere but within easy reach of towns and universities. But by the late 19th century, light and

soot spewed out by rapidly expanding industry soon drove more skywatchers to the mountains. When American astronomers established the 36-inch refractor at Lick Observatory on California’s Mount Hamilton (1,280 metres) in 1888, the site became the world’s � rst permanently occupied mountaintop observatory.

Ever conscious of the advantages o� ered by high elevations, the solar astronomer and observatory pioneer George Ellery Hale was tempted by greater heights. He site-tested the lo� y summit of Pikes Peak (4,300 metres) in Colorado as early as 1893 but, on practical grounds, eventually opted for Mount Wilson’s modest elevation of 1,735 metres for the observatory he founded in 1904. Later to play host to the legendary 100-inch Hooker Telescope, Mount Wilson was key to developments in 20th-century astronomy, not least when Edwin Hubble used the 100-inch to discover that the Andromeda Galaxy was millions of light-years away, con� rming it was an “island universe” separate from our Milky Way Galaxy.

Rocky RetreatFollowing the establishment of the iconic 200-inch Hale re� ector on Palomar Mountain in 1948, clusters of domes rapidly sprung up atop other American summits. � e 1950s saw the founding of the National Observatory at Kitt Peak (2,100 metres) in Arizona, while the much higher lava � elds of Mauna Kea (4,190 metres) attracted their � rst big telescopes a decade later.

Each site marked an extra step away from encroaching light pollution and upward into the stable, moisture-depleted reaches of the upper atmosphere, a vital consideration for the increasingly important study of infrared wavelengths (see page 49).

Today, the Hawaii-based telescopes, including the leviathan twins of the Keck Observatory and the submillimetre-studying James Clerk Maxwell Telescope, are o� en crowned as the highest observatories on U.S. soil. But for that superlative we must instead turn to the Rocky Mountains. For in Colorado lies what was for several decades the highest optical telescope in the world: the Meyer-Womble Observatory. Named for both its designer and � nancier, the facility’s modest windswept dome houses an impressive binocular telescope with two 28.5-inch aperture components. Coordinated by Robert Stencel (University of Denver), Meyer-Womble sits just below the summit of Mount Evans which, topping out at a breathtaking 4,345 metres, is one of the Rockies’ highest peaks.

Long before optical telescopes arrived, a sinuous 22-kilometre access road to the summit attracted particle physicists keen to set up detectors at such an unprecedented elevation. Nobel laureate Arthur Compton’s extensive cosmic-ray readings

44 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Seen from an aircraft, La Silla Observatory in Chile looks forlorn against its cordilleran backdrop. At an elevation of approximately 2,375 metres, the site is one of many that astronomers have built in order to reach higher into the sky. ESO

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Into

Astronomers’ continual quest for optimal seeing conditions has ensured that leading observatories get built on ever-higher mountaintops.

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46 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Astronomy Above the Clouds

atmosphere. Early measurements of these unusual particles showed them to be arriving at relativistic speeds. Since lab experiments had showed that muons at rest decay rapidly, the surprising abundance of muons that Rossi recorded at ground level proved that the particles’ lifetime had somehow become prolonged. As he soon realised, this observation was a consequence and elegant demonstration of time dilation, a tenet of Einstein’s special theory of relativity.

More recently, data from Meyer-Womble proved key to revealing the dusty, particulate nature of the mysterious eclipsing object in the enigmatic binary system Epsilon Aurigae. Stencel harbours doubts about the future of small-scale, mid-latitude stations such as Mount Evans in a century gearing up for 30-metre aperture telescopes. But the site’s rich scienti� c history, together with upgrading and reinforcement following storm damage in 2011, will help ensure that Meyer-Womble provides professional-grade astronomical data for years to come.

Asian HideawaysAlthough most cosmic rays arriving at Earth stem from the Sun, a handful have made a far longer journey.

Astronomers studying these galactic and intergalactic cosmic rays o� en seek out observing locations farthest from the tightly clustered � eld lines at Earth’s magnetic poles. Installations include the Pierre Auger Observatory in Argentina (1,370 metres) and the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) Telescopes on the Canary Island of La Palma (2,195 metres). Southeast Asia is arguably the region best placed for cosmic-ray astronomy, because it lies on Earth’s magnetic equator. Here, terrestrial � eld lines sweep aside more incoming low-energy solar particles (up to 17 gigaelectron volts, or GeV) than anywhere else. � is means that relatively few solar particles make it through to the atmosphere, enabling more of those from deep space to reveal themselves to detectors atop Doi Inthanon, � ailand’s highest peak (2,560 metres).

“We don’t detect the rays themselves,” explains Alejandro Sáiz Rivera (Mahidol University, � ailand). “But the air shower of secondary particles includes neutrons. � ese don’t make it down to sea level, but up at Doi Inthanon we pick up the signals of around 2 million neutrons every hour.” Doi Inthanon is home to the group’s Princess Sirindhorn station, near

AN AMERICAN ICON Perched on Mount Hamilton, Lick Observatory was the world’s fi rst permanently occupied mountaintop observatory. Shown prominently here are the domes of the 36-inch refractor and 36-inch Crossley refl ector, both installed in the late 1800s. Inset: The dome of the 120-inch Shane refl ector, under construction in June 1951. PHOTO © UC REGENTS / LICK OBSERVATORY (2)

HARROWING HAUL During transport up Mount Wilson, the tube for the 100-inch Hooker scope nearly fell o� the road. Such scrapes are among the challenges of building at high elevation. THE OBSERVATORIES

OF THE CARNEGIE INSTITUTION FOR SCIENCE COLLECTION AT THE HUNTINGTON LIBRARY, SAN

MARINO, CA

from the summit in the early 1930s con� rmed that the detected number of cosmic rays increases with elevation. His data also helped reveal that the intensity correlated with geomagnetic latitude.

It wasn’t long before Mount Evans set the scene for another landmark experiment. In 1939 the Italian emigrant physicist Bruno Rossi recorded the � ux of muons, one of several subatomic byproducts generated when a cosmic ray collides with an atomic nucleus at the top of the

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Chiang Mai. Despite the particles’ cosmic sources, the neutron readings allow the team to indirectly detect solar storms: when the Sun releases a powerful flare toward Earth, the magnetic field carried by the flare deflects cosmic rays that would otherwise strike the planet. Sudden drops in the neutron count thus indicate disturbances in Earth’s magnetosphere. Such signals picked up at Doi Inthanon, with its unusually high geomagnetic cutoff energy, complement those of the 11 neutron stations set up at polar latitudes to monitor space weather in an ongoing international venture named Spaceship Earth.

Elsewhere in Asia, the Indian Institute of Astrophysics sought to make the most of the even higher terrain in its own backyard — the Himalaya Mountains. Although much of the Indian subcontinent experiences a prolonged monsoon, the carefully chosen site on Mount Saraswati (4,500 metres) in the Hanle Valley of Ladakh lies in a rain shadow cast by the highest Himalayan peaks. What’s more, K2 and the other peaks of Pakistan’s mighty Karakoram range dry out any rogue westerlies heading Hanle’s way, which further reduces the humidity.

“We get just a few centimetres of rain per year and less than 20 cm of snow,” explains Tushar Prabhu (Indian Institute of Astrophysics). The resulting dry, settled air at this elevation is a magical recipe for observational astronomy,

routinely offering 0.8-arcsecond seeing conditions. Today, Hanle boasts the 2-metre Himalayan Chandra Telescope, which scours the ultra-dark sky at optical (about 0.4 to 0.8 microns) and near-infrared (0.9 to 2.5 microns) wavelengths, conducting studies that range from cloud movements in Venus’ atmosphere to the behaviour of cataclysmic variable stars, stellar evolution in open clusters, and the monitoring of supernova remnants.

High and DryThe extreme elevation and arid climate of the Andes ensured that the world’s longest mountain range was among the first to draw the attention of scientists seeking out the planet’s optimal observing sites. Indeed, the first station at Chacaltaya was founded in the early 1940s, despite sitting at 5,230 metres. The station has long been remarkably accessible, requiring only a short approach road from the nearby Bolivian capital of La Paz. The highest observatory in the world for six decades, the Chacaltaya Astrophysical Observatory is a centre for cosmic-ray research and now houses several experiments, including the Investigation on Cosmic Anomalies (INCA), which detects the secondary particles that gamma rays create when they strike Earth’s atmosphere. Because the detector is at such a high elevation, it typically picks up a particle count 30 times higher than an experiment placed at half the

elevation would for secondary particles generated by 16-GeV photons.

Other nearby parts of South America are almost perfect for optical and infrared astronomy, thanks to the icy Humboldt Current that flows northward along the continent’s Pacific shoreline. Here, atmospheric moisture condenses out into fog banks that perpetually enshroud the coast. As a result, the region inland is one of the driest in the world — the Atacama Desert. There are towns near the Chilean coastal city of Arica where it rains less than once every decade, and a handful of villages where lifelong locals cannot remember ever having reached for an umbrella. The Atacama soil is so bone-dry that even highly water-soluble saltpeter can be dug from the ground as huge crystals — a valuable export commodity.

In fact, the infrastructure set up for mining has in part made the arid Atacama more accessible, enabling full exploitation of its dark-sky sites by establishing astronomical observatories in otherwise difficult and remote locations. The domes of Cerro Tololo, La Silla, and Cerro Paranal (all at 2,195–2,650 metres), the last one home to the Very Large Telescope, are renowned for their world-class seeing conditions and ultra-transparent skies.

Now astronomers are setting up observatories higher than ever before in the Atacama.

Despite the health risks of working at Polarbear (5,190 metres), ACT (also

CATCHING NEUTRONS The Princess Sirindhorn station in Thailand uses 18 tubes encased in polyethylene to detect neutrons formed by cosmic rays hitting Earth’s atmosphere. The tubes are filled with a gas enriched in boron-10 and surrounded by lead. The lead emits subatomic particles (mostly neutrons) when atmospheric neutrons hit it, amplifying the signal. Deep inside, the boron isotope splits when it captures a neutron, producing a signal. The 18-tube monitor weighs around 36 tonnes, about 30 of which is the lead. PIERRE-SIMON MANGEARD (2)

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Astronomy Above the Clouds

5,190 metres), and the jungle of ALMA’s 66 dishes (5,090 metres) on the Chajnantor Plateau, Tokyo University is reaching even higher. Planners boldly chose Cerro Chajnantor, a summit at a breathtaking 5,640 metres overlooking ALMA, for the University of Tokyo Atacama Observatory (TAO). Here, the air pressure is a mere 495 millibars, less than half that at sea level. TAO will legitimately boast being the � rst operational telescope sited above half the mass of Earth’s atmosphere.

� e Tokyo project is spearheaded by a 1-metre optical/near-infrared instrument dubbed “mini-TAO.” As a consequence of the extreme elevation, workers visiting Cerro Chajnantor must remain vigilant for symptoms of altitude sickness and not linger (see � e Silent Killer, next page). � ese risks are now greatly

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Tom Gale coordinates foundation-level chemistry teaching for University College London. A lifelong amateur astronomer, he is no stranger to high elevations himself and has climbed to 6,000 metres during snow treks in Nepal and Kyrgyzstan.

BARREN LAND The 2-metre Himalayan Chandra Telescope sits on the arid Mount Saraswati in India. The scope saw fi rst light in 2000 and is at one of the highest elevation observatories in the world. RAKESH RAO / ASTROPROJECT

PEEKING THROUGH THE GAPS Earth’s atmosphere blocks many parts of the electromagnetic spectrum, allowing only certain wavelengths through (grey). Water absorbs many of the infrared wavelengths, resulting in the 'transmission spectrum' seen above. The spectrum and the transitions between wavelength ranges are approximate; there isn’t a clear division between X-rays and gamma rays.

minimised thanks to the recently established capacity to remotely operate the observatory.

Following its � rst light in March 2009, mini-TAO soon picked up a key emission line in the spectrum of interstellar hydrogen gas at 1.875 microns, a near-infrared band known as Paschen alpha (Pα). � is detection, unprecedented by a ground-based instrument, would be impossible even from an Alpine summit due to blockage by the troublesome water vapour in Earth’ s atmosphere. Unlike visible light, Pα is hardly absorbed by interstellar dust, allowing astronomers to peek inside obscured parts of the Milky Way’ s most distant spiral arms. TAO researchers have since mapped the distribution of similar stellar nurseries in several dozen far-� ung starburst galaxies. Understanding their star-forming habits will

help shape new ideas about galactic evolution. Excitingly, this is just the beginning: mini-

TAO is merely intended as the observatory’s pilot instrument. It will soon be joined by its bigger brother, the centerpiece 6.5-metre telescope already under construction and set for � rst light in 2017. Other projects are also in the works. Even as astronomers dream of larger mirrors and savvier adaptive optics systems for projects closer to sea level, it’s hard to beat the conditions at these high-elevation sites. Astronomy the world over really is on the up.

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Go hiking in the Rockies or shu� e between its ski lifts and you’ll soon have to stop and catch your breath. Air pressure drops quickly as you ascend into the atmosphere (initially by 33 millibars per 330 metres gained), so that each breath you draw harvests fewer oxygen molecules for your lungs. You might not feel the reduction in pressure but, as you climb, packets of plastic-wrapped food expand to bursting and bottles hiss when opened as they exhale compacted air.

Rise beyond 3,000 metres and your breathing becomes markedly faster. Your bloodstream’s oxygen level drops and your rest pulse races as high as 100 beats per minute in an e� ort to compensate. You’ll likely experience fatigue, headache, reduced appetite, or perhaps di� culty sleeping at night due to irregular breathing. These are all mild symptoms of altitude sickness and pass within a day or two if you rest and cease further ascent. Keep rising and ignore your body’s warning signs, and life-threatening complications, including pulmonary or cerebral edema — the causes of countless mountaineering disasters — become very real threats.

In the construction and maintenance of mountain observatory sites, basing a core workforce at high elevation becomes unavoidable. “We have about 10 persons looking after the facilities,” says Tushar Prabhu, referring to the Indian Astronomical Observatory (4,500 metres). Four engineers, stationed at the lower elevation of Leh (3,380 metres), visit the site to maintain the photovoltaic power supply, the telescope and its instruments, and the liquid nitrogen plant, as well as look after the computer network — “but only for 2 to 3 weeks at a stretch,” he reassuringly explains. During observing sessions, however, many high-elevation observatories are now remotely operated from the comfort of lowland control rooms. The Indian Astronomical Observatory’s satellite link with its headquarters down on the steamy plains of Bangalore means that only a minimal core of hardy, multi-tasking maintenance sta� need endure the site’s thin air and bitter winter temperatures that plummet to −25°C.

Employers are all too aware that high elevation also compromises worker performance, skewing decision making and increasing the chances of accidents and costly mistakes. Michael Böcker (European Southern Observatory) reports that the attention spans and perceptual speed of sta� are among the capacities most a� ected by high elevation. Even as early as 1923 the British physiologist Joseph Barcroft noted a similar fi nding during his fi eldwork at Cerro de Pasco (4,300 metres) in Peru: “Judged by the ordinary standard of laboratory work, we were in an obviously lower category at Cerro . . . time was wasted there in trivialities and ‘bungling’ which would not occur at sea level.”

Following medical research by John B. West (University of California, San Diego) and others, some high-elevation sites are now fi tting oxygen enrichers to indoor working environments. By boosting the oxygen content in the air from its normal level of 21% to, say, 29%, confi ned work areas of the ALMA site at 5,090 metres can generate an oxygen pressure equivalent to an elevation of only 2,740 metres, which most people tolerate easily.

