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FEATURED DEALERS: MeadeTelescopes Adelaide Optical Centre | www.adelaideoptical.com.au MeadeInstrument The Binocular and Telescope Shop | www.bintel.com.au MeadeInstruments www.meade.com Sirius Optics | www.sirius-optics.com.au May | June 2016 ISSUE 93, VOL. 12, NO. 4 Contents
REGULARS 5Spectrum By Jonathan Nally 8NewsNotes 12 Discoveries 40 New Product Showcase 41 Cosmic Relief 74 Astro Calendar
FEATURES Looking back in time p.14 14 Mapping the cosmos’ primordial sound waves OBERVING & EXPLORING Astronomers are combing through the largest map of 42 Binocular highlight galaxies ever produced to find M46 and M47 in Puppis the echoes of ancient sound By Gary Seronik waves. By Daniel Eisenstein 44 Tonight's sky 20 Untwinkling the stars A secret stellar flame How did the world’s largest By Fred Schaaf telescopes conquer the 46 Sun, Moon and planets tempestuous atmosphere? Mars and Saturn at opposition By Shannon Hall By Jonathan Nally 28 Anomalous appearances 47 Meteors Will modern observations of the Keep an eye out for sporadics Mercury transit stack up to the By Con Stoitsis historical record? By Thomas Dobbins 48 Double star notes p.56 Galaxies galoreinVirgo 32 Choosing a camera for More of the Centaur’s gems astrophotography By Ross Gould The question isn’t which is best, 49 Comets but which is best for your goals. Bright prospects for comet 52 Targets ByRichardS.WrightJr. viewing Sights in Leo’s starry sickle 38 Shoot the Moon with a By David Seargent By Sue French smartphone 50 Variable stars 56 Big fish, small tackle It’s easy to take high-quality Going all hyper over 766 Drop a line into the deep pool images of the lunar disk. Centauri of the Virgo Galaxy Cluster. By Richard Jakiel By Alan Plummer By Mathew Wedel
4 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 SPECTRUM JONATHAN NALLY In praise of the Moon he Moon is usually the first astronomical body that astronomers get to know. Just ask Galileo, who aimed his telescope at the lunar surface and set off Ta scientific revolution that would eventually sweep away aeons of celestial superstition and the Earth-centric model of the cosmos. The Moon is up there in the sky, unchanging, sometimes at night, sometimes during the day, and the beauty of it is that you don’t need a telescope to begin your initialreconnaissance—thenakedeyealoneisenough.Butprogressiontobinoculars andthenatelescoperevealsaworldfullofsurprises—mountains,valleys,rilles, p.66 Photographing the Moon craters big and small, and majestic sweeping plains. There’s enough there for a lifetime of study. It’sagreattargetforphotographytoo.Andwithalmosteveryonecarryingacamera THE ASTRONOMY SCENE around in their pocket these days, there’s really no excuse for not giving it a go. 62 Test report Whetherit’sasimplepanoramicviewoftheMoonshiningbrightlyoverabayor amountain,oracloseupshottakenbyholdingasmartphoneuptotheeyepieceof Meade’s 25-cm LX600-ACF By Dennis Di Cicco atelescope,easylunarphotographyisnowavailabletoeveryone.Onpages38-39we walk you through the steps of simply lunar photography, while for more detailed work, 66 Imaging Luna see our in-depth article beginning on page 64. Plus, if you’re in the market High-resolution close-ups of foranewcamera,ourbuyersguidebeginningonpage32willgetyougoinginthe theMooncanbeasatisfying right direction. challenge for modest apertures. By Robert Reeves Jonathan Nally, Editor 72 Telescope workshop [email protected] A50-cmdreamtelescope By Gary Seronik
76 Gallery THE ESSENTIAL MAGAZINE OF ASTRONOMY Reader's astrophotos Australian Sky & Telescope is on Facebook. Complementing our 79 Marketplace website, Facebook helps keep you alerted to astronomy news and information about Australian Sky & Telescope. 80 Indextoadvertisers EDITORIAL Printed by Webstar 82 Focal Point EDITOR Jonathan Nally Australia distribution by Network ART DIRECTOR Lee McLachlan Services. New Zealand distribution by Plutoisnottheend CONTRIBUTING EDITORS Gordon & Gotch. © 2016 F+W Media, By Emily Lakdawalla John Drummond, David Ellyard, SKY & TELESCOPE Inc. and Paragon Media. No part of Ross Gould, Steve Kerr, INTERNATIONAL this publication may be reproduced, Alan Plummer, David Seargent translated, or converted into a machine- EMAIL [email protected] EDITOR IN CHIEF readable form or language without Peter Tyson the written consent of the publisher. SUBSCRIBE TO AS&T ADVERTISING EDITORIAL Australian Sky & Telescope is published ADVERTISING MANAGER Jonathan Nally SENIOR EDITORS by Paragon Media under licence from 75 Subscription offer EMAIL [email protected] Alan M. MacRobert, J. Kelly Beatty F+W Media, Inc. as the Australian edition of Sky & Telescope. Australian Sky & SUBSCRIPTION SERVICES EQUIPMENT EDITOR Sean Walker Subscribe and receive FREE SCIENCE EDITOR Camille M. Carlisle Telescope is a registered trademark of TEL 02 9439 1955 F+W Media, Inc. USA. Articles express Hubble Space Telescope DVD! EMAIL [email protected] WEB EDITOR Monica Young OBSERVING EDITOR the opinions of the authors and are not necessarily those of the Editor or Paragon PARAGON MEDIA PTY LIMITED Susan N. Johnson-Roehr Media. ISSN 1832-0457 ABN 49 097 087 860 SENIOR CONTRIBUTING EDITORS ON THE COVER TEL 02 9439 1955 FAX 02 9439 1977 Robert Naeye, Roger W. Sinnott ADDRESS Suite 14, Level 2/174 Willoughby Rd, DESIGN DIRECTOR Crows Nest NSW 2065 Patricia Gillis-Coppola AUSTRALIAN SKY & TELESCOPE How ground-based observatories PO Box 81, St Leonards, NSW 1590 ILLUSTRATION DIRECTOR (ISSN 1832-0457) is published 8 times are becoming better than the Hubble Gregg Dinderman per year by Paragon Media Pty Limited, PUBLISHER Founded in 1941 by Charles A. Federer Jr. © 2016 Paragon Media Pty Limited. Space Telescope. See page 20. Ian Brooks and Helen Spence Federer All rights reserved.
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The six most distant known objects in the SolarSystem of this having occurred by chance. have orbits (shown in purple) that remain beyond Neptune Moreover, these copycat orbits couldn’t and which align in one direction. A hypothesised simply be a holdover from the Solar 2013 RF 98 massive planet (orange orbit) could be maintaining System’s formation — over time, subtle this perplexing alignment. perturbationsfromthegiantplanets 2004 VN112 would cause them to slowly drift apart. 2007 TG422 2012 VP113 Instead, something must be actively imposing this orbital order. Batygin and Brown invoke a massive hypothetical body,whichthey’vedubbed‘PlanetNine,’ 90377 Sedna with at least 10 times Earth’s mass (two to “Planet Nine” four times its diameter). It would occupy ahighlyelongatedorbitthataverages about700a.u.fromtheSunandnever comesnearerthanroughly300a.u. 2010 GB174 Such an object would naturally explain not only the clustered perihelia but also thepuzzlingorbitsofSednaanditskin. Sowhereisthisputativeplanet? Actually,awiderangeoforbitsispossible, CALTECH/ROBERTHURT with periods ranging from 10,000 to 20,000 years. The Batygin-Brown prediction requires a highly elongated Does the Solar System have a ninth planet? orbit, which means that most of the time the object lingers near aphelion. oesamassive,extremelydistant might be responsible. So it should be no brighter than roughly DplanetorbittheSun?Anew Batygin and Brown have taken this magnitude22—beyondtherangeofmost analysis of distant Solar System ideatothenextlevel.Theiranalysis ground- and space-based surveys to date. orbits argues that it should exist. showsthattheSolarSystem’ssixmost Eveniftheproposed‘PlanetNine’is WritinginFebruary’sAstronomical distant objects not only have clustered neverseendirectly,thecircumstantial Journal,KonstantinBatyginandMichael arguments of perihelion (asit’sknown case for its existence might be Brown (Caltech) describe how Kuiper technically) but also follow elliptical strengthened once observers discover Beltobjectsthataverageatleast150 orbits orientated the same way in space, more very distant Kuiper Belt objects and astronomical units from the Sun and angled below the ecliptic plane by assess their orbital distribution. nevercomecloserthanabout50a.u. about 30°. There’s only a 0.007% chance ■ J. KELLY BEATTY share an interesting dynamical property. Their perihelia (closest orbital distance to theSun)allclusterneartheeclipticplane —andthey’reallmovingsouthtonorth Hunting for putative planets of Proxima Centauri when they pass through perihelion. This orbital clustering started to Astronomers are ramping up their search #PaleRedDot.Meanwhile,Proxima command attention after the discovery for exoplanets orbiting the nearest star Centauri’s passage in front of a oftheobject2012VP113 afewyearsago. toourSolarSystem.ThePaleRedDot background star in February gave the Inannouncingthatfind,Chadwick initiative, led by the European Southern Hubble Space Telescope an opportunity Trujillo (Gemini Observatory) and Scott Observatory,isacampaigntoexamine to look for microlensing events. These Sheppard (Carnegie Institution for thereddwarfstarProximaCentauri are small spikes in the background star’s Science) noted the perihelic similarity for exoplanets using the radial velocity brightness that a planet orbiting the red of 2012 VP113,90377Sednaand10other method, which teases out the signal of dwarfcouldproduceasitpasses in front of bodies. Moreover, these objects occupy aplanettuggingonitshoststar.You the star, magnifying the starlight as a lens adynamical‘noman’sland’thatdefies can follow the Pale Red Dot campaign would. Read more about the endeavours at easyexplanationforhowtheygot on the project’s website, palereddot. http://is.gd/proxcen2016. there. Trujillo and Sheppard concluded org,orbyfollowingtheTwitterhashtag ■ DAVID DICKINSON thatamassiveplanet,evenfartherout,
8 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 The Milky Way’s Spotting ‘twins’ of Eta Carinae galactic hit-and-run few hundred million years ago, a Asmall galaxy had a fender-bender with theMilkyWay.Evenasitfledthecrime scene,itsentripplescoursingthrough the Milky Way’s disk. Nowwiththehelpofatrioofbrightly pulsating stars, Sukanya Chakrabarti (Rochester Institute of Technology) and
(GSFC AND ORAU) colleagues say they have found the fugitive dwarf galaxy. Last year, Chakrabarti and her team Eta Twin-4 Eta Twin-5 found four stars located toward the The galaxy M83 hosts two potential constellation Norma — the exact spot ‘twins’ of Eta Carinae. These candi- dates (insets, not resolved) seem to where,backin2009,sheandLeoBlitz have warm, dusty shrouds much like (University of California, Berkeley) had theonethatenvelopsEtaCar. predicted the runaway galaxy is hiding. The astronomers hoped the four stars were
NASA / ESA / HUBBLE HERITAGE TEAM / R. KHAN 2 arcseconds Cepheids, standard candles that regularly expand and contract at a rate directly Astronomers looking for clones of the million light-years away: M51, M83, related to their intrinsic brightness. If so, huge,unstablestarEta(η)Carinaehave M101 and NGC 6943. Together, these the team would be able to use the stars’ potentially found five in other galaxies. galaxies produced 20 of the Type II (core- variations to confirm their distances. EtaCarisoneofthemostmassive collapsing, big-star-killing) supernovae Butsincethen,adebatebetween starsintheMilkyWay,estimatedto seeninthelastcentury.Andhereis Chakrabarti’s team and that of Pawel have 120 Suns’ worth of material. It where the astronomers found five objects Pietrukowicz (Warsaw University pumps out more than 5 million times that look just like Eta Car. Observatory, Poland) has arisen over theenergythantheSundoes,butitand ‘Look just like’ is used loosely, Khan whether the stars are true Cepheids. Due its companion star hide inside a double- explainedduringapressconferenceat to the Polish team’s work, three of the four dumbbell of dust and gas called the the American Astronomical Society’s starswererejected. Homunculus Nebula. biannualmeeting.Thefiveobjectsare Chakrabarti’s new study, announced Astronomers haven’t seen any stars toodistanttoberesolved.Butthelight atthewinterAmericanAstronomical quitelikeEtaCar,buttheywantto.Such coming from these sources behaves SocietymeetinginKissimmee,Florida, massive, evolved stars produced many of just like that from Eta Car. The sources addstwonewstarstothelistofpotential our galaxy’s heavy elements, and these are relatively faint in near-infrared and members of the sought galaxy. But it’s still megastars might also be the culprits visiblelight,asseenbytheHubble unclear whether these three candidates behind what are called superluminous SpaceTelescope,butthey’rebrightat areCepheids;theycouldbebinaries or supernovae, stellar explosions that are mid-infrared wavelengths, as seen with starswithdarkspotsonlymimicking a strangelybrightcomparedwiththeirkin. theSpitzerSpaceTelescope.Moreover, Cepheid’s pulsation. Observers haven’t had much luck their brightness ‘flattens out’ in this Whetherornotthetrioproveto be looking for Eta Carinae’s twins, though mid-infrared range, in a manner that’s Cepheids, Chakrabarti does think they they’veturnedupseveralcandidates. a spot-on match for star-enveloping are a good starting point. Follow-up RubabKhan(NASAGoddard)andhis dust that’s been warmed to between observations of the shift in the stars’ team are narrowing the search by looking 400and600kelvin. spectral lines reveal velocities that all inothergalaxiesfordust-enshrouded Thus, the team members are pretty clockinatroughly156kilometres per starswhosevisibleandinfraredlight surethey’reseeinglightfrommassive, second—anorderofmagnitude larger closely matches Eta Car’s. evolvedstars,astheyalsoexplaininthe thantypicalvelocitiesofstarsinthe disk Theteamlookedatfourbright,star- journal Astrophysical Journal Letters. ofourgalaxy.Sotheyclearlydon’t belong formingspiralgalaxiesthatlie15to26 ■ CAMILLE M. CARLISLE to the Milky Way. ■ SHANNON HALL
www.skyandtelescope.com.au 9 News Notes
Martian gullies triggered by dry ice? esearchersarecirclingbacktothe gullies are evolving right now —cutting Ridea that carbon dioxide ice might be more deeply into their surroundings responsible for some or all of the gullies and creating aprons of debris farther onMars.In2000,imagesfromNASA’s downslope, sometimes more than once. Mars Global Surveyor revealed hundreds Modern-day Mars is far too cold and dry of these features, trailing down crater to harbour the substantial near-surface rimsallovertheRedPlanet.Theylooked reservoirs of liquid water that could geologically fresh, cut into older terrain yet explain this behaviour. largelyfreeoferosion. In the January issue of Nature Geoscience,