Elevation: The Silent Killer

Infrared astronomy from the ground is hampered by absorption by compounds in Earth’s atmosphere, particularly water vapour. The suitability of an observing site, particularly those tuning to submillimetre wavelengths, is often gauged from its Precipitable Water Vapor (PWV) value, the depth of liquid that would be obtained if all the gaseous water along the line of sight to the zenith could be condensed. PWV decreases with elevation and is sometimes less than 1 mm above the summit of Mauna Kea.

Cerro Tololo Inter-American Observatory, as seen in 2004. The largest dome is for the 4-metre Victor M. Blanco scope. DOUGLAS ISBELL AND NOAO / AURA / NSF

Evade the Water

University of Tokyo Atacama Observatory (TAO)Elevation: 5,640 m Location: Atacama Desert, Chile

Chacaltaya Astrophysical ObservatoryElevation: 17,160 ft (some gear at 17,600 ft)Location: Andes, Bolivia

James Ax Observatory – PolarbearElevation: 5,190 m Location: Atacama Desert, Chile

Atacama Cosmology Telescope (ACT)Elevation: 5,190 m Location: Atacama Desert, Chile

Shiquanhe ObservatoryElevation: 5,090 m Location: Ngari Plateau, Tibet

Chajnantor Observatory – ALMA, APEX, QUIET, et al.Elevation: 5,090 m Location: Atacama Desert, Chile

Chajnantor Observatory – ASTE, NANTEN2Elevation: 4,800 m Location: Atacama Desert, Chile

Large Millimetre Telescope Alfonso Serrano (LMT)Elevation: 4,580 m Location: Sierra Negra, Puebla, Mexico

Indian Astronomical ObservatoryElevation: 4,500 m Location: Mount Saraswati, Ladakh, India

Meyer-Womble ObservatoryElevation: 4,312 m Location: Colorado, United States

Yangbajing International Cosmic-ray ObservatoryElevation: 4,300 m Location: Yangbajain, Tibet

Mauna Kea Observatory – Keck, Subaru, IRTF, et al.Elevation: 4,190 m Location: Hawaii, United States

High-Altitude Water Cherenkov Gamma-Ray ObservatoryElevation: 4,100 m Location: Mexico

The World’s Highest-Elevation Observatories

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50 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Gary SeronikBinocular Highlight

The Alpha Persei AssociationBinocular observers tend to work with the same deep-sky catalogues as

telescope users, so it’s no surprise that the biggest and brightest Messiers and NGCs are also the best known binocular targets. Yet there are some

objects that look great through binos, but don’t appear on these popular lists. For example, consider the Alpha Persei Association, also known as Melotte 20.

Although the terms ‘star cluster’ and ‘stellar association’ are often used interchangeably, there is a subtle difference between them. Both are groups of stars that formed in the same place at the same time, but members of an association aren’t gravitationally bound to one another. Or to put it another way, a star cluster can become an association (thanks to orbital dynamics, stars in older clusters tend to drift apart), but an association won’t evolve into an open cluster.

The Alpha Persei Association lies roughly 600 light-years away, and features some two dozen stars brighter than 7th magnitude. Most of these lie between Alpha (α) and Delta (δ) Persei, the two brightest members of the group. Together, association stars fill a binocular field with plenty of sparkle. Indeed, the Alpha Persei group is one of the few objects that looks interesting only through binoculars. The unaided eye can perceive only the brightest few stars, whereas the restrictive field of view of a typical telescope excludes too many members for a satisfying view.

Because the Alpha Persei Association has so many bright stars, it’s one of the finest binocular deep-sky targets for light-polluted skies. I’ve viewed it under all kinds of sky conditions and have always enjoyed it. Not bad for an object that didn’t make the cut for the Messier or NGC lists! ✦

–1

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USING THE STAR CHARTWHENLate January 1 a.m.Early February MidnightLate February 11 p.m.Early March 10 p.m.

These are daylight saving times. Subtract one hour if daylight saving is not applicable.

HOWGo outside within an hour or so of a time listed above. Hold the map out in front of you and turn it around so the label for the direction you’re facing (such as west or northeast) is right-side up. The curved edge represents the horizon, and the stars above it on the map now match the stars in front of you in the sky. The centre of the map is the zenith, the point in the sky directly overhead.

FOR EXAMPLE: Turn the map around so the label “Facing NE” is right-side up. About halfway from there to the map’s centre is the bright star Procyon. Go out and look northeast halfway from horizontal to straight up. There’s Procyon!

NOTE: The map is plotted for 35° south latitude (for example, Sydney, Buenos Aires, Cape Town). If you’re far north of there, stars in the northern part of the sky will be higher and stars in the south lower. Far south of 35° the reverse is true.

ONLINEYou can get a sky chart customised for your location at any time atSkyandTelescope.com/skychart

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Page 51: Australian Sky & Telescope -2015

www.skyandtelescope.com.au 51

–1

Starmagnitudes

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Page 52: Australian Sky & Telescope -2015

52 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Fred SchaafTonight's Sky

Stalking the HunterOrion’s starry splendour is hard to match

When you look up, which constellation do you think is the most spectacular in the

sky? Orion, most amateur astronomers would no doubt say. But I’d go even further. In my opinion, no other constellation comes close to equaling the visual impact of Orion.

Why is that? Let me review some of the reasons Orion virtually brands our minds with its stunning starfire.

The brightness. Skywatchers often consider Orion the brightest constellation, even though Scorpius stands as winter's brightest for many observers. Mighty Scorpius does include an impressive number of stars brighter than magnitude 2.5, and an even more impressive number brighter than 3.0. But it has only one 1st-magnitude star,

Antares, which is always dimmer than Orion’s Rigel, and almost always dimmer than Orion’s variable Betelgeuse.

For those of us watching the sky from the south, you might name Centaurus and Crux as constellations that, like Orion, contain two 1st-magnitude stars. But Orion also features a remarkable supporting cast: the other five stars of its main pattern are all 2nd magnitude. Fainter stars define the less symmetrical, more rambling pattern of Centaurus. But what about Crux, with its very compact, very striking symmetrical pattern? The ‘missing’ bright star at its centre often disappoints first-time viewers. Crux’s fourth-brightest star shines at magnitude 2.8, which is relatively feeble compared to the 2.2 of

Orion’s 7th-brightest star (the faintest in Orion’s main pattern).

The pattern. The brightness of Orion’s stars is accentuated by their placement in one of the sky’s two most eye-catching patterns of stars in the mid-size range (say about 10° to 30° across). The other such pattern is not a constellation but a large asterism: the northern sky's Big Dipper. The Big Dipper has one more 2nd-magnitude star than Orion, but no 1st-magnitude star to compete with Orion’s Rigel and Betelgeuse. Additionally, the least bright star of the Big Dipper’s seven, Megrez, is a surprisingly dim magnitude 3.3.

Orion has the tremendous plus of the Belt as well. Unless we count the tiny dipper of the brightest Pleiades stars, there is no small asterism that can compare with the row of three bright stars in Orion’s Belt. I’ve written before of my amazement when I once saw first one bright star, then another almost identically bright, break into view through a tiny gap in extensive cloud cover. These were the two more easterly stars of the Belt. No such arrangement of just two stars — let alone three — could compete with this asterism for catching the eye.

Artistry beyond analysis. The symmetries associated with Orion’s form are amazing: the Belt is about halfway between Betelgeuse and Rigel, and halfway between Sirius and Aldebaran or the Hyades. It’s jauntily aslant in relation to the north-south orientation of the larger frame of Orion’s body. Like all good art, Orion’s form deviates a little from what would otherwise be a boringly perfect symmetry. And as with great art, some of what makes Orion fascinating to our eye seems to go, wondrously and beautifully, beyond all analysis.✦

Like all good art, Orion’s form deviates a little from what would otherwise be a boringly perfect symmetry.

Fred Schaaf welcomes your comments at [email protected].

The red glow of Betelgeuse marks one of the shoulders of Orion. H. DAHLE/ESO

Page 53: Australian Sky & Telescope -2015
Page 54: Australian Sky & Telescope -2015

54 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Sun, Moon and Planets Jonathan Nally

Astronomers use the term 'opposition' to describe the situation where the Sun is on

one side of the Earth while another celestial body is in the opposite direction in the sky. � e practical upshot of this is that when the Sun is setting in the west, the other object is rising in the east. And this means you have all night to observe it.

� is is what we'll have with Jupiter during February and March, as it reaches opposition on February 7. Shining at a highly respectable magnitude –2.5, the giant planet will rise at about 8.30pm (Eastern Australian Daylight Savings time; please adjust for your own time zone) at the beginning of February and get a little earlier each night, so that by the end of March it will be well above the eastern horizon by the time the sky gets dark.

A small telescope will show Jupiter's cloud bands, as well as some of its moons — the four Galilean moons at least. You can use the table on page 57 to work out when the planet's famous Great Red Spot will be visible smack, bang in the middle of its disk, which is the best time to look for it. And keep an eye out for the Moon, which will appear close to Jupiter on February 4 and March 3.

Still in the evening sky but in the west now, we have Venus and Mars. Quite low on the horizon a� er sunset, the two planets will appear to be close to each other — coming very close on February 21/22 (see the diagram at right). A very thin crescent Moon will be nearby, too. � e grouping might be a little hard to see in the twilight — a pair of binoculars will help. � e bright white of Venus will contrast well with the ruddy colour of Mars.

� e two planets will slowly separate as February runs into March. Take a look a� er sunset again on March 22 — Mars will be extremely low on the horizon, Venus will be above and to its right, and the very thin crescent Moon will in between. It'll be a very pretty sight, but I have to emphasise that Mars will be really, really low and possibly

Dynamic duoVenus and Mars are the stars of the evening show

Castor

Procyon

Pollux

Regulus

C A N I S M I N O R

G E M I N I

H Y D R A

L E O

Jupiter

Feb 1

Feb 2

Feb 3

Feb 4

Feb 5

Looking northeast

Evening, February 1–590 minutes after sunset

10º

Dusk, Feb 2145 minutes after sunset

C E T U S

P I S C E S

VenusMars

Feb 22

Feb 23

Looking west

10º

Feb 21

Jupiter and the Moon will make a pleasant pairing in the northeastern sky on the evening of February 4.

As Paul McCartney and Wings sang, "Venus and Mars are alright tonight" (sorry, Ed.), and they certainly will be on February 21, low in the western sky after sunset.

Page 55: Australian Sky & Telescope -2015

www.skyandtelescope.com.au 55

Feb 4 Full Moon Jupiter 5° north of the Moon 5 Regulus 4.0° north of the Moon 7 Jupiter at opposition 10 Spica 3° south of the Moon 12 Last Quarter Moon 13 Saturn 2° south of the Moon 17 Mercury 4° south of the Moon 19 New Moon 21 Venus 2° south of the Moon Mars 0.5° south of the Moon 25 Mercury at greatest elong: 26.7°W 26 First Quarter Moon Aldebaran 1.0° south of the Moon Neptune in conjunction with Sun

Mar 3 Jupiter 5° north of the Moon 5 Regulus 4° north of the Moon 6 Full Moon 9 Spica 3.4° south of the Moon 12 Saturn 2.3° south of the Moon 14 Last Quarter Moon 19 Mercury 5° south of the Moon 20 New Moon 21 Equinox 22 Mars 1° north of the Moon 23 Venus 3° north of the Moon 25 Aldebaran 0.9° south of the Moon 27 First Quarter Moon 30 Jupiter 5.6° north of the Moon

Times are listed in Eastern Australia Daylight Savings Time

Events Of Note

It's always a lovely sight when the Moon and one or more planets get together in the sky. Shown here is our natural satellite with Jupiter and Venus back in 2012. ESO / MAX ALEXANDER

Page 56: Australian Sky & Telescope -2015

56 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Sun, Moon and Planets

hidden in the glow of sunset. Blink and you'll miss it.

You'll have to wait a little bit longer into the evening to spot the ringed planet, Saturn. At the beginning of February it will rise after 1:00am (Eastern Australian Daylight Savings time) and slowly get earlier (about 10:00pm by the end of March) as the nights go on.

Saturn is a magnificent sight through even a small telescope, so take a look if you get the chance. On February 23, the Sun, Earth and Saturn will form a 90o angle in space, and this geometry means that the planet's shadow falls nicely over its rings, adding even more to the spectacle.

Like all the outer planets, Saturn sometimes exhibits 'retrograde motion'. This is where its normal night-by-night movement across the sky reverses, and it seems to go backwards for a while. (It's just a line of sight effect caused by Earth 'overtaking' the planet on the 'inside' lane, as it were.) Saturn will begin retrograde motion on March 15 and keep it up for about four and a half months.

Heading right back into the inner Solar System now, and this is a great time to see Mercury — in fact, between early-February and mid-March will be the best viewing time all year. The innermost planet will be visible before dawn in the eastern sky and will be quite high up, reaching 27 degrees above the horizon on February 24. Have a look for the Moon nearby on February 27. After mid-March, Mercury will begin to get lower in the sky as it begins to zip around toward the other side of the Sun. By the end of March it will be gone from the sky, only to reappear in the western sky after sunset in mid-April.

And let's not forget our own planet. On March 21, Earth reaches its autumnal equinox. If you happen to live on the equator, on this day the Sun will rise due east and set due west, and the hours of day and night will be near enough to equal.

Looking ahead to the following month, mark April 4 in your calendar — for on this night we will experience a very short total lunar eclipse. This will be the only eclipse for us this year — that's right, there will no solar eclipses visible from our part of the world in 2015. ✦

Evening, Feb 29 – Mar 490 minutes after sunset

Castor

Pollux

Regulus

G E M I N I

L E O

LY N X

Jupiter

Feb 28 Mar 1

Mar 2

Mar 3

Mar 4

Looking North-Northeast

10º

Evening, March 22–2440 minutes after sunset

A R I E S

C E T U S

E R I D A N U S

P I S C E S

TA U R U S

Venus

Mars

Mar 22

Mar 23

Mar 24

Looking West-Northwest

10º

Jupiter rides high in the night sky during March, with the almost full Moon nearby on March 3.

See if you can spot Mars low on the horizon just after sunset on March 22. The thin crescent Moon and Venus will be above and to the right.

Page 57: Australian Sky & Telescope -2015

www.skyandtelescope.com.au 57

Jupiter’s Red Spot Transit, February/March 2015 (Universal Time)

These predictions assume the Red Spot is at Jovian System II longitude 207°. If it has moved elsewhere, it will transit 1.7 minutes late for every 1° of longitude greater than 207°, or 1.7 minutes early for every 1° less than 207°. Check SkyandTelescope.com/redspot for updates.