Thesegulliesaredifferentfrom researchers Cedric Pilorget (IAS/CNRS, NASA / JPL / UNIV. OF ARIZONA (and much larger than) the occasional, France) and François Forget (LMD/CNRS, Images taken in 2010 (left) and again in 2013 seasonal trickles of salt-infused water seen France) suggest a formation scenario that by NASA’s Mars Reconnaissance Orbiter show elsewhere on the surface, which create the involvesnowateratall.Instead,theyinvoke that an existing gully recently formed a new branch (indicated by the arrow). so-called recurrent slope lineae. frozen carbon dioxide (‘dry ice’), which coats Initial speculations focused on the all of the Martian polar terrain each winter allow sunlight to pass through to ground idea that water was seeping out onto and even extends to poleward-facing slopes level. Ice in contact with the Sun-warmed the surface and cutting little channels at lower latitudes. This explanation builds soil sublimates into gas but remains as it flowed downslope. Yet many gullies on a dry-ice-powered process first proffered trapped under the overlying slab. Gas occur in frigid polar regions or on heavily by University of Melbourne researcher Nick pressure builds and eventually lifts and shadowed slopes facing toward the poles. Hoffman in 2002. cracks the slab, causing the trapped gas The‘gullydebate’reignitedlast Careful modelling by Pilorget and (along with entrained dust) to cascade year when images from NASA’s Mars Forget shows that the annual frosting of downslope, forming or enlarging a gully. Reconnaissance Orbiter showed that many dry ice can become transparent enough to ■ J. KELLY BEATTY
Limit on black hole gluttony. Once a The disappearing quasar This isn’t the first case of a black hole reaches about 50 billion times Astronomers tracking a distant quasar disappearing quasar; astronomers now the mass of the Sun, the disk of gas over a span of 13 years have reported that know of several ‘changing look’ active that acted as its dinner buffet begins to all signs of it have disappeared. galaxies (as they’re collectively known). crumbleapart.AndrewKing(University The quasar, known as SDSS The best explanation for J1011+5442’s of Leicester, UK) presents this conclusion J1011+5442, was first detected in 2002. A disappearance is a diet, in which the black IN BRIEF IN in the journal, MonthlyNoticesLettersof follow-up spectrum collected the next year hole cut its feeding rate by a factor of 10. the Royal Astronomical Society.Amore showedallthesignsofhotgasfeedinga The accretion disk should still surround massiveblackholewillhavealarger typical, ferociously gobbling supermassive it, though. The outermost part of the disk, disk feeding it than a smaller hole will. blackholesittingatthecentreofagalaxy. which is responsible for the light, would ButKingcalculatesthat,abovethelimit, The quasar’s brightness declined normally take 800 years to gradually the disk’s gas will collapse into clumps, steadily over the next decade, far more emptyoutandfade,Runnoe says. Instead, formingstars.Tocontinuegrowing,the systematically than usually happens she suggests that rather than clear its plate black hole would need to swallow clumps with such objects. When Jessie Runnoe completely in the few short years they’ve (orstars)whole.Sincetheglowfrom (Penn State University) and colleagues been observing, the quasar swallowed those disks is what enables observers to observed the quasar again as part of the the nearest, hottest gas from the inner ‘see’ these dark objects, more massive Time Domain Spectroscopic Survey in accretion disk. This could happen quickly, blackholesmightbetrulyinvisible: 2015,theytookavisible-lightspectrum in a month or two. The hot, inner gas astronomers would need to turn to more of the beast’s disk of gas. They found would have emitted ultraviolet light as it indirectmeans,suchasgravitational nothing—almostallsignsofthequasar swirled toward the black hole, irradiating lensing, to find the biggest behemoths. hadvanished.Instead,theysawonly the outer disk to make it glow. So when the Gas disks have revealed black holes up arelativelyordinarygalaxy.Theteam ultraviolet beacon near the black hole went to around 10 billion solar masses. publisheditsresultsintheJanuary11 dark, the outer disk would have lost its ■ ALLEN ZEYHER issue of the Monthly Notices of the Royal visible-light shine as well. Astronomical Society. ■ MONICA YOUNG
10 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 96>,(*2,94(55 :*/40+;(:;96.9(7/ *.,79646<5;
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Mars’ enormous canyon, Valles Marineris, as seen by NASA’s Viking spacecraft in the 1970s.
First forays to the Red Planet ARIZONA / -CALTECH STATE UNIVERSITY NASA /NASA JPL Mars has been the focus of attention for more than 50 years.
he pace of exploration of trouble. Their very first mission blanketed by a planet-wide dust Mars, the fabled ‘Red Planet,’ in 1960 failed even to reach Earth storm that took a month to clear. Thas quickened greatly in orbit.Thenextfouralsofailed, When the surface at last came into recent decades. A new European- includingMars1.Mars2gotthere view, the sight was breathtaking. Russian mission (ExoMars, but did not complete the job. We saw for the first time the launchedMarch14)isnowon TheUSalsolostitsfirstfly-by 5,000-kilometre-longchasm its way to orbit the planet and mission (Mariner 3) but had more along the equator, later named ‘lookforsignsoflife.’Alander success with Mariners 4, 6 and Valles Marineris (Mariner Valley), is programmed to follow. They 7 (the missing numbers indicate and which makes Earth’s Grand will join a substantial assembly of failures or different destinations). Canyon look like a scratch. missions already in place, mostly These fly-by probes returned the We also saw the 20-kilometre- from the US, with more to come. first grainy images of parts of the high, 1,000-kilometre-wide volcano Itisinterestingtolookbackto surface of Mars. Olympus Mons, three huge where all this began. The last few TheSoviet’sMars3hadamore- volcanoes along the Tharsis Ridge days of May 1971 are a good focus dauntingdoubletask:toorbitthe nearby, vast lowland basins, and what and a reason to reminisce in this planet and drop a lander to the looked like dried-up beds of rivers issue. Two significant missions surface. Arriving on December and seas on a planet now apparently were launched very close together, 2, 1971, it completed both, but bone-dry. Over time, Mariner theSoviet’sMars3onthe28th,and the lander soon failed. Only 20 completed the first photographic theUSMariner9onthe30th.Both seconds of video data reached the survey of the whole planet. were important scientific missions orbiter. It was, however, the first With these two missions, the butalsohadpoliticalaimsaspartof successful landing on Mars (Mars serious investigation of Mars had theongoingColdWarinspace,the 2’s lander had crashed). The orbiter begun. Five years later, the US US having won the race to the Moon continuedtoreturndataonsurface would land its two Viking probes, a couple of years earlier. temperatures and atmospheric which would return some still- TheMissiontoMarshadbegun composition for another year. puzzling indications as to whether in the previous decade, with both Though sent off a few days later, the planet is an abode of life. nations launching probes from Mariner9hadtakenafastertrack The momentum to explore 1960 onwards. The initial objectives than Mars 3 and arrived three weeks and understand Mars now seems were modest, aiming for simple earlier. On November 13, 1971, it went unstoppable. The planet is currently fly-bys, but success was far from into orbit around the planet and a busy place, and the pace will not assuredinthosepioneeringdays, become its first artificial satellite. It slacken in the foreseeable future. onlyafewyearsafterSputnik1had carried more scientific instruments trodden the first path into space. than the Russian craft, and the David Ellyard presented SkyWatch on Thetechnologywasnotyetreliable. world was waiting for the pictures. ABC TV. His StarWatch StarWheel has TheSovietssufferedthemost At the time of arrival, Mars was sold over 100,000 copies.
12 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016
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()9F6! 7! :!9F:(!F"!!.F2"F2 9!7@*1'F)1F:(!F ;(62?'(F:(!F42//?=21F;2F 6*1'F2 9!6@*1'F F$2 /F/!1':(F2#F 72?1 F 00F7)'(:F ")!/ F;(72?'(F F@!7CF/ 6'!F;!/!9 24!F21/CF -F;2F2?6F?6 1F 7! 9F ;(62?'(F;2F 00F:FA27-9FA*:(F .: EF ?9)1'F0? (F027!F02 !9:F!5?*40!1:F 2?F #36-02?1:! F:!/!9 24!9F 9FA!/.F 9F 9: CF 211! :! F:2F;(!F1*'(:F9-DFA ; (*1'F :F .92F(!.49FC2?F9( 6!F;(!F 6! ;(: -*1'F !5? ;26* .F02?1:9F 9F/21'F 9FC2?F 1F 9 :!//):!9F 7)" MAPPING THE COSMOS’ Primordial Sound Waves DANIEL EISENSTEIN Astronomers are combing through the largest map of galaxies ever produced to find the echoes of ancient sound waves. Illustration by Casey Reed 14 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 n the Sacramento Mountains near Cloudcroft, Each region of the early universe produced such New Mexico, the Sloan Digital Sky Survey (SDSS) a sound wave. Initially, those waves rushed about has been charting the cosmic web of galaxies in in the plasma-filled universe. There were no stars the largest map ever produced. Conceived in the or galaxies yet in that dense, hot place. Electrons Imid-1980s, the SDSS saw first light in 1998 and soon and nuclei couldn’t separate far because of their brought astronomy to mass-production mode. The electrostatic attraction, but it was too hot for them to collaboration now includes some 1,000 astronomers settle down into atoms. Meanwhile, photons within from more than 50 institutions worldwide, and they’re the soup couldn’t move far before scattering off an tackling a grand goal: measuring the faint imprint of unbound electron. cosmic sound waves that reverberated throughout the In this tightly coupled system, pressure fluctuations universe during its first 380,000 years. (aka sound waves) carried electrons and nuclei along In 2014, SDSS announced a new map that charts with them, leaving the dark matter unaffected. The the locations of 1.5 million galaxies within a volume primordial soup was so hot that the speed of sound equivalent to that of a cube 7.5 billion light-years on a reached 57% of the speed of light. Because scientists side. This project is known as the Baryon Oscillation refer to protons and neutrons as baryons, these early Spectroscopic Survey (BOSS), and it aims to shed light sound waves are called baryon acoustic oscillations. on the nature of dark matter and dark energy and the But as the universe expanded, it cooled. Eventually, fate of the universe itself. 380,000 years after the Big Bang, atoms began to form. With no free electrons to scatter them about, the Sloshing in the primordial soup photons finally flew free; the neutral cosmic gas, no Today’s universe is filled with structure at cosmic longer interacting with the photons, could no longer scales — giant clusters, filaments and walls of galaxies feel their pressure. The sound speed plummeted and separated by voids as large as 200 million light-years the spherically outgoing waves stalled. across. This cosmic web doesn’t come from recent Over the first 380,000 years, the waves had travelled interactions between galaxies — it arose in tiny density an enormous distance, and even after stalling, their variations in the young, hot and plasma-filled universe. effects expanded along with the universe. One such By studying the arrangement of relatively nearby expanding spherical shell would have a radius of 500 galaxies, cosmologists can reveal how those small, early million light-years today. seeds evolved over time. In the theory of cosmic inflation, the universe expanded at a gigantic rate for a fraction of a second almost instantly after the Big Bang. The simplest model says the observable universe grew from a size 100 billion times smaller than a proton to roughly a metre across. But due to quantum uncertainties within inflation, some regions grew slightly differently than others. Portions that expanded a little less emerged from the inflationary period denser than average, while other parts came out somewhat sparser. These initial density variations produced the main (3) actor of this story — sound waves. Even as inflation D. EISENSTEIN enhanced gravity-exerting clumps, the photons within those clumps produced enormous outward pressure. The opposing forces set particles and photons into VISUALISING SOUND WAVES A single disturbance (left) initiates a sound motion in the form of sound waves. The end of inflation wave, like a rock dropped in a pond. And like a ripple on the pond’s surface, that is similar to the popping of a balloon: the balloon’s disturbance propagates outward (centre). In the early universe, each region of the universe initiated its own sound wave, and the resulting ripples overlapped surface enforces a pressure difference, but once it (right). Each ripple has a radius of 500 million light-years in today’s universe, and breaks, the air inside expands and creates a sound wave overlapping ripples generate smaller (higher-frequency) overtones. To watch the that travels spherically outward. animation, go to http://is.gd/cosmicsoundwaves. MAPPING THE UNIVERSE (Facing page) This artist’s conception shows the Sloan telescope, which charted more than a million galaxies, represented by coloured dots, to reveal the imprint left behind by sloshing primordial plasma. SkyandTelescope.com April 2016 15 Seeing Cosmic Sound In 1970 Jim Peebles and Jer Yu, both working in the United States, and Rashid Sunyaev and Yakov Zel’dovich, both working in the Soviet Union, predicted that primordial sound waves would produce observable effects in today’s universe, affecting the large-scale distribution of galaxies. But astronomers hadtowaitthreedecadesfor data collection methods to reach the extreme level of sensitivity required to see these effects. 380,000 YEARS OLD The Planck satellite’s full-sky image Now, by precisely mapping the universe’s of the cosmic microwave background shows the universe galaxies and examining their arrangement in space, as it existed during the age of recombination, when protons astronomers can finally study the imprint those matched up with electrons and photons flew free. The primaevalwavesleftbehind.Galaxymapsthus inflation-enhanced temperature variations seen here (colder is blue, hotter is yellow and red) seeded the cosmic web of serveasatimemachinetostudytheearliestepochs galaxies we see today. of the universe. inflation-enhanced density fluctuations. These Seeing sound waves variations reveal a strong signature from primordial Weobserveprimordialsoundwavesintwoways. sound waves: just as ocean waves ripple sand, baryon The first method relies on sky maps that chart the acoustic oscillations resulted in hot and cold spots with a temperatureofthecosmicmicrowavebackground. typical angular size of about 1 degree. Thoughthebackgroundlooksnearlythesameinall The radius of these sound waves’ spherically directions, precise maps show minuscule variations expanding shells, 500 million light-years in today’s intemperatureofafewpartsin100,000duetothe universe, represents their fundamental length. As for a violin string, this length sets a fundamental tone as BARYON Galaxy Maps well as a series of higher-frequency harmonic overtones. ACOUSTIC OSCILLATIONS The Planck satellite has produced exquisite observations Today,apairof of the harmonies present in the temperatures it galaxies is most measures, providing a beautiful and compelling likely to lie 500 validation of the theory of the early universe. million light- In the second method, astronomers measure sound yearsapart.This waves’ effect on galaxy clustering in the SDSS maps. preferred distance (whiterings,left) Sound waves enhance the abundance of galaxies in a canbetraced specific pattern: any given pair of galaxies is slightly back in time to the more likely to be separated by 500 million light-years, cosmic microwave rather than 400 or 600 million light-years. Though background (right), this can’t be observed for an individual galaxy pair, the which immortalises the sound waves effect is detectable in large modern surveys with pairs that sloshed 3.8 billion years ago 5.5 billion years ago 13.7 billion years ago from hundreds of thousands of galaxies. The detection through the early E.M. HUFF / SDSS-III TEAM / SOUTH POLE TELESCOPE TEAM / ZOSIA ROSTOMIAN of this statistical effect serves as a ‘standard ruler’. universe. FROM DUSK Mapping the known universe UNTIL DAWN To measure the standard ruler of baryon acoustic The Sloan Digital oscillations, astronomers must construct vast maps Sky Survey of the galaxies that are strewn far and wide across the Telescopeisa universe like so many grains of sand. So how does 2.5-metre f/5 Ritchey-Chrétien SDSS make these maps? telescope with a The survey uses a custom-built 2.5-metre f/5 3-degree field of Ritchey-Chrétien telescope. A large secondary mirror view.Ratherthan and two correcting lenses supply a 3-degree field of sitting enclosed view. While the primary aperture isn’t large for a inadome,the telescope is research telescope, the product of aperture and field of protectedbya view enables the telescope to rapidly survey the sky. wind baffle. DAVID KIRKBY The original SDSS project relied on two 16 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 N LABORATIO ESA / PLANCK COL instrumentsthatcouldeachbemountedonthe telescopeinturn.Thefirstwasalargeimaging camera, the largest digital camera of its day with 126 () megapixels. Over the course of the survey, SDSS has imaged more than a third of the sky through five filterscentredat355,469,617,748and893nanometres. Ithasrecorded1.2billiondetectionsfrom470million D. EISENSTEIN SDSS / uniqueobjects.RoughlyhalfoftheseareMilkyWay