FEBRUARY 1 6:46 16:412 2:37 12:32 22:283 8:24 18:194 4:15 14:105 0:06 10:01 19:576 5:53 15:487 1:44 11:39 21:358 7:31 17:269 3:22 13:17 23:1310 9:09 19:0411 5:00 14:5512 0:51 10:47 20:4213 6:38 16:3314 2:29 12:25 22:2015 8:16 18:1116 4:07 14:03 23:5817 9:54 19:4918 5:45 15:4119 1:36 11:32 21:2720 7:23 17:19

Moon, March 2015

PhasesFull Moon February 3, 23:09 UTLast Quarter February 12, 03:50 UTNew Moon February 18, 23:47 UTFirst Quarter February 25, 17:14 UT

DistancesApogee February 6, 06:27 UT406,154 km Perigee February 19, 07:31 UT356,991 km

PhasesFull Moon March 5, 18:06 UTLast Quarter March 13, 17:48 UTNew Moon March 20, 09:36 UTFirst Quarter March 27, 07:43 UT

DistancesApogee March 5, 07:36 UT406,385 km Perigee March 19, 19:39 UT357,583 km

N

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S

ANTONÍN RÜKL

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12 3:53 13:49 23:4413 9:40 19:3614 5:32 15:2715 1:23 11:18 21:1416 7:10 17:0517 3:01 12:57 22:5218 8:48 18:4419 4:39 14:3520 0:31 10:26 20:2221 6:18 16:1322 2:09 12:05 22:0023 7:56 17:5224 3:48 13:43 23:3925 9:35 19:3026 5:26 15:2227 1:17 11:13 21:0928 7:04 17:0029 2:56 12:51 22:4730 8:43 18:3931 4:34 14:30

Star Chartsprice $19.95A series of 18 maps (nine double-sided A4 pages) + CD covering the entire sky. � e charts have a water-resistant laminate coat to make them more durable when used outside. An additional reference guide provides an overall view of all 18 charts and an index to the constellations and major stars.

Page 58: Australian Sky & Telescope -2015

58 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Celestial Calendar

Unless a bright new comet is found in the meantime, February and March hold little promise for

comet observers using small telescopes. At the time of writing in late October, only two objects hold any prospect at all of being visible. Even these will not be easy and, from mid-southern latitudes, confined to the very start of the period.

The best prospect is C/2014 Q2 (Lovejoy), which may still be found in evening twilight low in the northwest for the first few days of February. Having

passed perihelion on January 30 at a distance of 1.29 au from the Sun, the comet is moving northward through Andromeda and will soon be lost to southern observers.

According to brightness estimates late last October, it may still be as bright as magnitude 7 as February begins, so favourably placed observers - especially those living closer toward the equator - should be able to find it using moderate-sized binoculars. Even if these brighter estimates turn out to be too optimistic, the

Last chance for Comet LovejoyDavid Seargent

David Seargent’s ebook Sungrazing Comets: Snowballs in the Furnace is available from Amazon.

C/2014 Q2 (Lovejoy) has been a very pretty comet, as shown in these images taken by Gerald Rhemann on November 27 (top) and 29, 2014.

The path of comet C/2014 Q2 (Lovejoy) during January 2015. In February it will disappear from view for southern observers, being too far north in the sky. first days of February should still find it

within range of backyard telescopes.Also low in the evening twilight,

15P/Finlay may still be as bright as magnitude 10–11 in early February according to the more optimistic forecasts. Drifting through the constellation of Pisces, it will not be an easy object, but if the optimists are right, favourably placed observers may still be able to find it before twilight claims it completely.

Page 59: Australian Sky & Telescope -2015

www.skyandtelescope.com.au 59

The American Association of Variable Star Observers has what is called its Binocular

Program - stars that can be observed throughout a complete brightening and dimming cycle with just binoculars or a small telescope. But we go further than that — in our view, observing the brighter part of a long-period variable star's cycle while missing the faint part, is still very useful. We’ve thrown in an extra-galactic challenge or two as well, and more. Not the least difference is that most of our readership and interest is in the southern sky, unlike the North Americans. They need us southerners!

In Orion, the AAVSO binocular (and naked-eye) program has only the stars Betelgeuse, W Ori, BL Ori, and BQ Ori, covered in the AS&T Nov-Dec 2011 and Feb-Mar 2013 issues, and in this issue for the latter two, respectively. Variable Stars South is hosting four finder charts for you to download, from variablestarssouth.org/ast/bqblori

BL Orionis Alan Plummer

Two Variable Targets in Orion

Star RA Dec Const Type Period Mag.BQ Ori 05h 57m 07.39s +22º 50' 20.2" Ori SRB 243 7.1 - 9.0 V

BL Ori 06h 25m 28.18s +14º 43' 19.2" Ori SRB 153.8 5.9 - 6.6 V

Finder chart for the semi-regular variable star BL Orionis, COURTESY OF THE AAVSO. North is up and the scale is approximately 15 degrees from west to east. Use charts from www.variablestarssouth.org/ast/bqblori for estimating brightness.

Included are a wider (A scale) and smaller (B scale) chart for each target. (The B scale for BL Ori is custom generated, rather than using the chart-plotting machine.)

I spend a lot of time dealing with the public on viewing nights, and I've found that carbon stars are one of the very few sights that people queuing at the eyepiece go "Ooh! Ahh!" about. One of them, BL Orionis, is a semi-regular (SR) variable carbon star with a brightness that ranges from 5.9 to 6.6, and an approximate period of 154 days. This means that an observation every two weeks is fine for this star if you want to watch its brightness slowly rise and fall.

BQ Ori is another SR variable a bit further to the north, situated virtually on the galactic equator. While you're in the area, why not check out the many nebulae and star clusters here as well? You’ll soon find you'll be looking for excuses to visit this part of the sky as often as you can.

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Betelgeuse

Page 60: Australian Sky & Telescope -2015

60 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Ross Gould Double Star Notes

Prowling through Puppis

This is the third time I've written about doubles in Puppis, a constellation with hundreds of

them accessible to mid-size amateur telescopes (say, 20- to 25-cm). Puppis is part of the gigantic, now-defunct constellation Argo Navis; in sky area Puppis is slightly larger than Orion.

We'll begin with 3rd-magnitude Pi Pup, a triple star and a useful guide star. This is a James Dunlop double, DUN 43, very wide with magnitude 3 and 8 stars, best seen at low power and showing colour contrast of orange and blue-white. It's located in a loose cluster, Cr 135; my best view was with a 10×70 finder, which showed the cluster nicely as well as Dunlop's companion to Pi.

Those with larger scopes might like to attempt HDS 1008, the bright star of Pi, found by Hipparcos in 1991 to be a very close and unequal double. At only 0.7" separation, and 3.6 magnitudes brightness difference, it will be hard to see even though the companion is bright (magnitude 6.5). A 20-cm scope would put the companion into the Rayleigh gap, but I'm inclined to think a larger scope, putting the companion outside the first diffraction ring, would be better — say, 30-cm or more. There's no new measure since 1991, though I'm expecting a new measure soon, and we don't know if this one was picked up when widening after a long period of being even closer, or if it's now closing again.

Pi Pup is quite distant, around 800 light-years, and various other stars in the cluster have similar parallaxes; so this may be one of the uncommon cases where — with HDS 1008 — we might have a genuine binary showing in a cluster; the wider Dunlop companion may be just another cluster member rather than in orbit with Pi.

Not far from Pi, about 1 degree WNW, is BU 757, with 6th- and 8th-magnitude stars some 2.5" apart. A C14 telescope (35.5-cm) at 120× showed the companion; smaller scopes might need higher powers, but 15-cm will show it. Some 20' north is a broad triple, GLI 56, with the 8th- to 10th-magnitude stars within reach of 80-mm.

Some 1½ degrees NE from Pi is HJ 3957, an easy pair with a 7th-magnitude yellow primary and 8th-magnitude companion, visible with 60-mm. Southwards from there, some 1½ degrees east of Pi, is a neat 7th-magnitude pair, HJ 3966, again easy for small scopes. The equally bright stars are neatly apart even at 50×, and cream/off-white in colour.

The doubles I 65 and I 66 are 4¼ degrees WNW From Pi. I 65 has a curious history — found by Robert Innes with a 7-inch (18-cm) refractor in 1897, it was then measured by Thomas See the following year with a 24-inch refractor at about half Innes's separation and a fairly different angle; Innes in 1900 and 1901 with the McClean 18-inch (45-cm) refractor got measures similar to See's; then a wider separation in 1902, and back to See's

Star Name Righthh mm

Declination

o '

Magnitudes Separation (arcseconds)

Position Angle(o)

Date of Measure

Spectrum

I 65 06 57.3 -35 30 6.9, 7.3 0.26" ephem 160

ephem

2015e F8IV-V

I 66 06 58.3 -35 25 AB 7.8, 9.3 1.9" 253 1991 ApSiHJ 3905 " " AC 7.8, 9.7 14.3" 270 1999DUN 38 07 04.0 -43 37 AB 5.6, 6.7 20.9" 126 1999 G3V, K0VHJ 3928 07 05.5 -34 47 6.5, 7.8 2.7" 144 2001 F2V BU 757 07 12.4 -36 33 6.0, 8.35 2.5" 069 1993 B3VPi Pup (DUN 43) 07 17.1 -37 06 2.9, 7.9 66.5" 213 2009 K3Ib, B9HDS 1008 " " 2.9, 6.5 0.7" 152 1991I 7 07 17.5 -46 59 7.1, 8.4 0.7" 203 2012 K3VHJ 3957 07 22.3 -35 55 7.1, 7.9 7.5" 191 2003 F8HJ 3966 07 24.8 -37 17 6.9, 6.9 6.9" 322 2003 F0V, F0VHWE 65 07 52.3 -34 42 5.1, 8.6 3.8" 267 2001 F5VCOO 64 07 55.6 -43 47 7.8, 11.3 5.1" 152 1999 K3IIISEE 91 07 55.8 -43 51 6.6, 6.9 0.7" 344 1996 B6V

Double star targets for small and large scopes

Hundreds of targets beckon in this southern constellation

Data from the Washington Double Star Catalogue.

1998

East

North

Apparent orbit of I 7 in Puppis

0.1

0.1

1981

2015

2049

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

2032

0.20.30.40.5 0

0

1

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www.skyandtelescope.com.au 61

separation in 1903. The many measures from 1916 to 2008 are around 0.3" or less as a consistent pattern. I 65 now has a calculated orbit of short period, 16.77 years, and a maximum separation near 0.3". So the likely explanation is that the first observation of I 65 was of another double, though I could find no likely candidates nearby. After that, nearly all the observations fit well enough for the star now identified as I 65. Given the very close orbit, observers might try with 30-cm or larger scopes. The ephemeris suggests ~0.26" separation for 2015-17, with the position angle changing from 160 to 180 (2015.0 to 2017.0).

Nearby is I 66, a simple and straightforward triple star, part of HJ 3905. The wide Herschel pair is an 1830s discovery; the Innes close pair 1890s. It presents a neat combination for 10-cm. The primary is of magnitude 7.8, with a fairly close 9th-magnitude companion at 2", and another of magnitude 9.7 at 14". The primary is white, and 150× shows the trio well.

Nearly 2 degrees ENE from I 65/66 is HJ 3928 , a little golden pair of 6th and 8th magnitude, fairly close and flanked by two fainter companions of 10th and eleventh magnitude out wide, one to each side; well seen with the 18-cm refractor at 100×.

South 9 degrees from HJ 3928 is the easy show-piece DUN 38 , both stars bright, the deep golden primary having a well separated orange companion; this is another fine object accessible to small telescopes.

From DUN 38, further south again and a little eastwards, some 10 degrees south of Pi, is our feature binary, I 7, which I briefly described in 2010. It's one of Robert Innes's early doubles found during his Sydney period in the 1890s.

Previously I mentioned a preliminary orbit by Heintz (gd 4, from 1995) with a period of 94 years. More recently, Brian Mason of the US Naval Observatory has calculated a new orbit (gd 3, 2011) with a shorter period of 85 years.

The new orbit gives a maximum separation of almost 0.9", in the early-to-mid 1990s; separation is now decreasing, and the ephemeris gives 0.68" for 2015.0, and 0.63" for 2018.0.

I 7 can be found 2½ degrees southeast of L2 [Pup], near a curved line of three brighter stars. I first observed it in 1996, around maximum separation, and the 18-cm refractor showed a deep yellow star, single at 100×, elongated at 180×,

and at 330× a close but nicely split uneven pair (the magnitudes are 7.1 and 8.4). These days, slightly tighter, it should still be a ‘figure 8’ pair with 18-cm in steady seeing, separated with larger apertures, and slightly elongated (unevenly) with 13-cm.

Closing to 0.50" by 2025.0, it will reach a minimum of less than 0.1" in 2044, then widen again to 0.5" in 2044 and 0.7" in 2055. The orbital eccentricity is very high; the big range of separation is not just a result of our line of sight to the pair. When Innes discovered it in 1894 it was approaching maximum separation.

The Hipparcos parallax gives a distance of 48 light-years, making it a fairly nearby pair. The apparent orbit (seen from Earth) has a maximum separation of 13 AU, a minimum of close to 1 AU.

The stars are main-sequence dwarfs, cooler and less massive than the Sun or the stars of Alpha Centauri. So although the period is similar to Alpha Cen's, the size of the orbit is smaller. For comparison, if I 7 were as near to us as Alpha Cen, its maximum separation would be nearly 10", less than half Alpha Cen's.

From 2nd-magnitude Zeta Pup, some 4 degrees SSW is a field with two doubles — the brighter is the close SEE 91, a Dawes-limit type double for 15-cm scopes. Last measured at 0.7" in 1996, and gradually widening from 0.4" when discovered in 1897, by 1996 when I first observed it the appearance was of elongation, not separation, of the near-equal white stars, using a 15-cm refractor at 270×. By now it might be slightly wider, but 1996 is the most recent measure at the time of writing.

In the same field, the 15-cm refractor showed COO 64 as a double at 75×, the 11th magnitude companion a little speck of light fairly close to the 8th-magnitude deep yellow primary.

And, to conclude for now — 5½ deg NNW from Zeta Pup is HWE 65. Viewed with the 18-cm refractor at 100×, it is a beautiful delicate pair, a bright 5th-magnitude pale yellowish star with B a tiny point beside it, looking dimmer than its magnitude (8.6 in this case). A fine double, and 10-cm should deal well with it. ✦

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Ross Gould has been a long-time double star observer from the suburban skies of Canberra. He can be reached at [email protected]

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62 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Sue FrenchTargets

The Fire Down BelowLacaille’s furnace glows with winter wonders.

Fornacis point toward it. Even at 17× through my 105-mm refractor, the nebula is easily spotted as an oval glow tilted north-northeast. The 11.3-magnitude central star is weakly visible, but it shows up much better at 47×, with a dimmer patch nearby. The variable star RZ Fornacis is an eye-catching, reddish-orange gem perched 16.8′ northwest of NGC 1360. It has a visual range of about 8th to 9th magnitude and a semi-regular period of 65 days. A narrowband or O III filter helps the nebula stand out better against the sky, but the central star appears faint with the former and disappears altogether with the latter. NGC 1360 is a superb sight through my 25-cm reflector at 70×. It covers roughly 6½′ × 3½′ and is brighter in its northern and western reaches.

At approximately 10,000 years old, NGC 1360 is elderly for a planetary nebula. In a 2004 Astronomical Journal paper, Daniel Goldman and colleagues argue that the nebula has an ellipsoidal shell whose density falls toward the centre, but has no sharp inner edge. The diffuse outer edge of the shell suggests that the nebula is

At the November 15, 1754 meeting of the Académie Royale des Sciences, Nicolas-

Louis de Lacaille presented a report of his scientific expedition to the Cape of Good Hope and a beautiful map of the southern skies painted by his friend Anne-Louise Le Jeuneux. Now displayed in the Paris Observatory’s Grande Galerie, this chart boasts several constellations devised by Lacaille, including Fornax, which represents a chemist’s furnace.

The Furnace burns in a part of the sky that's familiar to southern skygazers, and is even visible to many of our cousins in the Northern Hemisphere. Its treasures are assuredly worth no matter where you live.