LARGE-SCALE STRUCTURE Are galaxies distributed randomly in our universe? stars; most of the rest are galaxies. The answer is a decided ‘no’. Randomly plotted points (left) contrast with an actual The second instrument was an optical spectrograph map of almost 50,000 galaxies at a redshift of around 0.5 (right), whose light has been travelling for about 6 billion years to reach Earth. The right-hand image is that takes an object’s light and disperses it into about 3 billion light-years wide, 4.5 billion light-years tall and 500 million light-years arainbow,enablingastronomerstomeasurethe thick. Each galaxy is colour-coded by its distance, with nearer galaxies yellow and intensity in roughly 2,000 wavelength bands. The farther galaxies purple. resultingspectrummayshowabsorptionoremission at specific wavelengths, corresponding to properties of rather than passing it through five imaging filters, the the atoms that are absorbing or emitting the photons. instrument needs more time to collect enough light Astronomers can then compare these spectral lines to in each band. The telescope produced images through referencevaluesanddeterminehowfasttheobjectis each filter in only 54 seconds, but a single spectrum movingawayfromus. typically requires 45 to 60 minutes. Moreover, a But though it’s rich with information, spectroscopy spectrograph capable of measuring all of the 200,000 is expensive in terms of exposure time. Because objects that fall in a single 3-degree field of view would the spectrograph splits light into 2,000 or so bands be very large and expensive. Measuring space with a standard ruler Measuring distance is one of the central even with one eye closed as long as you know teams of astronomers studying standard- problems in extragalactic astronomy. Though how intrinsically big something is. candle supernovae concluded that faraway astronomers can use redshifts to sort galaxies Accurate distance measures are vital explosions appear unexpectedly faint for their by distance — a higher redshift means a to determining the universe’s age and redshift. The discovery was shocking: it means galaxy’s light has travelled a longer way composition. For example, a universe that the universe’s expansion is accelerating, through our expanding universe — redshift contains more matter will expand more and probably driven by some repulsive force that does not measure distance directly. more slowly because of that extra matter’s acts only on the largest scales. Dubbed dark Standard phenomena provide other ways gravity. If you measure the redshift of an energy, this discovery, recognised by the to measure distance. Standard candles are object in this universe, the distance to that 2011 Nobel Prize, presents one of the leading objects of known luminosity. If we measure object would be shorter than if the expansion mysteries in modern physics. their apparent brightness and know their had continued unabated. Said another way, Years ago standard candles revealed the intrinsic brightness, we can infer their a standard candle at a given redshift would presence of dark energy. Now the BOSS distance. Standard rulers are objects of known appear brighter in a slowing universe than in project is helping us to use the universe’s size. We can infer their distances by their a continually expanding one. primordial sound waves as a huge standard apparent size on the sky. This same concept But it turns out that the universe isn’t ruler to measure the properties of this explains why you can still judge distances slowing down at all. In 1998 two separate mysterious repulsive force. www.skyandtelescope.com.au 17 Seeing Cosmic Sound To minimise the exposure time, SDSS uses a method call multi-fibre spectroscopy. The image of the sky comes to a focus at the same location where the imaging detector sat, a 3-degree field of view that spans about 60-cm in diameter. In place of the imager, observers place an aluminium plate with holes drilled at the location of the objects of interest. Each hole is plugged with an optical fibre, a flexible glass tube several metres long and a little thicker than a human hair. Once the light enters the tip of the fibre, SPECTROSCOPY it is trapped inside the cylindrical walls and routed to PLATES the spectrograph. Fed by the fibres, the spectrograph Engineers drilled records a simple, two-dimensional picture with 1,000 holes into every aluminium hundreds of simultaneous spectra. plate used in the The original SDSS used 640 fibres, each covering BOSS survey, 3 arcseconds on the sky. For BOSS it was upgraded to oneholeforeach 1,000 fibres per plate, each capturing a field of view 2 observing target arcseconds across, and new technologies and optics in a given field of approximately doubled the instrument’s throughput. view. DAN LONG & THE SDSS COLLABORATION, WWW.SDSS.ORG Since each 3-degree window of sky has a different arrangement of galaxies, a new aluminium plate must be drilled to 10-micron precision. Workers plug in the optical fibers by hand at the mountaintop, taking roughly an hour to prepare each spectroscopic plate. On long, clear winter nights, SDSS has recorded as many as 9,000 spectra. SDSS astronomers rely principally on objects’ colour to decide which 1% of them should be pursued for spectroscopy. Galaxies vary in colour depending in part on their redshift; BOSS focused on 1.5 million galaxies whose extremely red colours mark them as giant, faraway elliptical galaxies. These galaxies are typically a million times fainter than the unaided eye can perceive. Plate after plate, night after night, and year after year, the survey built up to its full volume. With the release of the BOSS dataset in July 2014, roughly 2,500 plates had been drilled, plugged and observed, resulting in a total of 2.5 million spectra for 2.2 million unique targets. After SDSS collected the raw spectroscopic data, specialised software processed the output daily to produce final, calibrated spectra. The software then compared each galaxy’s spectrum to a wide range of reference spectra to determine its redshift and distance. Then the data were ready for further analysis. Sounds like cosmology The SDSS BOSS survey mapped out galaxies at MICHAEL SDSS / BLANTON several different redshifts, determined the size of the ‘ORANGE SPIDER’ SDSS has imaged the sky north (top) primordial sound waves at each redshift, and calculated and south (bottom) of the galactic plane. Light from Milky that redshift’s distance. The results provide the most Way stars has been removed, revealing the cosmic web. precise extragalactic distances ever measured. 18 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 2 Accelerating 1.5 Present time Decelerating Present size 1 Redshift = 0 0.5 Redshift = 1 LEAH TISCIONE; SOURCE: D. EISENSTEIN D. SOURCE: LEAH TISCIONE; Size of universe relative to present size S&T: –15 –10 –5 0 5 10 SDSS Time relative to present day (in billions of years) Combining galaxy maps with a detailed view of the without ever departing from its surface. FROM cosmic microwave background confirms a universe Similarly, we can compare the circumference of SPECTRA TO COSMOLOGY where normal and dark matter make up only 31% sound waves seen in the microwave background to the Left: Astronomer of the universe’s total energy. Dark energy takes up sound waves’ radius inferred from galaxy maps. We Anne-Marie theremaining69%anddrivestheever-increasing find that our 3D universe is indeed geometrically flat, Weijmans, who expansion of spacetime. in the same sense that a 2D sheet of paper is flat. is involved in a Thefactthatthesecomponentsaddupto100%is Comparing typical separations between galaxies recently launched the hallmark of a flat universe. In general relativity, over a range of redshifts further suggests that the project to map nearby galaxies, three-dimensional space can curve relative to our density of dark energy remains approximately constant plugs in bundles normal Cartesian expectations, with measurable over time. The measurements show that as the of optical fibres. effects. Cut a circle out of a piece of paper and it will universe doubles in size, the density of normal matter The fibres route haveacircumferenceequalto2π,or6.3,timesits drops by a factor of eight — but the density of dark incoming light to radius. But that rule doesn’t hold true for a circle energy drops by no more than a factor of 1.5. That the spectrograph. Right: Determining shaped onto the surface of a sphere. result agrees with predictions from the cosmological how redshift ConsiderEarth’scurved2Dsurface.Earth’s constant scenario, which suggests that dark energy relates to distance equatorformsacircleabout40,000kilometresin comes from the energy of empty space and therefore helps astronomers circumference. But flying from this curved circle’s remains constant in time and location. measure the centre (one of the poles) to its edge (the equator) covers Though BOSS results are in, SDSS is far from universe’s expansion. For just 10,000 kilometres. In other words, the ratio of finished. A recently launched project will continue example, in a thecurvedcircle’scircumferencetoitsradiusisjust through 2020, exploring the Milky Way’s history and universe whose 4, rather than 2π. By accurately measuring distances, dissecting nearby galaxies. Technological developments, expansion is we can determine that Earth’s exterior forms a sphere such as the introduction of tightly packed fibre bundles accelerating, light for spectroscopy, will aid these studies. from a galaxy at a redshift of 1 would But dark energy remains a powerful attractor r take a longer of our scientific attention, even as it pushes the time to arrive r universe apart. SDSS will keep mapping the cosmos, (travelling a longer S&T: distance) than GREGG DINDERMAN broadening its reach to farther regions of the universe. Using spectroscopy of faint galaxies and hundreds in a constantly expanding of thousands of quasars, the extended BOSS project universe. C = 2/r C = 4r will continue to refine our understanding of this most elusive component of our universe, the faint echoes of FLAT VS. CURVED Cut a circle out of a piece of paper the primordial sound waves. ✦ (left) and it will have a circumference equal to 2π multiplied by its radius. But for a circle shaped onto the surface of a Daniel Eisenstein is a professor of astronomy at Harvard sphere (right), the circumference is just 4 times its radius. This simple geometrical concept can be applied to determine University. He has been involved in SDSS since 1998 and whether our 3D universe is ‘flat’ or ‘curved’. served as the director of SDSS-III. www.skyandtelescope.com.au 19 Adaptive Optics ARTIFICIAL STARS Twin laser beams from the Keck telescopesatopMaunaKea,Hawai‘i,createartificialguidestars to aid adaptive optics observations of our galaxy’s centre. TA WEI WWW.ETHANTWEEDIE.COM / TWEEDIE ETHAN Untwinkling the Stars SHANNON HALL How did the world’s largest telescopes conquer the tempestuous atmosphere? hefirstfewdaysofanobservingruncanbe Macintosh (Stanford University) led the team that enchanting: the night sky so dark that familiar built the Gemini Planet Imager (GPI), the first in its Tconstellations are hard to find, the landscape class of next-generation adaptive optics instruments. typically barren and far from city lights, and the array The team had mounted GPI on the immense 8.1-metre of mirrors and instruments finally catching beams of Gemini South telescope, and the instrument would light from the distant universe. finally begin its planet search during this observing But on one such evening in November 2013, run. But it still had to go through an extended testing high in the remote Chilean Andes, Bruce Macintosh sequence, and Macintosh was finding the work tedious was bored. — he was anxious to ‘get on sky’. 20 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 So on the fourth night, after the team of engineers generation of AO-equipped mega-telescopes will push responsible for the tests headed to bed, Macintosh took the boundaries of sight even further. matters into his own hands. “That was the night where we said, ‘y’know, let’s just point it at a damn planet and Deep (and classified) roots see what it looks like.’” The team slewed the telescope Many early scientists, even Isaac Newton, wrestled toward Beta Pictoris, a star 63 light-years from Earth with with the problem of atmospheric distortion, but the a hot, young giant planet that orbits its star at almost twice real advances didn’t begin until the 1970s. That’s when the distance that Jupiter orbits the Sun. Then the Pentagon was working on something they waited — but not for long. Within 60 seemingly unrelated to astronomy: it seconds a lump had materialised on the needed a way to focus a laser beam on a screen before them. distant target, which meant protecting The same detection prior to GPI the beam from choppy wind. At would have taken an hour to image the same time, DARPA, an agency and days to process. Could the new within the Department of Defense, A D instrument capture an exoplanet A wanted to identify satellites N A in only a minute? The astronomers C launched by the Soviet Union. C R N filling the room remained skeptical. / Even at a good location, S I O R A They frantically grabbed their laptops M atmospheric turbulence smears out N IA T S and searched for any papers that might RI details smaller than 1 arcsecond across. H Y C G B show an image of the planet Beta Pictoris b. SSIN That’s good enough to see the cylinder- PROCE They then scrutinised the screens, holding their shaped Hubble, which is similar in size to most laptops sideways to better match the image’s orientation spy satellites, but not good enough to make out details. on the observatory’s computer screen. Sure enough, the The military needed a way to do better. images aligned. Before their eyes was a newborn gas If scientists could accurately measure how giant, seen more clearly than ever before. the atmosphere is moving, they could send that Spotting the exoplanet right off the bat was an information along to a flexible secondary (or incredible feat, says GPI chief scientist James Graham tertiary) mirror. In principle, this deformable mirror (University of California, Berkeley). “It doesn’t require would exactly cancel distortions introduced by any detailed analysis. It doesn’t require crunching the the atmosphere into the primary mirror’s image, numbers. It’s just completely evident in the raw data sculpting the rays of light (from a satellite or any other that an exoplanet is there.” target) back to near-perfect alignment. But the basis of GPI’s success was decades in the One of the first AO demonstrations was installed in making. Even 2,700 metres (8,900 feet) above sea level, 1980 on DARPA’s 1.6-metre telescope in Maui. It used Gemini South still sits beneath an ocean of air. So 168 piezoelectric actuators, which expand or contract the telescope uses adaptive optics (AO) to correct for in response to applied voltage, to very slightly bend a BETA PIC Top: the turbulent atmosphere. In GPI, more than 4,000 deformable mirror. Today, AO systems might contain One of the first actuators spaced just 400 microns apart deform the many thousands of these mirror movers, thanks to images the instrument’s secondary mirror to exactly match and improvements in their manufacturing, positioning Gemini Planet cancel out atmospheric distortion. Without AO, light and mounting. Imager took was from planets, stars, and galaxies would dance and of the disk around Beta Pictoris, a distort, like pebbles seen beneath a flowing stream. The star known to host colossal observatory wouldn’t see any sharper than a a planet. With backyard scope. But with AO, images steady themselves, just a minute- enabling astronomers to pick out fine details. long exposure, The technology that makes this feat possible was the newborn gas giant appeared born in the 1970s in classified government meetings. on screens in the A few select Air Force scientists and astronomers control room. worked together to design early versions of laser Left: The Gemini guide-star systems before the project was declassified Planet Imager’s in 1991. After several decades of innovation, AO is still first-light images brought elation improving with each new generation. Today, ground- to the team at based telescopes such as Gemini South can exceed the the Gemini South clarity of the Hubble Space Telescope. And the next GEMINI OBSERVATORY telescope in Chile. www.skyandtelescope.com.au 21 Adaptive Optics But even with the best deformable mirrors, Subject to be studied compensating for the atmosphere is no easy task. The simplest method calls for a star in the field of view, which would look like a small point if its light could travel undisturbed to the telescope. The atmosphere Artificial star introduces any extra blur. So keeping a telescopic eye dium layer So on the star gives a measure of atmospheric turbulence. But there’s a catch: in order to measure the rapidly changing atmosphere, astronomers need to catch a lot of photons quickly, so the star has to be pretty bright. No star fainter than 10th magnitude would do, and even if stars were evenly distributed, only 15 stars this bright would be found in each square-degree patch of the sky. This limitation wouldn’t be so bad if it weren’t for a second one: only a very tiny area of the sky around the star — up to about 30 arcseconds wide for images at near-infrared wavelengths — will have similar Atmospheric atmospheric turbulence. The two conditions leave only turbulence 1% of the sky available for AO observations. There had to be another way. So in the late spring of 1982, the military called on the Jasons — a group of scientists who meet once a year to give technical advice on issues of national security — to help solve the problem. In that classified think tank, scientists came up with a potential solution: shine a laser upward along a telescope’s axis and you can create Image distorted by atmosphere a bright artificial star wherever you like. With that in mind, Air Force scientist Robert Fugate and colleagues created a Rayleigh laser guide-star system at the Kirtland Air Force Base in Sodium Albuquerque, New Mexico. Molecules in the lower laser atmosphere such as oxygen, nitrogen and aerosols Telescope reflect the laser beam, creating a green-coloured spot Corrected of light in the sky. Fugate and his colleagues pointed Deformable image Camera mirror their system toward a pair of stars in Ursa Major, capturing an image 25 times clearer than previous work. The researchers were well on their way to conquering the age-old problem of turbulence. Wave sensor Declassifying AO But at the time fewer than 100 people in the world knew about it. Many Jasons spent years lobbying the military to take the wraps off, but it wasn’t until the HOW ADAPTIVE OPTICS WORKS As starlight Soviet Union fell apart (and spy satellites became less shines through the atmosphere, turbulent air distorts its of a threat) that the military considered declassifying wavefront. A blurry image results. In a laser guide-star AO system, a sodium laser shoots up to the mesosphere, the information. Scientists around the world had scattering among the sodium atoms there to create what started to catch up anyway — two French astronomers appears to be a bright yellow star. Computer algorithms published