Fornax is largely populated with galaxies, but it also holds one large, impressive planetary nebula. NGC 1360 bedecks the northeastern corner of the constellation, and the stars Alpha (α) and Beta (β)

τ3

τ6

τ7 4

α

β

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δ

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F O R N A X

RZS

f Eri

g Eri

i Eri Fornax Dwarf

1097

1187

1201

12551302

1316 = Fornax A1317

Inset shown above

1344

1350

13711385

1395

1398

1425

1360

3h 20m

–30°

3h 40m 3h 00m

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Star

mag

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4

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1336

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1351

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1381

1392

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13891427A

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χ1

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1380

1386

1399

1404

1427 F O R N A X

E R I D A N U S

3h 30m

–35°

3h 35m3h 40m

–36°

1387

Star

mag

nitu

des

6

5

78910

The author sketched the extreme barred spiral NGC 1365 as seen through her 25-cm reflector at 90×.

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www.skyandtelescope.com.au 63

starting to blend into the interstellar medium. The dim patches in NGC 1360 may indicate regions of low density or obscuring material within the nebula.

Lewis Swift described his discovery of NGC 1360 in the March 1885 issue of The Sidereal Messenger. While searching Eridanus for comets with his 4½-inch Henry Fitz refractor in 1859, he encountered a “most conspicuous nebulous star visible from this latitude.” He assumed “this wonderful object” must be well known, until he saw that it wasn’t included in John Herschel’s 1864 General Catalogue of Nebulae and Clusters of Stars.

The brightest galaxy in the northern half of Fornax is the giant barred spiral NGC 1097. It’s located 2.2° north-northwest of Beta Fornacis and due east of a 1.7°-long “dipper” of nine stars. This small grouping includes Iota1 (ι1) and Iota2 Fornacis, and attracts attention through my 9×50 finderscope.

Through my 105-mm scope at 17×, NGC 1097 is a small but easily visible oval of light, accompanied by a 5′ triangle of stars (magnitudes 8, 9, and 10) 13½′ to its south-southwest. At 47× the oval

wears an ashen fringe and a small bright centre. It’s about 4′ long and half as wide, tipped southeast. Through my 25-cm scope at 90×, the galaxy’s interacting companion, NGC 1097A, makes an appearance as a petite spot just off NGC 1097’s northwestern tip. NGC 1097 is perhaps 5½′ × 3′, with a vivid little core and subtle, starlike nucleus. The companion is much more obvious at 118×, and NGC 1097 shows spiral arms unfurling counterclockwise from each tip of the oval. NGC 1097’s core now seems slightly oval as well.

NGC 1097 is a Seyfert galaxy bearing an active nucleus whose prodigious energy output is powered by a voracious, central black hole with 100 million times the mass of our Sun. Images show that NGC 1097 is strikingly distorted by its elliptical companion. These gravitational dance partners dwell 46 million light-years away from us.

Another galaxy that reveals a spiral structure is NGC 1365, prosaically nicknamed the Great Barred Spiral Galaxy. Look for it 1.2° east-southeast of a prominent diamond of several stars,

The author sketched two Fornax Galaxy Cluster fi elds as seen through her 25-cm refl ector at 90×.

NGC 1399

NGC 1387

NGC 1404

NGC 1389

NGC 1380

NGC 1381

NGC 1379

NGC 1375

NGC 1374

including Chi1 (χ1), Chi2, and Chi3 Fornacis.

Through my 105-mm refractor at 47×, NGC 1365 is a large and modestly bright east-west glow with a fairly bright core and subtle projections at each end that give it a Z shape. The galaxy is quite beautiful through my 25-cm reflector at 90×, its graceful arms are admired more readily. From tip to tip (north-south), they span about 6′ on the sky. A magnification of 115× further enhances these fetching features.

NGC 1365 is generally thought to be a member of the Fornax Galaxy Cluster, about 60 million light-years away from us. Unlike most galaxy clusters, the Fornax group embraces many members that can be enjoyed with small telescopes.

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Page 64: Australian Sky & Telescope -2015

64 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

When viewed through my 4.5-inch tabletop reflector equipped with a wide-angle eyepiece that gives the scope a true field of 2.2° and a magnification of 35×, NGC 1365 shares the field with eight fainter Fornax Cluster galaxies. NGC 1399 is the second-brightest galaxy in the field of view. It looks roundish and about half the size of NGC 1365, with a brighter core and starlike nucleus. To the south-southeast of NGC 1399, NGC 1404 presents a somewhat smaller, round glow guarded by a

Targets

Sue French welcomes your comments at [email protected].

gold, 8th-magnitude star near its south-southeastern edge. NGC 1380 is the third-brightest resident of the field. It exhibits an oval profile whose length is about two-thirds the apparent diameter of NGC 1399, and it envelops a relatively large, brighter core and starlike nucleus.

A zigzag chain of dimmer galaxies cuts across the triangle formed by the four galaxies described above. Working our way from north to south, I see a single smudge that’s probably just NGC 1374, but it might

be the combined glow of this galaxy and its close neighbor to the south, NGC 1375. NGC 1381 is a tiny spot, perhaps elongated. Both looking like misty globes, NGC 1379 gently intensifies toward the centre, whereas NGC 1387 hosts a starlike nucleus. The final field galaxy is NGC 1386, a small oval that leans north-northeast.

I sketched NGC 1365 and two Fornax Cluster fields of view as seen through my 25-cm reflector at 90×. The sketches are all done at the same scale. NGC 1386 isn’t in either of the drawn fields, but through the 25-cm scope it’s a nicely elongated galaxy, shaped much like a double-convex lens about 2½′ long. At 118× it grows brighter toward a tiny nucleus.

Farther afield, yet still part of the Fornax Cluster, NGC 1316 is the group’s brightest galaxy. As one of the strongest sources of radio waves in our sky, it’s also known as Fornax A. If you place Chi1 Fornacis in the eastern edge of a low-power field and scan 1.3° southward, you’ll come to a 15′ right triangle of 7th- to 9th-magnitude stars, one at each corner, and a fourth along the hypotenuse. Fornax A is easily spotted to the triangle’s west.

Through the 4.5-inch reflector at 14×, NGC 1316 is little but bright, and contains a brilliant centre. At 64× the galaxy is oval northeast-southwest and sports a tiny nucleus, while a neighbour galaxy to the north now makes an appearance. NGC 1317 is fainter, considerably smaller, and only slightly oval. It harbours a brighter core and an elusive stellar nucleus. Through my 25-cm scope at 118×, NGC 1316 is about 4′ long and perhaps two-thirds as wide, with a 13th-magnitude star off its southwestern end. NGC 1317’s halo is about 1½′ across, engulfing a small, slightly oval core that runs south-southeast to north-northwest.

Fornax A’s two immense radio-emitting lobes span more than a million light-years. They’re probably the result of a galactic collision that rained material onto Fornax A’s central black hole, triggering oppositely directed jets of high-energy particles that heat the rarefied gas of intergalactic space. ✦

The giant barrel spiral galaxy NGC 1097 is distorted by the gravity of small but bright NGC 1097a. ESO

Selected Deep-Sky Objects in FornaxObject Type Mag(v) Size/Sep RA Dec.

NGC 1360 Planetary nebula 9.4 11.0′ × 7.5′ 3h 33.3m –25° 52′

NGC 1097 Spiral galaxy 9.5 9.3′ × 6.3′ 2h 46.3m –30° 16′

NGC 1365 Spiral galaxy 9.6 11.2′ × 6.5′ 3h 33.6m –36° 08′

NGC 1316 Lenticular galaxy 8.5 12.0′ × 8.5′ 3h 22.7m –37° 13′

Angular sizes and separations are from recent catalogues. Visually, an object’s size is often smaller than the catalogued value and varies according to the aperture and magnification of the viewing instrument. Right ascension and declination are for equinox 2000.0.

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66 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Exploring the Solar System Thomas A. Dobbins

An Observational MysteryWhat causes Io’s enigmatic brightening?

For telescopic observers, Jupiter’s satellite Io is hardly a showpiece object. Although 5% larger than

the Moon, Io is 2,000× more distant and, under optimal conditions, can barely be distinguished as a non-stellar disC through a 5-inch telescope. Observing Io is like observing a coin from a distance of almost 5 kilometres.

For more than a century, Io has been the subject of a number of observing conundrums — a number that is out of all proportion to its diminutive apparent size. In his popular 1954 book Guide to the Planets, Patrick Moore wrote: “Io sometimes shows peculiar fluctuations in brilliancy, and I once saw it brighten up strikingly in the space of a few hours for no apparent reason.”

In 1964 astronomers Alan Binder and Dale Cruikshank reported that observations of Io with a photoelectric photometer revealed that the satellite brightens temporarily when it emerges from Jupiter’s shadow following eclipses. This post-eclipse anomaly, which typically amounted to a 10% to 15%

increase in brightness, usually persisted for up to 20 minutes. The other Galilean satellites, Europa, Ganymede, and Callisto, never displayed this strange behaviour.

These photometric observations were very challenging because for earthbound observers, eclipses of Io occur when the satellite is less than one Jupiter radius (about 20 arcseconds) from its brilliant parent planet. Scattered light from nearby Jupiter detracts from the accuracy of the brightness measurements of Io to a greater degree than for the other Galilean satellites, whose eclipse phenomena generally occur at considerably larger angular distances from Jupiter. Nevertheless, the fact that no corresponding brightening was detected at very similar viewing geometries just before Io entered Jupiter’s shadow lent credence to the notion that the phenomenon had some basis in reality.

Cruikshank insightfully proposed that Io has a tenuous atmosphere containing an unknown gas that freezes out when Io plunges into Jupiter’s icy shadow, where it remains for just over two hours during an eclipse. He suggested that as Io re-emerges into sunlight at the end of an eclipse, frozen gas in the form of bright frost deposits blanketing the moon’s surface should reflect more sunlight briefly before sublimating or evaporating and restoring Io to its normal brightness.

Despite this plausible explanation, the phenomenon proved frustratingly sporadic and unpredictable. Observations at visible light wavelengths during the early 1970s of a dozen eclipses of Io by teams of astronomers at Mauna Kea (Hawaii) and Cerro Tololo (Chile) observatories failed to detect any anomalous post-eclipse brightenings, but in 1971 photometric measurements conducted independently at Kitt Peak and Table Mountain observatories convincingly recorded a post-eclipse brightening that was more pronounced in the near-ultraviolet region of the spectrum at wavelengths of 350 to 400 nanometres

than it was in visible light. Two years later, Cruikshank and his colleague Robert Murphy reported that they had detected Io’s post-eclipse brightening on some occasions during the previous two years but not on others.

In 1979 the twin Voyager spacecraft obtained the first high-resolution images of Io, revealing the presence of a host of volcanoes erupting with colossal violence, hurling plumes of ejecta hundreds of kilometres above an alien landscape dotted with lakes of molten sulfur and drifts of sulfur dioxide snow. The tides raised by the gravitational tug of war between the enormous mass of nearby Jupiter and the other Galilean satellites knead the interior of Io, fueling volcanic activity so intense that the surface of the satellite is continually re-surfaced with new layers of material vented by eruptions.

The sulfur dioxide gas that powers Io’s volcanoes was immediately recognised as the mystery component of Io’s atmosphere proposed by Cruikshank to account for Io’s post-eclipse brightening. The condensation and sublimation of sulfur dioxide frost provided a very convincing explanation for the fact that the phenomenon was not always observed. The amount of sulfur dioxide available would depend on the level of volcanic activity, which can vary dramatically on a time scale of days or even hours.

Although spacecraft observations all but eliminate the effects of scattered light from Jupiter, careful photometric monitoring of Io during a few eclipse events by the Voyager and Galileo spacecraft failed to detect any post-eclipse brightenings. However, during its flyby of Jupiter while en route to Saturn late in 2000, the Cassini spacecraft recorded a 15% increase in the reflectivity of Io in near-infrared wavelengths as the satellite emerged from Jupiter’s shadow, accompanied by a 25% increase in the intensity of the spectral absorption bands of sulfur dioxide frost.

Despite this confirming spacecraft observation, doubts persist that the

Of the four Galilean moons, only Io is volcanically active. Does this activity lead to its measured brightening as the satellite exits the shadow of Jupiter?

NASA / JHU / APL / SEAN

WALKER

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condensation and sublimation of sulfur dioxide is entirely responsible for post-eclipse brightening. Sulfur dioxide just doesn’t seem to be present in su� cient quantities to form frost of adequate optical thickness (several millimetres by most estimates) except in localised areas. Emissions triggered by the interaction of Jupiter’s magnetosphere and Io’s tenuous but variable atmosphere have been proposed as an explanation by more than one investigator.

Io passes behind Jupiter once during every one of its roughly 42.5-hour orbits around the planet, so eclipses are not rare by any means. � e best time to watch for these brightening events is following opposition, when the moon exits Jupiter’s shadow at an increasing distance from the planet’s limb.

In recent years, well-equipped amateur astronomers have made remarkably accurate photometric measurements of phenomena far

more delicate than the post-eclipse brightening of Io, notably the transits of extrasolar planets. Io’s post-eclipse brightening is a promising subject to monitor and study, one of those increasingly rare opportunities to solve a lingering observational mystery.

Amateur astronomer Howard Eskildsen can o� en be found observing the Sun by day and Moon by night.

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Minutes after eclipse

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Photometric measurements of Io recorded by Dale Cruikshank and Alan Binder in 1962–63 using a 16-inch telescope recorded a subtle brightening following several eclipses. Although no brightness fl uctuations were recorded before each disappearance (left), measurable brightness increases were recorded in four di� erent observations immediately following the reappearance of the moon (right).

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68 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Deep-Sky Marvels

The dark Cone Nebula crowns the Christmas Tree open star cluster. ESO

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harder to see rather than easier. Low power makes the background sky appear brighter. The cure is a nebula filter, which blocks most of the skyglow while allowing through the few specific wavelengths that many nebulae emit.

Following my friend’s advice, I screwed an O III filter onto an eyepiece that yielded 1½° of field through my 30-cm telescope, and had a look. The emission-line filter

When you walk outside and look to the northeast on these fine late summer,

early autumn evenings, the first constellation that catches your eye is mighty Orion. If you want to swing the telescope over to M42 for a quick look, be my guest. The Great Nebula is always a marvel, but tonight we’re after less familiar quarry.

Let’s begin our evening’s journey in Monoceros, the Unicorn, Orion’s neighbouring constellation to the east. A computer-controlled Go To telescope will stand you in good stead when touring this constellation for, despite its evocative name, the Unicorn is dim, with its most prominent star, Beta (β) Monocerotis, shining weakly in the backyard sky at magnitude 3.8.

If there’s a deep-sky object that spells the warmer months for me other than the Orion Nebula, it’s NGC 2237, the Rosette Nebula, an emission nebula shaped like a huge Christmas wreath that floats among the dim stars of Monoceros. I enjoyed this object for years from dark sites, but never tried to view it from my light-polluted backyard until a visiting amateur astronomer friend clued me in one cold night.

The Rosette is difficult, but it can be conquered with 20-cm and larger scopes if you remember the words ‘field’ and ‘filter.’ The nebula is large, 80' × 60', and you’ll need to put some dark space around it to provide contrast. That will require an eyepiece capable of encompassing over a degree of sky. Unfortunately, using a low-magnification, wide-field eyepiece in light pollution will make the nebula

Backyard Skydimmed the stars but brought out the nebulosity, first as disconnected patches, then as a big doughnut. The doughnut ‘hole’ is occupied by a little dipper-shaped asterism, which is part of a larger open cluster, NGC 2239, involved with the nebula.

Our Monoceros holiday theme doesn’t end with the Rosette’s wreath; there’s also a Christmas tree, NGC 2264, a lovely open cluster 5° northeast of our first stop. This ROD MOLLISE

Hopping around the

Embrace the clear nights to hunt down these deep sky delights

M1

M42M43

M78

2237-9

22642261

2174-5

G E M I N I

O R I O N

β

λ

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ιζ

V

T Betelgeuse

Rigel

2169

2232

2244

2301

M O N O C E R O S

T A U R U S

+20°

+10°

–10°

6h 30m 6h 00m 5h 30m

Star

mag

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3456

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70 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Deep-Sky Marvels

big and bright star cluster shines at magnitude 4.1 and stretches across 40' of sky. Long-exposure images of the Christmas Tree Cluster don’t do it justice, since they show hordes of background stars that obscure its shape. Through a low-power ocular, however, the triangular tree, which extends about 20' from the variable star S Monocerotis at its ‘base,’ jumps right out. This Christmas tree even has a ‘star’ at its top, the famous dark Cone Nebula, but that is a challenge for the largest scopes under the darkest skies.

Continuing in Monoceros, turn and sweep south for one degree to find a small, bright and interesting nebula, NGC 2261, also called Hubble’s Variable Nebula. At different times, this little interstellar cloud appears slightly dimmer or brighter, and its shape will change between observing sessions. That’s because

R Monocerotis, an old, evolved star within the nebula, is blowing off its outer gas layers. The interaction between the material coming from the star and the dust already in the area creates shadows that cause the reflection nebulosity to dim and brighten. NGC 2261’s variable nature impelled the famous American astronomer Edwin Hubble to do the first in-depth study of it.

Through a telescope at a magnification of 150×, Hubble’s Variable Nebula is one of the best reflection nebulae in the entire sky. This particular type of nebula, which glows by the reflected light of nearby stars rather than by its own emissions, is often faint, but not NGC 2261. It’s immediately obvious through the scope, looking remarkably like a small comet. R Monocerotis, shrouded in dust, forms the head, and the triangular 2.2' × 1.5' nebula extending

You can’t do anything about sky glow, but you can do something about ambient light. Light from nearby sources prevents your eyes from attaining as much dark adaptation as possible. Turn off any lights you can and shield your eyes. I drape a piece of dark cloth over my head when I’m at the eyepiece.

Many deep-sky observers use too little rather than too much magnification. Most objects are small to medium-sized targets, and magnifications of 100× and above will show more detail and spread out the background sky glow.

Wait for special nights. If you’re after a particularly difficult object, look for it after a weather front has passed through, when the sky is at its cleanest and driest.

Wait for special times. If you’re having trouble with a target, allow it to culminate — that is, to rise as high in the sky as it ever will. You will then be looking at it through the thinnest layer of atmosphere possible.

Wait for calm nights. Good ‘seeing’ — atmospheric steadiness — can be almost as important for faint galaxies as for planetary detail.

Nebula filters can reduce background sky glow and improve the contrast of emission and planetary nebulae. Unfortunately, they don’t work on galaxies, star clusters or reflection nebulae.

Keep trying. If you miss an object, keep after it night after night and you will often be rewarded.

Tips for Backyard Observers

A false-colour image from Kitt Peak reveals the structural complexity of the Rosette Nebula. T. A. RECTOR / UNIVERSITY OF ALASKA

ANCHORAGE, WIYN AND NOAO / AURA / NSF

Hubble’s Variable Nebula is also known as NGC 2261. NASA / THE HUBBLE HERITAGE TEAM (AURA/STSCI)

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from it makes up the tail. Remarkably, it doesn’t take a large telescope to see changes in this intriguing nebula. Even a 20-cm scope at high magni� cation is capable of detecting these variations. Dark streaks and patches can change shape over the course of just a few days.

I love nebulae and star clusters, but I � nd myself wanting galaxies. � is time of the year, with the obscuring band of the Milky Way crossing the sky, isn’t thought of as a good time for hunting galaxies. � ey are visible, however, including several in Perseus, which is low in the northwest a� er sunset at this time of the year. � e most prominent of these is NGC 1023, a member of our local galaxy supercluster.

Not only is this lenticular galaxy visible from suburban skies, on a good night it can surprise. At magnitude 9.6, it’s fairly bright for a galaxy, but its light is spread out over a relatively large area (7.6' × 2.8'), which dims it down a little. Under better conditions, NGC 1023’s large lens-shaped disk may put in an appearance. On a poor night, all you may see is the galaxy’s strongly elongated central region. But you'll have to be quick, as it sets soon a� er sunset.

Now, let’s move back southeast to mighty Orion. You’re probably aware there are other nebulae in the constellation besides M42. � e Hunter is near the Milky Way, in a star-forming region rich in gas clouds and star clusters. � e constellation is home to several famous objects, including the notoriously dim Horsehead

Nebula. Tonight, however, we’re a� er a less well known target, one few amateurs seem to know about — NGC 2174, the Monkey Head Nebula.

� is large 40' × 40' emission nebula is located away from Orion’s body in the area of the Hunter's ‘club’ in the northeastern part of the constellation. � is probably explains why it isn’t better known. It’s also not an easy object to spot. My best views of it from the suburbs have been through 25- to 30-cm telescopes equipped with nebula � lters.

At � rst, all you’ll probably see is the sparse open cluster NGC 2175 embedded in the nebula. Keep looking, however, and you may begin to make out a faint haze around the cluster’s stars. � rough my 30-cm Newtonian telescope, ‘Old Betsy,’ the nebula extends for 20', so use a wide-� eld eyepiece.

Why “Monkey Head”? In images, the nebula looks a little like the head of a simian.

Let’s continue our tour with Canis Major, the Big Dog trotting along at Orion’s heels. NGC 2362 is a bright and attractive 4.1-magnitude open star cluster spanning a mere 6' × 6'. Depending on your scope and skies, you’ll see as many as 30 stars in this small area. � at’s not the main attraction, however; it’s the bright 4.4-magnitude star Tau Canis Majoris near the centre of the cluster.

Tau makes NGC 2362 an easy � nd, and also provides an amazing ‘special e� ect.’ Stare at Tau and tap on the telescope’s tube. Naturally, the stars will jiggle, but Tau will seem to move

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The bright star Tau Canis Majoris resides smack bang in the middle of the open star cluster NGC 2362. POSS-II / CALTECH/PALOMAR OBSERVATORY

Object Const Type Mag (v) Size RA Dec

NGC 2237 Mon Emission nebula — 90' × 90' 6h 30.9m +05° 03'

NGC 2239 Mon Open cluster — 24' 6h 31.9m +04° 57'

NGC 2264 Mon Open cluster 4.1 20' 6h 41.0m +09° 54'

NGC 2261 Mon Refl ection nebula — 2' × 1' 6h 39.2m +08° 45'

NGC 1023 Per Lenticular galaxy 9.5 8.7' × 3.0' 2h 40.4m +39° 04'

NGC 2174/2175 Ori Nebula with open cluster — 40' × 30' 6h 09.7m +20° 29'

NGC 2362 CMa Open cluster 3.8 8' 7h 18.7m –24° 57'

NGC 2359 CMa Emission nebula — 10' × 5' 7h 18.5m –13° 14'

NGC 2354 CMa Open cluster 6.5 20' 7h 14.3m –25° 42'

NGC 1514 Tau Planetary nebula 10.9 2.2' × 2.0' 4h 09.3m +30° 47'

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Deep-Sky Marvels

Contributing editor Rod Mollise keeps an astronomy blog at uncle-rods.blogspot.com and is author of several books, including The Urban Astronomer’s Guide.

in a pattern different from the other stars, undoubtedly due to the contrast between it and the dimmer cluster stars. This weird effect gives Tau its nickname, ‘The Jumping Spider Star.’

NGC 2359, Thor’s Helmet, Canis Major’s premier nebula, has a reputation for being tough. That was true before nebula filters came to amateur astronomy, but this 9' × 9' cloud, like many other formerly challenging nebulae, can now be seen from the backyard. Through a filter-equipped 20-cm telescope, all I can detect is the oval body of the nebula, the helmet. With 30 cm inches of aperture, however, I can begin to see how the nebula got its name. There are two faint streamers of nebulosity extending to the west, the horns of Thor’s helmet.

Surprisingly, some deep-sky objects look better from the backyard than from under country skies. From dark sites, NGC 2354, a 6.5-magnitude, 18' × 18' open cluster that lies 11° south of Sirius, is fairly rich but nothing special. From a poorer location, however, it’s startling. With the dimmer stars gone, at 115× I see a 9.0-magnitude star surrounded by a ring of medium-bright stars. This ring, about 4' in diameter, is so perfect as to look artificial.

We’ll move northeast to the celestial Bull to complete our backyard odyssey. The sky is full of planetary nebulae, but once you leave the Messier list, most are small or dim, or both. There are exceptions, however, including Taurus’s NGC 1514, the Crystal Ball Nebula. This 10th-magnitude, 2.8'-diameter gas ball is a marvel through a medium-power eyepiece equipped with an O III filter. The Crystal Ball’s 9.4-magnitude central star is easy to see; it’s surrounded by tenuous but obvious nebulosity. Through large telescopes the nebula is elongated, but through my 30-cm it just looks round.

The night is now old and my bones are getting cold. There’s always the temptation to observe ‘just one more object’ on particularly good nights, but I’ve learned when to say when, to stop when I am still feeling good and wanting more. The beauties of the deep sky will be there waiting for me tomorrow, or next month, or next year over a lifetime of backyard nights. ✦

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Gary SeronikTelescope Workshop

This fine instrument provides an amazing 3-D effect with the Moon and planets.

Oltion’s Awesome Binoscope

Binocular telescopes are one of those ideas that sound great, yet rarely seem to work out in

practice. Everyone appreciates the rewards of astronomy with regular binoculars, so it’s easy to imagine how amazing it would be to scale up the aperture and magnification. And yet, binocular telescopes remain rare novelties. That’s because they’re not easy to make, and the difficulty runs deeper than the work involved in making twin optical tube assemblies.

But telescope-maker Jerry Oltion was up for the challenge. “I decided early on to go for simple and strong,” he says. That approach led him to ‘think inside the box.’ The optics reside in two boxes, one housing two 12.5-inch-diameter, f/4.7 primary mirrors, the other supporting dual upper-cage assemblies.

One of the most challenging aspects of a binocular telescope is coming up with a mechanism that enables you to have a range of interpupillary spacings.

Jerry’s simple and yet strong system consists of twin rotating secondary cages. As the assemblies rotate in tandem, the spacing between the focusers (and therefore, the eyepieces) changes. “I made the cages with 1/2-inch plywood rings and doorskin for the panels,” he explains.

Four sets of bolts and washers capture the bottom ring of each cage, allowing for rotation. The challenge was to precisely control that motion. But a trip to the hardware store yielded an ingenious solution. As Jerry explains, “The adjustment mechanism is a repurposed cargo-strap tightener that has a coarse-thread (8 threads per inch) screw that pulls and pushes a carriage along its length.”

Careful readers will note that the ‘gotcha’ in this scheme is the need to tweak the interpupillary spacing each time the scope is focused. But this turned out to be a minor issue. “The focusers sit between the secondary and the tertiary mirrors and move the

eyepieces sideways, so focusing does change the spacing, but not by much,” Jerry says. “I use parfocalising rings to make all my eyepieces focus within a fraction of an inch of each other, so the amount of adjustment is minimal.”

There’s no denying that building a binoscope is a lot more work than making a regular Dobsonian. Is the extra effort worth it? “In a word, absolutely,” Jerry reports. “I’d looked through other binocular scopes — up to 8-inches aperture — and knew the views could be really nice, but I wasn’t prepared for how visually arresting the images delivered by two 12.5-inch mirrors turned out to be.”

The binoscope works as well as a conventional 18-inch scope when it comes to detecting faint galaxies, but what really surprises Jerry is how it performs on solar-system targets such as the Moon. “Talk about a 3-D effect!”

I don’t know about you, but that whets my appetite for a binoscope project. For more about Jerry’s latest creation, visit www.sff.net/people/j.oltion/binoscope.htm. ✦

The spacing between eyepieces is governed by a mechanism built largely from a cargo-strap tightener purchased at a local hardware store.

Contributing Editor Gary Seronik is an experienced telescope maker and binocular observer. You can contact him via his website, www.garyseronik.com.

Jerry Oltion’s binoscope is well built and delivers awe-inspiring views. A stool and adjustable chair provide a range of observing positions. KATHY OLTION (2)

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Imaging Aesthetics

ROBERT GENDLER

The art of deep-sky astrophotography differs from most other types of picture-

making. Astro-imagers learn the fundamental techniques of combining many long exposures to suppress noise while simultaneously increasing the signal to reveal ever-fainter objects in their images. Tools such as calibration frames, pixel rejection methods, and tri-colour technique are mostly unheard of in other types of photography.

But many fundamentals of photography remain the same whether your subject is a distant galaxy or a picturesque landscape. Colour balance, contrast, and composition come into play in every great image, no matter the subject. As imagers strive to raise their work beyond the point of simple picture-taking, composition and visual aesthetics become important considerations in the journey to create a truly memorable photograph. Here are some ways to consider your next target — before opening the shutter — that can add drama and power to your compositions and set them apart from the crowd.

Zeroing in on the Focal PointIn order to push our images to that higher level, it’s important to ask ourselves the question that artists throughout history have asked themselves: What do we want the viewer to concentrate on? This is the focal point of the picture, the main subject that inevitably draws the eye and commands the most attention.

When planning a composition, I often mentally divide the picture into three components — the focal point, supportive structures, and background. These elements may be

Composing the Universe

Planning your composition can raise your imaging to a whole new level.

A little planning can often go a long way. While photographs of the Orion Nebula complex are usually presented with North at the top, rotating the composition 180° combined with the tight framing of this composition places the bright nebula at top left while other supporting structures draw the viewer’s eye around the entire image. All photos are courtesy of the author.

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obvious, such as a galaxy (the subject) surrounded by a few bright stars (supportive structures), and the background of dimmer stars in a sea of black. But they might also include less obvious divisions, particularly when shooting sprawling nebulae. We might designate the subject by increased brightness and contrast, for example, or by highly defined structures or colour emphasis.

Subtle structures in the image have importance, too, but they play a supportive role in directing the viewer’s journey to the natural focal point by way of visual or directional cues. By doing so the viewing experience becomes an orderly passage in which the elements within the image function like coordinates in a GPS, guiding the viewer in a logical and satisfying journey through the image.

Happily, most astronomical subjects have a natural focal point. Examples include the bright nuclei of galaxies or the brilliant young stars within bright nebulae such as the Trapezium within M42, the Orion Nebula. But interesting targets exist that lack a natural focal point, such as a nebulous field that stretches beyond your camera’s field of view. In this situation it becomes your task to establish the focal point through creative framing of the scene, using the supporting structures to create the illusion of a natural focal point.

The focal point doesn’t have to occupy the centre of an image. Many fine examples exist of asymmetric focal points in successful astro-images. One caveat: if the focal point is off centre, then a supporting structure needs to occupy the area opposite the focal point. This could be a smaller, more distant galaxy juxtaposed against the brighter and larger galaxy subject, or a fainter open cluster of stars. The key is to allow the main focal point dominance in the image through positioning, brightness, or selective sharpening.