a paper describing the technique in 1985. measure this artificial star’s wavefront, which is similarly Finally, in 1991 Fugate was allowed to describe the jangled by the time it reaches the ground. The computer research at a meeting of the American Astronomical then deforms a flexible mirror to return both wavefronts to GREGG DINDERMAN their undisturbed forms. Society in Seattle, Washington. S&T: S&T: “Prior to that meeting I had never talked about this 22 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 with more than 10 people in the room,” Fugate recalls more than 20 years later. But by the start of his talk, the room had filled up with nearly 400 people, some of whom were standing three to five deep all around the walls. “I was as nervous as I could be,” Fugate says. But he did not disappoint. Utter silence followed his announcement, then noisy chatter filled the room. Although it was clear that adaptive optics was the tool astronomers needed, the current system was far from perfect. Take Fugate’s laser system. Because it used Rayleigh scattering in the lower atmosphere, itcouldonlyshineuptoabout20kilometresabove Earth’ssurface.Stillmoreairabovethislayerremained UNDERANOCEANOFAIR Despite its incredible seeing conditions, unmeasured. the Gemini South telescope pictured here still requires adaptive optics to So another Jason involved with the project, overcome the tempestuous atmosphere above it. Claire Max (then at Lawrence Livermore National GEMINI OBSERVATORY Laboratory), worked on a better solution: if a laser is tunedtoaspecificwavelength(589nanometers),it but could be tuned to sodium wavelengths. So one will excite a layer of neutral sodium atoms floating night Max set up a mirror to bounce the horizontal about90kilometresaboveEarth’ssurface.Initially laser beam up into the sky. She then pointed a deposited by meteors passing through the atmosphere, small telescope at the guide star and measured the thesesodiumatomswillfluoresceinresponsetothe atmosphere’s disturbances. It was proof that she could laser’slight—aneffectvisiblefromtheground. improve upon Fugate’s existing system, and by 1996 Bytheearly1990safewsodiumlasershadbeen Max and colleagues had deployed a prototype at Lick built,butnonepowerfulenoughtodothejob.Itwas Observatory’s 3-metre telescope. But even then most overlunchonedaythatMaxandacolleaguerealised observatories failed to embrace the technology — it thenecessarylaserwassittingbeneaththeirfeet. was too expensive. LivermoreLaboratoryhadanenormousunderground In 1999 a US$20 million grant from the National laser that was normally used to separate isotopes Science Foundation kick-started the Center for GREEN VS. YELLOW Green-tinted Rayleigh lasers, such as the ones being installed at the Large Binocular Telescope (left), are commercially available and therefore cheaper. They reflect off a lower layer of the atmosphere and account for distortion nearer the ground. Lasers tuned to 589 nanometers, such as the one employed by the Gemini South telescope (right), reflect off the higher- altitude sodium layer about 90 kilometres GEMINI OBSERVATORY GEMINI JULIAN ZIEGLEDER / MAX PLANCK INSTITUTE FOR EXTRATERRESTRIAL PHYSICS above the ground. www.skyandtelescope.com.au 23 Adaptive Optics Adaptive Optics. Astronomers from the University of California and Livermore continue to work together to improve upon existing technology and further develop the techniques necessary to use it. Now, even though laser-assisted AO systems still have to be custom-built for every observatory, most large telescopes have joined the game. Outshining Hubble BEFORE AND AFTER Without adaptive optics, a near-infrared image In optics the motto is generally, “the bigger, the of Uranus appears blurry (left). When the same image is taken with AO better.” A larger primary mirror captures more technology (right), the faint and fuzzy ring resolves into several distinct rings, photons and enables astronomers to see fainter and and small storms within the atmosphere are revealed. HEIDI B. HAMMEL AND IMKE DE PATER / WMKO farther objects. It also determines the level of detail the telescope can pick out, as long as atmosphere isn’t an issue. The Hubble’s 2.4-metre mirror can resolve objects 0.1 arcsecond apart at 1 micron, but Adaptive t 5 Optics OFF only because it flies abou 60 kilometres above Earth’s surface. With the advent of adaptive optics, TUNING IN one of Keck’s 10-metre telescopes (among the largest TO SGR A* observatories in the world) can resolve details as fine Astronomers used as 0.04 arcsecond — producing images more than complex techniques twice as crisp as Hubble’s. to reveal action in In 1999, the Keck Observatory placed its first our galaxy’s centre natural guide-star system on Keck II and a year before adaptive optics (top). later on Keck I. With better deformable mirrors and With the advent even the ability to separate light into its constituent of AO (bottom), wavelengths, this system was radically improved in () () astronomers comparison to earlier AO counterparts. have pinpointed Adaptive Such razor-sharp vision enabled astronomers to and tracked the Optics ON minute motions of peer into the crowded environment at the centre of individual stars as the Milky Way Galaxy. Before getting access to Keck’s they careen around adaptive optics, Andrea Ghez (University of California, Sgr A*, our galaxy’s Los Angeles) and her team had used a camera that took supermassive black exposures every few milliseconds to create stacked hole. The larger square fields are images of this region. But from 1995 to the present day, 6″ on a side, insets Ghez’s team has been able to watch stars orbiting the span 1″, and all Milky Way’s centre at closer distances than ever before. images were taken at These previously hidden stars whip as close as 45 wavelengths near 2.2 astronomical units to the centre, at speeds up to 12,000 microns. kilometres per second (roughly 4% the speed of light). UCLA GALACTIC CENTER GROUP / W.M. KECK OBSERVATORY LASER TEAM Yet the centre appears empty. The source of gravity that’s flinging the stars in their speedy orbits can’t be anything but a supermassive black hole. Although Ghez herself is modest about this achievement, other astronomers think her research is without a doubt the best example of AO’s successes. “I don’t have words to express how stunning that is,” NASA;M.CHUN/NICITEAM T.NAKAJIMA/S.DURRANCE;S. KULKARNI/D.GOLIMOWSKI/ says GPI’s Macintosh. “It’s both just visually stunning ADAPTIVE OPTICS REVOLUTION The AO-enabled Palomar Observatory to watch as a human, and scientifically it’s really, really discovered the first brown dwarf, Gliese 229B, tucked within the glare of its important.” companion star (left). Hubble followed up a year later (centre) to help pin down its orbit. After a decade, an image captured by the Near-Infrared Coronagraph and AO Then in 2003, Keck II upgraded its AO system system on the Gemini North telescope (right, in a slightly larger field of view) shows to use a sodium laser sent from Max’s team at how far the technology has come. Livermore (Keck I followed suit a few years later). Peter 24 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 Wizinowich, who leads AO development at Keck, has Star spent the past two decades improving the technology. He has commissioned new lasers, better deformable Artificial mirrors, and faster code to work seamlessly between guide star the two. As such, Keck’s AO system is the most productive one in astrophysics: to date, it’s responsible for roughly 70% of refereed-science papers that use adaptive optics. Deformable Orbits seem to be the theme of Keck’s first AO secondary mirror results. A couple years after Ghez’s work, a team including Macintosh used the Keck II and Gemini North telescopes to directly image three pinpricks of infrared light around HR 8799, a 6th-magnitude star in the constellation Pegasus. In theory such direct Primary mirror images of exoplanets could reveal their composition, Beam splitter Beam splitter climate and even possibilities for life. Though this first image wasn’t yet up to that task, the discovery laid the GREGG DINDERMAN Computer Camera Computer Camera groundwork for direct-imaging systems. S&T: The next generation: megascopes Even space-based telescopes will one day utilise a TO INFINITY But the most expensive and ambitious spree of form of adaptive optics. Though they fly high above A laser guide star telescopes — and their accompanying adaptive optics the atmosphere, their AO will correct imperfections shines down from a layer in Earth’s — has only just begun. Giant observatories currently in the optics themselves. Hubble, for example, slips atmosphere — a under development include the Thirty Meter Telescope between day and night roughly every 45 minutes. This lot closer than on Mauna Kea, the European Extremely Large change warms and cools the spacecraft and changes real stars, which Telescope in Chile, and the Giant Magellan Telescope its focus. Although the beloved space telescope might as well also in Chile. doesn’t have AO, its successor, the James Webb Space be infinitely far away. As a result, When it comes to building billion-dollar Telescope, will launch with a built-in AO system. artificial starlight behemoths, adaptive optics is a must. Increasing shines down the size of these telescopes’ primary mirrors would Stumbling blocks in a cone (left), mean nothing if the atmosphere were to limit It’s safe to say that laser adaptive optics has rather than in their resolution to 1 arcsecond. But cancel out the revolutionised astronomy, but it does present several the cylindrical shape of real atmosphere, and a 30-metre telescope could spot observing