Creating Visual FlowWhen viewers examine an image for the first time, they need visual cues to lead them through it, as alluded to above. This process is known as ‘flow’ — the subtle directing of a viewer’s eye through an image.

Offering engaging flow is essential because as astrophotographers we work with static subjects. We’re forced to

One challenge in astronomical image-processing is creating the perception of three dimensions in a two-dimensional image.

Above: The Trapezium star cluster in the center of M42 is the natural focal point in this photo captured by NASA’s Hubble Space Telescope. The original composition was rotated 90° clockwise so that the blue giant stars along the left side as well as the sharp bow shock at left produce a visual flow that leads to the central focal point in the image.

Below: A pleasing composition was achieved in this image of M17, the Swan Nebula, by taking advantage of the natural flow of the brighter areas of the nebula when the field is presented south-up to draw the viewer’s eye from the lower left to upper right. Often astronomical images achieve their strongest visual impact when the image is composed with the subject in mind rather than the cardinal points of the compass.

utilise the existing elements of our chosen scene while working with the variables we do have control over, including light, colour, scale, depth, and symmetry. We can use all these elements to enhance flow. Framing is also critical. Astronomical scenes often have supporting structures such as dust clouds, stars, or distant background galaxies, for example, that the photographer can frame in such a way as to create a sense of flow in an otherwise static image.

Striking a BalanceProper balance is one of the most crucial compositional elements. As a rule, pleasing balance results from appropriate contrast between the focal point, supporting structures, and the background. A group of bright stars framed along one side of an image, for example, can serve as an important directional cue, leading the eye to the focal point and helping to establish a dramatic composition.

On the other hand, while colourful star fields can be striking, if stellar intensities are too strong they can detract from an image’s focal point and supporting structures. Imagers sometimes use several tools to suppress the intensity of stars in an image, including the minimum filter and the spherise tool in Adobe Photoshop. These tools are best applied selectively and sparingly to only those stars that detract from the focal point.

Depth of FieldOne challenge in astronomical image-processing is creating the perception of three dimensions in a two-dimensional image. Often the highest praise for a stunning astrophoto is that it conveys a sense of depth and perspective.

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Imaging Aesthetics

If the focal point of an image has greater detail, colour intensity, or contrast compared with the supporting structures, the viewer is given the perception of depth. Some targets, particularly when shooting a tight close-up within a large nebula or dense star-field, may require additional processing to impose that coveted sense of depth.

Selective sharpening of key areas in an image full of bright and dark nebulae can often add a vivid sense of depth to an image. To enable the viewer’s eye to zero in on the subject quickly, you can leave regions within your photo “softer” than the area you’ve designated as the focal point. A similar approach works well when imaging galaxy clusters or star clouds within the Milky Way.

Complementary ColoursColour composition can also be integral to the success of an astrophoto. When shot in natural colour, astronomical objects tend to display a limited palette of blues, reds, yellows, and blacks. A glance at a colour wheel will reveal that certain colours have greater appeal when they appear opposite their complementary colour. The bluish reflection nebulae that often appear adjacent to reddish emission nebulosity within the plane of the Milky Way, for instance, can contribute

to a pleasing composition. Knowing the hues of objects in advance can often help you to create stimulating colour contrast.

Astrophotographers working with narrowband filters have more leeway to take advantage of complementary colour schemes, because they can assign each narrowband image to a different colour channel to achieve dramatically different results than imagers working in RGB colour.

The original landscape framing (left) of the star-forming region NGC 6188 in Ara lacks drama. Rotating the composition 90° counterclockwise and cropping to a square format creates a more appealing scene with a clear focal point that takes advantage of the natural axis of the dominant structures in the image.

This mosaic was composed using the ‘rule of thirds’ by positioning NGC 2070 at the intersection point of a grid dividing the image into 9 sections. Smaller nebulae serving as supporting structures throughout the field help to balance the composition.

Format DecisionsOne of the simplest but most important processing decisions is how to manage the aspect ratio of your image. Should you present the image in landscape or portrait mode, or as a square? This choice can have profound effects on the visual impact of an image.

You’ll want to ask yourself: what is the dominant axis of the structures in the image? If objects tend to run along the horizontal axis, then a landscape

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format will likely be in harmony with those structures and offer a more appealing viewing experience. A composition with mostly vertical structures will benefit most from a portrait composition. And fields in which the long axis runs diagonally or targets a well-centred, round focal point will likely present best in either square or nearly square format. Whatever orientation you choose, try not to fight the natural dominant axis of the object.

When I complete an image, I often experiment liberally with cropping — shrinking a field of view around a small galaxy, say, or getting rid of distracting secondary structures — as well as rotating the image to find the most appealing presentation. In astronomical imaging, one cannot change his or her viewpoint to the object, but managing the scene by way of framing, cropping, and rotating can produce some spectacular results.

Rules, Rules, RulesIn traditional photography the well-known rule of thirds and its variations are helpful guidelines for composing a picture. The rule of thirds suggests that when planning a composition, the photographer should divide the image into a grid of nine equal parts by mentally placing two equally spaced horizontal and vertical lines over the field. The photographer should then position salient compositional elements at the four points of intersection.

This compositional strategy produces a visual storyline with energy, direction, and flow accentuated by a more intriguing off-centred focal point. Significant structures need not fall precisely on the points of intersection to take advantage of this rule. Astronomical objects that benefit most from the rule of thirds are C- or U-shaped nebulae, galaxy clusters, and complex star-forming regions with juxtaposed star clusters and nebulae.

Composing PanoramasOne of the most daunting tasks in astrophotography is producing effective wide-field panoramas. By their nature they are exclusively mosaics, so you have greater opportunities to plan the composition and position key objects and focal points in advance.

Because of the extreme aspect ratio of panoramas, they often require some deviation from the standard

compositional rules. The rule of thirds or a single focal point — mainstays for non-panoramic images — do not always work with positioning vital objects and structures within an astronomical panorama. You might position key objects or main focal points of the vista within the center third of the image, for instance, with supporting structures and background elements filling the outer thirds.

In sum, composing astronomical scenes can be challenging due to the

limitations of photographing static celestial objects from our fixed viewpoint. But taking time to carefully plan the composition before beginning the first exposure can make the difference between an adequate image and a timeless treasure.

Top: In this image of NGC 5033, the long axis of the galaxy is composed as a vertical axis, which robs this horizontal composition of any tension. Above: By rotating the image 45° counterclockwise and cropping to a nearly square format, the axes of the galaxy, along with the bright star at bottom left, engage viewers by allowing them to read the image along the natural flow beginning at the lower left.

Learn more imaging techniques in author Robert Gendler’s latest book Lessons from the Masters: Current Concepts in Astronomical Image Processing, from which this article was adapted.

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Astrobiology

A Universe ofDarkOceans

The icy bodies of the outer Solar System might be teeming with life

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CALEB SCHARF

There aren’t many fields like astrobiology. In the past I’ve even heard it called the science

without anything to study. But the future has always been its strength; success in astrobiology would revolutionise our perspective on the nature of the cosmos, making Copernicus’ decentralisation of Earth seem like a prehistoric rite of passage.

A critical task for astrobiology is not just finding life elsewhere, it’s finding life that’s truly independent of terrestrial life. For example, if we find extant or extinct organisms on Mars, there’s a good chance they’ll be related to life on Earth — part of a genetic diaspora from microbe-laden planetary material thrown around the Solar System by 4 billion years of asteroid impacts. Either the Martians will be Earthlings or the Earthlings will be Martians. This remarkable discovery still would not help us determine the rate at which life emerges across the universe and the nature of its origins.

This is one reason why it’s so important to use spectroscopy to measure chemical biosignatures in exoplanet atmospheres. But is there a chance to study in detail a truly separate strand of life much closer to home? There could be, deep within some of our most alien neighbours.

Dark, Fluid RealmsThe icy moons of Jupiter and Saturn represent just the tip of the proverbial iceberg. Europa is the poster child. Its surface is frozen water at temperatures ranging from 50 to 110 Kelvin, with minimal cratering, suggesting an age of barely 50 million years. It’s also crisscrossed by a tapestry of geographic features. Shallow ripples and cracks stretch for hundreds or even thousands of kilometres. Images from the Galileo spacecraft revealed plate-like zones and highly jumbled areas, and curious blushes of brownish reds and oranges. Galileo even detected an induced magnetic field around Europa, a clear signature of a conductive interior layer

reacting to Jupiter’s intense electromagnetic environment.

In late 2013, a team led by Lorenz Roth (Southwest Research Institute) announced that it had pushed the Hubble Space Telescope’s STIS instrument to its limits and discovered a remarkable plume of water vapour emanating from Europa’s southern polar region. It’s a very tricky observation, but there seems little doubt that when the moon is at the far point in its elliptical orbit, it spews water into space. All evidence points to Europa having a global ocean of liquid water hidden below its icy crust.

And Europa is not alone. Its Jovian neighbour Ganymede also likely harbours deep liquid water, perhaps in multiple layers. At Saturn, geyser-spouting Enceladus — just 504 kilometres across — may contain a subsurface sea in its southern polar region. Titan, with its thick atmosphere and seas of liquid hydrocarbons, is also a prime candidate for a deeper layer containing a vast water-dominated ocean. And trans-Neptunian bodies such as Pluto and Eris likely host their own dark, fluid realms.

What produces and maintains these oceans? Europa has an iron centre surrounded by a thick rock core, with its water layer on the outside. The heat of its initial formation has largely dissipated, but billions of years later the internal temperature is maintained by the radioactive decay of uranium, thorium and potassium in the rock. In this way, Europa’s warm core drives close to 200 gigawatts of power into the water’s base — raising temperatures to around 250 Kelvin.

Like volcanically active Io, Europa also revolves around Jupiter in a mildly elliptical orbit — maintained by the pull of the other Galilean satellites. Changing gravitational-field gradients, or tides, work these moons like pieces of putty, and friction generates additional heat. For Europa, these forces may also generate internal, resonating Rossby waves that carry a

THE GEYSERS OF ENCELADUS Artist Walter Myers portrays the powerful geysers erupting from the south polar region of Saturn’s small moon Enceladus. The geysers contain water, salts and hydrocarbons, strongly suggesting an ocean not far beneath the surface.

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Astrobiology

thousand times the energy of frictional dissipation. Altogether, tides pump at least a trillion watts of additional power into this moon, raising the internal temperatures to the levels needed for liquid water. In places such as the Pluto-Charon system, a history of tidal exchange and evolution could similarly promote the formation of an internal ocean.

Critically, a dose of ammonia and other compounds significantly increases the range of pressures and temperatures where dark oceans can occur. For example, add 30% ammonia by mass to a body of water and it’ll freeze at around 175 Kelvin instead of 273 Kelvin (depending on the pressure), greatly reducing the energy budget needed to keep a subsurface ocean in its liquid state.

In 2013 astronomers Mike Brown (Caltech) and Kevin Hand (JPL) published Keck spectroscopic data of Europa with 40 times the resolution of Galileo’s instruments. On Europa’s trailing face (the side permanently downwind of the orbital motion), they discovered a coating of magnesium sulfate, along with sodium and potassium sulfates. The sulfur comes from Io’s volcanoes, spewed into a torus of plasma surrounding Jupiter, and transferred to Europa. But the magnesium, sodium and potassium once resided in a salty internal ocean — a briny mix that would taste (yes, literally) a lot like Earth’s oceans. Enceladus’s plumes include sodium salts and small amounts of methane, carbon dioxide, ammonia and acetylene. And other icy bodies show

CRACKED ICY CRUST NASA’s Galileo orbiter returned this enhanced-colour image of Europa’s Conamara Chaos region. The broken cracks and ice blocks strongly suggest a constantly shifting crust akin to plate tectonics on Earth, indicating that the surface ice is overlying a water ocean. Spectra have revealed salts and organics on the surface, an encouraging sign for life. NASA / JPL / UNIVERSITY OF ARIZONA

BENEATH THE ICE This illustration depicts an ocean lurking not far below Europa’s icy surface. Observations suggest that chloride salts from this ocean rise up through cracks and eventually make their way to the surface. Io and Jupiter are depicted in the background. NASA / JPL-CALTECH

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surface evidence for impure water.To better understand the

configuration of dark oceans, researchers have built virtual planetary worlds that balance gravity, pressure and internal heat to mimic conditions inside these icy bodies. Ganymede may be like a multilayered cake of different phases of ice and liquid. Titan may have a complex ocean that resides between a layer of water-dominated ice with its outermost hydrocarbon crust, and a deeper high-pressure water-ice zone. Recent Cassini spacecraft data, including measurement of 10-metre tidal deformations and gravity variations, indicate that Titan’s outer shell consists of icy material floating above a highly salty inner ocean. The ocean may decouple Titan’s entire surface from the spin of its core — an extraordinary phenomenon seen in Cassini’s Doppler ranging, where surface features have appeared to drift in their expected location over the years, not moving in synch with the moon’s expected rotation.

The potential capacity of dark oceans in our Solar System is astonishing. Adding up the estimates for known satellites yields a volume that could be sixteen times that of all Earth’s oceans. And if we also consider trans-Neptunian worlds, then radiogenic heating, tides from moons, plus insulating outer shells of frozen water,

methane and nitrogen, could create a total dark ocean volume more than that of all other liquid water in the Solar System.

Splendid IsolationShortly after the Voyager 1 flyby in 1979, scientists realised that Europa’s interior could harbour life. Not only is liquid water a critical agent in all known biochemistry, oceanographers had also begun finding complex ecosystems in the abyssal depths of Earth’s oceans. Rich communities of chemosynthetic microbial life cluster around hydrothermal vents at mid-ocean ridges — living directly off the vents’ mineral-rich spoils. These in turn support a startling number of tubeworms, shrimp, snails, crabs and many other species. At ocean depths extending to more than four kilometres, where water pressure reaches hundreds of atmospheres, these organisms never see sunlight. They’re entirely powered by the planet’s geophysical and geochemical energy. A dark ocean benearth the surface of a distant world might offer an analogous habitat. If we find living organisms at Europa or Enceladus, then life in general could inhabit a vast swathe of the outer Solar System.

But would life in these places be truly independent and isolated? Careful simulation of the

interplanetary dispersal of impact-ejected material suggests the answer is yes. Barely 1 in 10 million pieces of Earth or Mars material ends up impacting outer worlds such as Europa. The deep Jovian gravity well also means that any crumbs that make it to Europa will impact its surface faster than 70,000 kilometres per hour (20 km/second) — more than enough to vaporise a rock and its contents into constituent atoms — an exceedingly efficient sterilisation process.

On Europa’s trailing orbital face, high-energy electrons also dump well over 100 rad of radiation per second — enough to give an exposed human a lethal dose in about 10 seconds. Even the hardiest, most radiation-resistant organisms on Earth will have their DNA denatured and broken up by this onslaught.

That radiation is bad news for human explorers, but good news for the deep ocean’s biological isolation and

BURSTING AT THE SEAMS Above: This Cassini image shows geysers shooting water-ice particles dozens of kilometres into space from Enceladus’s south polar region.

ENIGMATIC ENCELADUS Left: NASA’s Cassini orbiter returned this portrait of Enceladus. The moon is at or near the top of the list of potential abodes for extraterrestrial life. The geysers have been imaged near the south pole, around the region of the ‘tiger stripes.’

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If we find living organisms at Europa or Enceladus, then life in general could inhabit a vast swathe of the outer Solar System.

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Astrobiology

chemistry. An ocean without oxygen might be a tough place for anything but the simplest and most slow-living organisms. But this same intense radiation at Europa’s surface should generate a plethora of oxidants, including hydrogen peroxide and other compounds. Mixing these into the liquid interior can help drive the chemistry of a more complex biosphere.

Recently we’ve discovered more examples of terrestrial life forms that exhibit extraordinary survival skills suited to lonely conditions devoid of resources. For example, in 2008 scientists found a species of bacteria — Desulforudis audaxviator (or bold traveller, a� er a quote in Jules Verne’s Journey to the Centre of the Earth) — eking out an existence in water pockets that have been isolated for millions of years some 2.8 kilometres down in the rock of a South African gold mine. � is single-celled organism not only exists in splendid isolation, it e� ectively lives o� radioactive decay and rocks. When particle radiation from uranium and thorium in the surrounding environment splits water molecules, it produces free hydrogen for the bacterium to breathe, and sulfate compounds for consumption.

� is remarkable biochemical trick doesn’t prove that D. audaxviator started out in these water pockets, since its genetic makeup still comes from the same ancestral stock as the rest of Earth life. But some scientists have proposed that terrestrial life originated around hydrothermal vents or other parts of a deep biosphere — an option that would bode well for life starting up in dark oceans elsewhere.

Accessing the OceansStudying icy worlds and their watery depths in-situ is a tricky business though. In 2022 ESA hopes to launch its JUpiter ICy moons Explorer (JUICE), targeting Ganymede, Europa and Callisto — particularly Ganymede, the only moon with a magnetic � eld. NASA’s Europa Clipper is still at a concept stage for a 2025 launch; it would make at least 32 � ybys of Europa, mapping it and applying an ice-penetrating radar, as well as trying to � y through and sample the water plume. Both missions are multi-billion-dollar a� airs that will have to contend with hardware-damaging particle radiation and Jupiter’s deep gravity well.

DARK EARTH ECOSYSTEMS Left: Single-celled bacteria belonging to the species Desulforudis audaxviator survive more than a kilometre below Earth’s surface in the complete absence of sunlight, oxygen and organic compounds. The species has survived for millions of years by feeding on chemical food sources in the surrounding rock. Right: In the late 1970s, scientists discovered that the energy and minerals pouring out of hydrothermal vents on the ocean fl oor can sustain a wide variety of life forms despite a complete lack of sunlight. This image shows tubeworms surrounding a ‘black smoker.’

WIK

IPE

DIA

NO

AA

EUROPA GANYMEDE ENCELADUS

TITAN

MOON INTERIORS These cutaway diagrams depict scientists’ best current understanding of the interior structure of four moons of the outer Solar System. All four exhibit strong evidence for liquid layers below their icy surfaces. Future missions might someday reveal whether these worlds harbour life. S&T: GREGG DINDERMAN

Ocean

Ice layersOcean layers

Icy shellOcean

Icy shellOcean

Putative Oceans ComparedObject Mean Ocean Crust Thickness Ocean Volume Thickness (km) Above Ocean (km) (billions of cubic km)

Earth 4 — 1.3

Europa 90 70 2.3

Ganymede 800 total Multilayer > 1.0

Enceladus 10 40 0.000012

Titan 230 200 14.5

Triton 160 170 2.4

Pluto 150 210 1.5

Eris 200 180 2.6

Moon sizes not to scale.

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Caleb Scharf is an astrophysicist and the Director of Astrobiology at Columbia University in New York. His latest book is � e Copernicus Complex: Our Cosmic Signi� cance in a Universe of Planets and Probabilities. He also authored Extrasolar Planets and Astrobiology and Gravity’s Engines.

A N T A R C T I C A

SouthPole

LakeWhillans

R o s sS e a

W e d d e l lS e a

McMurdoStation

A Subsurface Antarctic Lake Teeming with LifeLike the icy worlds of the outer Solar System, Antarctica also has isolated subsurface bodies of liquid water completely cut o� from sunlight. Since these lakes were fi rst identifi ed in the 1990s, scientists wondered if they harbored life. As reported in the August 21 issue of Nature, the answer is a defi nite yes.

After careful preparations to avoid contamination, an international, multidisciplinary team including Brent Christner (Louisiana State University) and John Priscu (Montana State University) used a hot-water drill to bore down into Lake Whillans, a small body of water about 800 metres below the surface. The team brought up 30 litres of water. Early analysis reveals 130,000 living cells per millilitre of lake water, a density roughly equivalent to that of deep oceans. Amazingly, the team has identifi ed at least 3,931 distinct species of bacteria and archaea, meaning this cold, dark, nutrient-starved body supports a teeming ecosystem of life forms. Many of the species are related to previously known marine microbes that derive energy by breaking down minerals in rocks and sediment.

“The subglacial lake we studied is very di� erent than the sub-ice oceans that presumably exist on the ice moons,” says Christner. “But studies like ours have expanded the known boundaries of life on Earth, which are the conditions used to extrapolate the likelihood of life surviving elsewhere.” — Robert Naeye

NASA EARTH OBSERVATORY

But aside from perhaps testing the contents of geysers, these missions won’t venture into a dark ocean itself. For that we’ll have to wait for ideas that are barely o� the drawing board: mole-like burrowing thermal drills and ‘inchworm’ robots to penetrate rock-like crusts of water — perhaps lobbed into the same cracks that are venting water into space. � ese concepts are being tested in relatively benign polar ice here on Earth, as engineers learn what it takes to operate in such extreme conditions.

� is same technology could also be applied to descend into trans-Neptunian worlds such as Pluto or Eris. Despite their distance (and even lower surface temperatures), without the intense radiation environment around Jupiter to damage hardware, these worlds might be equally attractive biologically isolated targets. Much like Europa, surface features and compositions can provide clues to the interiors. When NASA’s New Horizons buzzes Pluto in July 2015, we’ll perhaps learn more about its putative interior ocean.

� e challenge to exploring such places is paralleled by the hurdle of acknowledging that stellar radiation may not be the only way to power living environments across the universe. Radiogenic heating and latent heat of formation represent key components of this energy budget, but tidal dissipation may be a critical factor in the long term. And that’s where things get interesting, because tides are common, and are linked to the fundamental structures of planetary systems.

� e tidal power warming Europa’s interior is ultimately being drained from Jupiter’s angular momentum, a � ywheel carrying about 1033 joules. � at’s about the same as the total energy of photons emitted by the Sun in 100 days, or by a low-mass M-dwarf star in a couple of centuries. But Europa’s drain is unlikely to ever exceed 1013 joules per second (ten trillion watts worth of power), so in principle Jupiter’s angular momentum could power a dark ocean for at least a trillion years — far outlasting the Sun’s main-sequence lifetime. � is is contingent on other factors, such as

maintaining the mean-motion orbital resonance between the Galilean moons, and whether or not any icy moon survives the aging Sun’s in� ated luminosity 5 billion years hence.

But if dark oceans exist in our Solar System, they must exist across the cosmos. � e enormous diversity of planetary-system architectures can give rise to all manner of situations where icy bodies are tidally � exed and warmed. If life can get started in Europa or Enceladus, it can surely get started in similar environments. Our galaxy could be full of isolated ecosystems inside icy moons and planets, many of which are kept liquid by radioactive isotopes, and tidal friction driven by nothing more than orbits and spins — truly the children of celestial mechanics.

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84 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Public Astronomy

A visionary project to build a third telescope dome at Sydney Observatory is almost

complete. Funded by the NSW Department of Family and Community Services, Ageing, Disability and Home Care and the Museum of Applied Arts and Sciences (MAAS), and approved by the NSW Department of Heritage, it will provide access for all to astronomical telescopes to view the stars and planets. � e project’s particular target audience is people living with disabilities and their carers, which means that accessibility is core to every part of the project.

� e project sees a return to Sydney Observatory of a historic metal dome and a spectacular astrographic telescope removed from the site in 1986. � e Melbourne astrograph, designed by Sir Howard Grubb & Sons in Dublin for the Astrographic Catalogue and Carte du Ciel ('chart of the sky') projects, was delivered to Melbourne Observatory in 1890. In 1948 it was purchased by the NSW Government Astronomer, Harley Wood, for Sydney Observatory to use to complete the Melbourne and Sydney zones of the Astrographic Catalogue, as recommended by the International Astronomical Union.

� e Astrographic Catalogue and Carte du Ciel were projects to photograph and catalogue the entire celestial sphere, stimulated by the revolution in astronomy caused by the application of photography in the mid-19th century. When the project was initiated in 1887, there were numerous observatories in the Northern Hemisphere, but Sydney and Melbourne observatories were two of only a small number of well-established observatories in the Southern Hemisphere able to do the work. By 1900 Perth Observatory had enthusiastically joined in. Pietro Baracchi, who succeeded Robert Ellery

as Government Astronomer of Victoria, wrote to William Ernest Cooke, Government Astronomer of Western Australia:

‘I fully expected you would be allotted a zone of the astrophotographic work and I am glad of it. Australia will thus contribute about 1/7th part of the whole undertaking which is extremely creditable to the colonies.’ (Baracchi, 7 October 1898)

With assistance from Adelaide Observatory, which provided reference stars, the three Australian

observatories photographed and measured a large proportion of the night sky. As it turned out the Sydney zone was one of the richest sections of the sky because it included a large section of the Milky Way near the Southern Cross.

From 1964 the telescope was used to take photographs for the Southern Sydney Star Catalogue and, when the Observatory ceased astronomical research, amateur astronomers used it to photograph comets and other celestial objects, including Comet

Open SkiesSydney Observatory's new dome and telescope o� er access for all

as Government Astronomer of

The restored dome being lowered onto the new building at

Sydney Observatory.T. STEVENSON

Harley Wood using the

astrograph in 1952. SMH

/ MAAS SYDNEY

OBSERVATORY

BY TONER STEVENSON

Mary Allen and Ethel Willcocks, who were employed to measure star positions on the glass plate photographs taken with the astrograph, seen at work in 1941. PIX / MAAS SYDNEY OBSERVATORY

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Halley. In 1986 the telescope was transported to Macquarie University and stored until 2008.

Over the past 12 months, MAAS conservators Tim Morris and Carey Ward, with the assistance of expert volunteers, have restored the telescope. By the time you read this, the building will be complete, the telescope tubes will have been installed, and the lenses and photographic apparatus will be attached.

� e Astrographic Catalogue was also important socially in that it introduced women into astronomy, at a time when there were few paid positions in the newly federated colonies open to women, except as domestics or barmaids. A signi� cant number of educated women were employed as astrographic measurers

and computers at Sydney Observatory. � e new building will house an exhibition that tells this story and features a measuring machine used from 1916 by the � rst NSW star measurers, Ida Digby and Irene McDonald.

During construction there have been many major events when my excitement was hard to contain. One of these was the delivery of the mount for the astrographic telescope; the other was the delivery and installation of the dome.

� e heritage dome was originally constructed by local company, Morts Dock Engineering in 1951, under instruction from NSW Government Astronomer, Harley Wood. In 1986 it was sent to Macquarie University where it sat in a � eld for over 20 years. � e university had originally planned to use it as part of its own observatory in which the telescope would be used for further research. Nick Lomb, then curator of astronomy at Sydney Observatory, worked closely with Macquarie's Professor Alan Vaughan to ensure the instruments, dome, photographic negatives and associated log books were all preserved.

� e copper amalgam dome has been restored by the NSW Government Architect’s O� ce, and on November 6, 2014, it was craned onto the new building in the presence of various dignitaries including the Minister for the Arts and Deputy Premier, Troy Grant; Minister for Disability and

The restored Melbourne astrograph in the MAAS Conservation workshop, ready to be installed in the new building. MAAS

The DFM workshop in Colorado showing the new telescope being built for Sydney Observatory. K. MELSHEIMER / DFM

A cut-away artist's impression of the new building, showing the astrograph on display and the new telescope in the dome. The building will feature disabled access and a special eyepiece on the dome that facilities easy viewing. NSW GOVERNMENT ARCHITECTS

Ageing, John Akara; MAAS Director, Rose Hiscock; and Jim Longley, Chief Executive of Ageing Disability and Home Care, NSW Department of Family and Community Services. � e dome now sits atop a new cylindrical building, constructed of rendered brick, metal and glass, with a metal pier separated from the building to isolate the telescope from vibration.

� e original concept for the building was developed by the NSW Government Architect’s O� ce. It is located on the eastern side of the entry to Sydney Observatory, in the same location where the astrographic buildings of the nineteenth and twentieth century stood. To ful� ll its main purpose of providing an accessible telescope experience, the structure includes a li� right up into the dome.

Selecting the best telescope for the public to use was a major piece of work for Geo� Wyatt, education program o� cer, and Andrew Jacob, curator of astronomy. Comparisons were made between many available instruments, to � nd the one that would give the best viewing from a city environment. Andrew James, well respected amateur astronomer and astronomy history expert, advised on the selection, as well as its placement in the dome from the viewpoint of a wheelchair user.

� e � nal decision was to purchase a telescope from a company in Colorado, USA, called DFM Engineering, which has a unique design for a purpose-built attachment, called an Articulated Relay Eyepiece. � is extended eyepiece enables a person in a wheelchair to use the telescope by moving the eyepiece closer to them, rather than trying to get the person in the wheelchair into a viewing position. It is unique to DFM Engineering.

� e project is part of a larger master plan to increase access to astronomy and bring Sydney Observatory’s collection home. It is a major enhancement of access to the Sydney Observatory site, and will provide a � rst-class astronomical experience for all visitors.

Toner Stevenson is Manager Sydney Observatory, MAAS. She is a Doctoral Candidate at � e University of Sydney where she is completing her thesis about the involvement of women in the Astrographic Catalogue in Australia.

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86 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

AS & T Test Report Rod Mollise

As Robert Heinlein used to say. “There ain’t no such thing as a free lunch.” That’s usually true, but I

almost feel like I got a free meal with Celestron’s Edge 800 Schmidt-Cassegrain Telescope and VX mount. I found the combination of the advanced 20-cm SCT and inexpensive German equatorial mount (GEM) surprisingly capable, especially

An ensemble of Celestron equipment provides excellent visual and photographic performance.

WHAT WE LIKE:

● Excellent Go To accuracy● Tracking good enough for unguided 30-second exposures● Stable with an 8-inch SCT and accessories

WHAT WE DON’T LIKE:

● Hand-control cable is too short● The included counterweight is too light for use with the telescope and heavy cameras or accessories

Celestron Package:

A Lot for a Little

VX Mount

The author’s Celestron 20-cm Edge SCT sits atop a VX German equatorial mount. The standard 9x50-mm finderscope is attached. A 5-kg counterweight is included in the package. ALL PHOTOS COURTESY OF THE AUTHOR

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when equipped with Celestron’s Edge f/7 reducer, o� -axis guider, and StarSense auto-alignment system.

I have dreamed of an enormous SCT on a fork mount to ease me into my golden years. Unfortunately, I have to carry my scope to dark sites to do my best observing, and I really didn’t want to haul a 35- or 40-cm telescope around. � e more I thought about it, the more convinced I became that an 20-cm SCT was still the scope for me. Maybe my retirement scope should be a C8 of a new type, though, Celestron’s Edge 800.

Di� erent from other Schmidt-Cassegrains, the Edge includes a built-in corrector-lens system that both � attens the SCT’s normally curved � eld and reduces coma, the blurring of stars at the � eld edge. � e Edge 800 is a scaled-down version of its innovative big sister, the Edge 1400.

I thought I’d purchase a new mount too — one that Celestron is pairing with the Edge 800, the Advanced VX. � e VX’s payload capacity is 14 kilograms, making it the company’s smallest computer-equipped GEM. But it’s well matched for a C8.

I purchased the telescope and mount last year, and they arrived in pristine condition. � e tube came equipped with a 50-mm � nder and a Vixen-format dovetail bar to � t the VX. AS&T recently borrowed a StarSense and an o� -axis guider from Celestron and shipped them to me to complete the package so I could write this review.

� e box that contained the VX mount included the GEM head, a 5-cm steel-legged tripod, a single 5-kg counterweight, the NexStar Plus computer hand control, a cable for updating the mount’s � rmware, an instruction manual, the basic version of So� ware Bisque’s � eSkyX planetarium so� ware, and a DC power cord with a cigarette-lighter-style plug.

� e Edge 800 is a striking pale green and the mount is impressively well � nished for a GEM in this price class. I particularly appreciated the VX’s large adjustment knobs, well-laid-out control panel, and big power switch that’s easy to manipulate with gloved hands.

Visual UseOn my � rst clear night, I hustled

the new scope out to my club’s dark site. I didn’t run into any problems assembling the mount or attaching it to the scope. A� er a little practice, most people won’t need more than 10 to 15 minutes to set up the Edge/VX combo for visual use.

� e big deal, though, was not how easy the scope and mount were to assemble, but how easy they were to transport. � e package breaks down into easily manageable components that encourage me to use it frequently. At 6.4 kilograms for the telescope, 7.7 kilograms for the mount head, and 8.2 kilograms for the tripod, I never had to strain. � e telescope was quite stable on the mount with vibrations dying out in a couple of seconds.

Before the VX can locate objects, it must be Go To aligned. � e � rst step is entering the time, date, time

metre-long hand-control cable, which is a bit short.

The Edge f/7 Reducer� e addition of Celestron’s Edge focal reducer converts the f/10, 2,000-mm-focal-length Edge 800 to an f/7, 1,400-mm-focal-length telescope that delivers lower powers and wider � elds of view. � e reducer is speci� cally designed to work with the Edge’s built-in corrective lenses to preserve the scope’s � at � eld. Although intended for astrophotography, I found the reducer very e� ective for visual use as well.

For prime-focus deep-sky imaging, a focal reducer is highly desirable. � e Edge reducer, which is optimised for small imaging chips, almost doubles the size of a telescope’s � eld and cuts required exposure times in half. With my Canon DSLR, stars were sharp all across the frame.

Unguided ImagingSince astrophotography was in my plan on a recent � eld trip, I kept things simple. I shot through the SCT and reducer with my DSLR, but I didn’t

A DSLR is attached to the Celestron o� -axis guider. The auto-guider camera is not part of the reviewed Celestron package.

WHAT WE LIKE:

� Sharp stars to the field edge

WHAT WE DON’T LIKE:

� Using larger imaging chips could pose a problem

Edge Focal Reducer

Even at 100×,anything I requested from horizon to horizon was in the eyepiece when the mount stopped.

zone, daylight-savings time status, and location into the hand control. Most of these entries will be a one-time job because the mount is equipped with a battery-powered, real-time clock that keeps the date and time current.

� ere are several alignment options, but the most accurate is the two-star alignment. When you select that option, the VX will point at two stars it chooses from its database. A� er you centre them in the � nder and main scope, the hand control will ask if you want to add calibration stars. You may add as many as four, but I found three su� cient for excellent pointing accuracy.

Even at a magni� cation of 100×, anything I requested from horizon to horizon was in the eyepiece when the mount stopped. In the year that I’ve had the VX, it amazingly has never missed an object when I’ve been careful to do the alignment as outlined in the manual. � e only problem I have encountered has been the one-

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88 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

AS & T Test Report

guide any exposures. I mounted my Canon 60D camera

to the scope with a standard prime-focus adapter threaded onto the Edge Reducer, which replicates the normal SCT threads. The only problem I ran into was balance. The VX’s single counterweight was not heavy enough to balance the telescope in right ascension with the camera onboard. Fortunately, I had brought an additional 5-kg counterweight.

Because good tracking is critical for imaging, once the Go To alignment was complete, I performed the VX’s All-Star Polar Alignment procedure. After centring a star I chose from the hand control’s database, I completed

guide the VX. Today, that’s done with an autoguider camera that plugs into the VX’s autoguide port. You could use a separate small telescope to provide guide stars for the camera to monitor, but flexure between the main scope and guide scope can cause trailed stars. Enter the Celestron off-axis guider (OAG).

When I opened the box containing the guider, my heart sank. There appeared to be a million adapter rings and spacers. Luckily, the instructions

the process by re-centring it again using the mount’s altitude and azimuth adjusters rather than the hand control.

Preliminaries over, I sent the scope to M15 and began firing 30-second exposures. I shot twenty 30-second subframes of the globular. My stars were not quite round in all frames, but stacking these short exposures into a finished picture yielded pleasing images. What’s amazing is that a beginner could have achieved similar results. I didn’t do anything special; I just snapped away.

The Off-Axis GuiderIf you want to go much beyond 30-second exposures, you’ll need to

The author imaged the Dumbbell Nebula (M27) through the Edge 800 setup. The picture is a stack of twenty 30-second unguided, prime-focus exposures using the Edge f/7 focal-length reducer.

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for con� guring the OAG for my setup were clear. � ree setscrews attached the camera to the guider body. I prefer a more secure connection, but it caused no problems and I was impressed by the OAG’s otherwise he� y construction and quality � nish.

My pictures with the guider weren’t award winners because I was imaging from my light-polluted backyard under a full Moon. And I did have one scare — when I began autoguiding at � rst, the guide camera didn’t pick up a single star. It turned out that my autoguider wouldn’t reach focus without an extension tube due to the presence of the Edge reducer. With the guider inserted into the tube from an old Barlow, the OAG worked well, keeping stars respectably round.

The StarSense AutoAlign CameraCelestron’s StarSense accessory mounts to the Edge’s tube in place of the telescope’s 50-mm � nder and automates the Go To alignment process. � e box contained a small camera and a replacement NexStar hand control. Connect the StarSense controller in place of the original, hook the camera to one of the mount’s auxiliary ports, and you’re ready to go.

I was skeptical that such a seemingly simple gadget would enable the VX to align itself. Nevertheless, it worked. I turned on the mount, entered the date, time and city, and selected Auto Alignment. StarSense directed the mount to take images of star � elds on both sides of the meridian. Despite a bright Moon, the camera was sensitive enough to acquire 40 to 100 stars every time. In only three minutes the StarSense indicated that the VX was aligned. We’d see about that.

I punched in M13. � ere it was near the centre of the � eld of a 20-mm eyepiece at 100×. M57? Same. M3? Yep. Every single object I chose from horizon to horizon was in the eyepiece. Go To accuracy seemed just as good as with alignments done the old-fashioned way.

Not that the StarSense was perfect. My eyes had di� culty with the display’s small fonts. More signi� cantly, the StarSense’s All-Star polar-alignment routine didn’t work. � e results it yielded were inaccurate — it put the telescope degrees away from the celestial pole. I contacted Celestron technical support, who assured me they were working to make All-Star functional by the end of 2014. Even without All-Star, however, the StarSense was amazing. Not only did it align the VX as well as I could, it was just so cool.

� e VX mount is not a caviar-class GEM, but it makes up for that with its low price, portability, and solid performance. � row in the optically impressive Edge 800, the Edge Reducer, the o� -axis guider, and the StarSense, and a novice — or an old hand — will be equipped with a system ready to take on almost any task for a price lower than I would have thought possible. �

Contributing editor Rod Mollise writes an entertaining astronomical blog at www.uncle-rods.blogspot.com.

WHAT WE LIKE:

� Good construction quality with large, clear aperture

WHAT WE DON’T LIKE:

� Camera and T-ring attach to off-axis guider with less-than-secure setscrews

O� -Axis Guider

The author’s image of globular cluster M15 consists of twenty 30-second, stacked, unguided, prime-focus f/7 exposures.

WHAT WE LIKE:

� Completes a good Go To alignment in 3 minutes

WHAT WE DON’T LIKE:

� The All-Star polar-alignment feature did not function

StarSense Auto-Align Camera

The Celestron StarSense camera takes the place of the standard 9x50-mm fi nder when used. This camera automates the Go To alignment process.

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90 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Gallery

▴BATTLING BEACONSAlun DaviesVenus competes with the lighthouse at Cape Schank in Victoria. Alun used a Nikon D600 on a tripod with a 18-35 Nikkor lens at 18mm. Manual exposure at f/4 ISO 250 for 30 seconds. Processing in Lightroom and Elements.

HOW TO SUBMIT YOUR IMAGESImages should be sent electronically. Please fi rst send a low-res JPG version to [email protected], and we’ll get back to you with information on how to send your hi-res versions if selected. Please provide full details of all images, eg. date and time taken; telescope and/or lens used; mount; imaging equipment type and model; fi lm (if used); fi lter (if used); exposure or integration time; and any software processing employed. Readers who have a contributed image published in Australian Sky & Telescope will receive a 3-issue subscription to the magazine.

Astrophotos from our readers

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GLOBULAR GLOWDylan O'DonnellGlobular star cluster Messier 22 is just over 10,000 light-years from Earth. Dylan used a Celestron 9.25" SCT on a CG-5 mount, focal reducer, Canon 70D with BackyardEOS software. Exposure was 10x 30s at ISO 1600, unguided, and stacked in Nebulosity.

◀RED MOONCecilia WattersThe Moon moved through the Earth's shadow on October 8, 2014, with an eerie red result. Camera used was a Nikon Coolpix P510 on a tripod. Exposure was 1/100th-sec, f/3 at ISO 800.

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Gallery

▴EDGY GALAXYJohn DolbyKnown variously as the Silver Coin galaxy, Silver Dollar galaxy, Sculptor Galaxy and NGC253, this galaxy is a little over 11 million light-years from Earth. The image is a combination of 102 images for a total exposure time of 2.8 hours using a QSI 583 camera and Maxim DL Pro V5 software. Processed with Pixinsight, GradientXterminator, Neat Image and Adobe CS5. Telescope was a Celestron 11" SCT with Celestron CGE Pro mount on a Southern Cross Pier.

◀SOLAR FLAIRPaul MartinaitisTaken with a Lunt 60 (Single Stack) solar telescope using a 2.5x Barlow and DMK51 camera. For this nine-panel mosaic, Paul chose the best 100 of 600 frames for the solar prominences, and the best 100 of 1,200 frames for the disc. Software processing using AS!2 and Photoshop 6.

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www.skyandtelescope.com.au 93

▶DISAPPEARING ACTWill Vrbasso

Saturn slipped behind the Moon on August 4, 2014. Will captured the scene using a Canon EOS6D camera through a 6mm eyepiece on a 15cm Newtonian telescope. Exposures at

ISO12800 were 1/160th sec for the Moon and 1/60th sec for Saturn. Processed in Photoshop.

▴ORION NEBULARoger GifkinsThe famous Messier 42 is a perennial favourite with astrophotographers. Roger used a TSA 102 refractor, Moravian G2-4000 CCD at -20C, Paramount PMX+, LRGB exposures of 43:24:24:24 minutes (4 min subs all unguided), and processed the image in Nebulosity and Photoshop.

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94 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

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96 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

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Eyes On The Sky DVDThis 60-minute produced by the European Southern Observatory (ESO) covers the history of the telescope, its importance, and some of the technological breakthroughs. $11.95

The Universe DVDThis 128-minute DVD features discoveries from the Hubble Space Telescope about star clusters, nebulae, extrasolar planets, galaxies, dark matter, the Big

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Star Charts A series of 18 maps (nine double-sided A4 pages) + CD covering the entire sky. The charts have a water-resistant laminate coat to make them more durable when used outside. An additional reference guide provides an overall view of all 18 charts and an index to the constellations and major stars. $19.95

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Advertisers Index Australian Sky & Telescope magazine acknowledges and thanks the advertisers who appear in this issue. Speciality astronomy equipment manufacturers and dealers are an important resource for astronomers. We encourage you to visit the advertisers in this issue and benefi t from their experience.

Advanced Telescope Supplies ........................ 63 Astronomical Society of Australia ................. 35 AstroShop ........................................................ 53, 95 Australian Sky & Telescope ........................ 65, 96Finger Lakes Instrumentation .....................3, 94 Journeys Worldwide ........................................... 67

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Page 98: Australian Sky & Telescope -2015

98 AUSTRALIAN SKY & TELESCOPE FEBRUARY/MARCH 2015

Focal Point Damian G. Allis

Stu’s Last Lesson

Stuart Forster (known to friends as Stu) was a mentor, educator, and a highly regarded amateur

astronomer. It came as a great shock in January 2011 when we learned of his sudden passing at age 55, having just retired from his medical practice to spend more time with his family, telescopes and imaging software.

Although Stu’s family appreciated his celestial activities, his familiarity with his equipment was his own. He had more than a dozen scopes, dozens of eyepieces and filters, six CCD rigs, two domes, 400 books, S&T back to 1964 . . . you get the idea. Stu was unique for the size of his collection, but the problem of dealing with specialised equipment when the unexpected occurs is one that all amateur astronomers risk sharing.

Ryan Goodson and I have helped Stu’s family sell his collection. As we have gone through this process, we’ve learned that you can make the lives of your family and fellow astronomers much easier by taking stock of what you own. If you weren’t here tomorrow but your gear was, how much work would it be for someone else to deal with it? We recommend you consider the following:1. Keep a list of everything and let someone know that this list exists and where he or she can find it.2. If it’s valuable, say so. If it can be thrown away, say that, too. 3. If you can’t keep the original boxes, use containers to keep grouped items together. Stu kept Tupperware in business by placing complete sets of tools and components into labeled containers.4. As you organise or modify your collection, take a picture of complete sets of similar objects, then add image labels and descriptions to your inventory. You instantaneously make a mountain a molehill.5. Stu’s collection was excessive in some respects, but he wasn’t just an observer. He was the closest thing our region had to an equipment library where people could pick up a piece of astronomy equipment on loan,

In case of the unexpected, make it easier to distribute your astronomy possessions.

Astronomy club members from far around are putting Stu’s gear to good use.

websites when I started selling Stu’s equipment. I was sent take-down notices within hours because I wasn’t selling my own stuff and didn’t have seniority enough to post my announcement in the classifieds section. Two years later, and we’re still sorting out items and finding ways to sell them.8. Keep books and magazines in the local area. See if your local public library or high school accepts donations.

If you have other helpful ideas, please find a way to add them to this list and let others know! ✦

try it out and bring it back (usually). Consider the possible future of your equipment.6. Join a club! Your local astronomical society is a support group for others who share your passion. It’s also the first place your family can go to when they start selling stuff. We’re happy to say that astronomy club members from far around are putting Stu’s gear to good use.7. Be aware that proper distribution will not be easy. I posted announcements on several astronomy

Damian G. Allis is a research professor of chemistry at Syracuse University and a fellow with the Forensic and National Security Sciences Institute. He is director and co-organiser for CNY Observers & Observing (www.cnyo.org) and a 2014 NASA Solar System Ambassador.

DAMIAN G. ALLIS

Page 99: Australian Sky & Telescope -2015

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