challenges. Contrary to popular belief, starlight (right). objects as small as 0.008 arcsecond across. artificial laser guide stars don’t allow astronomers to So atmospheric Megascopes will need improvements in laser see any celestial object on any clear night of the year. turbulence won’t technology if they’re to implement AO. While the light Astronomers still need a second (real) guide star — affect light from from a star infinitely far away will fall through the albeit very faint — to make a few basic corrections. With an artificial star in the exact same atmosphere in a cylinder — its rays of light perfectly this restriction, laser guide-star AO currently covers way as light from parallel — a sodium laser guide star’s light falls 70% of the sky, largely in the galactic plane where there a real star. Future through a tall cone that peaks at the sodium layer. are more stars. AO systems will Since its rays aren’t perfectly parallel, a single sodium Also, sodium beacons don’t work perfectly every use multiple laser guide star can’t perfectly mimic a star. The larger the day of the year. The blanket of sodium in the upper beams to correct for turbulence telescope, the more that difference begins to matter. atmosphere thickens every time Earth tumbles into a within a larger “The 30-metre telescopes are going to require stream of meteors. So the sodium layer will be densest area of the sky. not a single laser but a grid of laser beacons, each September through December, after the brightest of them with their own cone, to try to reconstruct meteor showers of the year (namely the Perseids, the atmospheric turbulence in three dimensions,” Geminids and Orionids) deliver their bits of sodium. Macintosh says. Demonstration systems have been Unfortunately, this is when the weather is often deployed at the Gemini South telescope and the Very poorer for many telescopes (particularly Northern Large Telescope. A similar system is being readied Hemisphere ones). During the optimum observing for the Keck II telescope. Ghez can’t wait because she conditions of summer, astronomers may struggle to expects to see 10 times the number of stars in the produce a bright-enough beacon of light. galactic centre as she’s seen before. Finally, there’s one more minor — and sometimes www.skyandtelescope.com.au 25 Adaptive Optics THE FUTURE OF AO This artist’s concep- tion shows multiple lasers being deployed as part of the adaptive optics system planned for the European Extremely Large Telescope, which is currently under construction on Cerro Armazones in Chile. ) (SKYSURVEY.ORG ESO / L. CALÇADA / N. RISINGER amusing—issue:localaviation.“Smallprivateplanes So,shortlyaftertheSunsets,mostofthebiggest arelikemoths,”saysMarshallPerrin(SpaceTelescope opticaltelescopesaroundtheworldbeginthenight’s ScienceInstitute).“They’redrawntothelight.”When observationsbyfiringoutalaserbeamthecolour Perrin was at Lick Observatory over a decade ago, his of sodium street lamps. The laser itself can be seen teamwouldn’toperatethelaseruntil11p.m.,when from several kilometres away, an eerie beam in the most of the general aviation was done. So-called encompassing darkness. ‘aircraft spotters’ still work today at the largest Fugate likes to look at it philosophically. “We’re telescopes to search for planes. using the remnants of our Solar System — these Becauseoftheselimitationssomeastronomers meteors — as a mechanism to investigate the edge prefer using bright stars where available. Macintosh oftheuniverse,”hesays.“Imean,it’sjustamazing andhiscolleagues,forexample,onlysearchforyoung when you think about how it all kind of comes planets near relatively close stars, side-stepping any together that way.” ✦ issues with artificial guide stars. But not everyone isasluckyasMacintosh’steam.Forthosewhodon’t As a freelance science journalist, Shannon Hall spends haveabrightstarhandy,anartificialbeacon,albeitan herdaysponderingthewondersoftheuniversefroma imperfect one, opens a new window into the universe. local coffee shop. AO Spin-offs The quest for the perfect image doesn’t stop with astronomy. Adaptive optics has also been applied to other fields — even the military. Microscopy: Biological samples bend a Ophthalmology: Ophthalmologists struggle Military: It took more than 25 years, but microscope’s beam of light in unpredictable to see past the fluid inside the eye to make it seems the military’s goal to utilise laser ways. By first focusing the light into a glowing out minute details in the retina. But with weapons has finally left the realm of science point, scientists can see how it warps as adaptive optics, they’re able to see the finer fiction. Engineers can now pre-distort a laser it passes through intervening tissues and features, allowing them to diagnose potential beam to cancel out atmospheric turbulence correct for the distortion. eye diseases early enough to prevent them. and focus with precision on a target. 26 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 Mercury Transit Anom a loTHOMAS DOBBINS s Appearances Will modern observations of the Mercury ESPENAK FRED transit stack up to the historical record? mateur astronomers in certain parts of the Mercury that many anomalous appearances have been globe are making preparations to observe the reported over the years. AMay 9 transit of Mercury, which will be visible These oddities have long been the subject in its entirety from eastern North America, most of of speculation and even heated debate. Many South America, western and northern Europe and astronomers have tried to explain the mysterious north Africa. Others in western North America, most ‘black-drop effect’ frequently seen when Mercury’s of Africa and almost all of Eurasia will see at least disc touches the inner edge of the Sun at second part of the transt. Alas, observers in Australasia will contact (near the beginning of a transit) or at third completely miss out on this event. contact (near the end of a transit). But other strange Passages of the tiny planet across the face of the visual effects have sparked interest as well. For Sun have never stirred as much popular interest as example, the anomalies observed during the Mercury the far rarer transits of Venus, those spectacular transit on November 5, 1868, were the subject of a events that have inspired expeditions to far-flung detailed account in the Monthly Notices of the Royal corners of the globe for several centuries. However, Astronomical Society written by the celebrated British sufficient attention has been paid to transits of amateur astronomer William Huggins, who is 28 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 chiefly remembered today for using a spectroscope to determine the chemical composition of stars and nebulae. A wealthy dealer in silks and linen with a keen interest in the sciences, Huggins used the proceeds from the sale of his family’s lucrative textile business to build a well-equipped observatory on Upper Tulse Hill in south London. Its centrepiece was a telescope that would still be the envy of most amateur astronomers a century and a half later — a 20-cm refractor featuring a superb objective lens made : LEAH TISCIONE by the renowned American optician Alvan Clark. S&T Huggins enjoyed decent daytime seeing during the November 1868 transit. “The Sun’s edge was a little CLEARLY VISIBLE tremulous from atmospheric agitation,” he recounted : LEAH TISCIONE British S&T observer in his notes, “but the solar surface was so well defined V. A. Firsoff thatthebrightgranulesofwhichitiscomposedcould detected a narrow be distinctly seen.” surrounding Mercury. Most, however, compared it to but brilliant Shortly after the entire disc of Mercury was the bright band bordering the limb of the airless Moon ring around silhouetted against the brilliant backdrop of the Sun’s thathadbeenreportedduringthepartialphasesof Mercury during the November surface,Hugginsnoticedanevenbrighter,sharp- solar eclipses, a phenomenon that Astronomer Royal 7, 1960, transit. edged halo surrounding the black dot: GeorgeBiddellAiryhaddismissedin1864as“strictly He projected the an ocular nervous phenomenon.” In the 1881 edition solar image from The breadth of the luminous annulus was of his classic observing handbook Celestial Objects for a 16.5-cm reflector Common Telescopes, the Reverend Thomas William onto a piece of about one-third of the planet’s apparent white cardboard. diameter.Theaureoladidnotfadeoffat Webb wrote off the halos as “deceptions from the LUMINOUS the outer margin, but remained of about violentcontrastandthefatigueoftheeye.”Tothe French astronomer Camille Flammarion, they called ANNULUS thesameintensitythroughout,witha to mind the illusory bright aura that he repeatedly saw British astrono- definedboundary.Theaureolawasnot surrounding the shadow cast by a hot air balloon onto mer William sensiblycoloured,andwasonlytobe Huggins reported sunlit prairies during his many ascents. a bright halo distinguishedfromthesolarsurfacebya The halo is a striking example of a phenomenon first surrounding the very small increase of brilliancy. described by the Austrian physicist Ernst Mach in 1865. disc of Mercury Mach noted that the eye-brain combination invariably and a luminous There were a few corroborating observations of the exaggerates contrasts at the borders of adjacent extended spot on the planet during the transit bright halo surrounding miniscule Mercury that surfaces of differing brightness. Observational of November 5, day. Observing with the 32-cm refractor at the Royal astronomy is rife with examples of these ‘Mach bands,’ 1868. Observatory at Greenwich, E. J. Stone reported: “With notably the ‘Terby White Spot,’ a spurious bright feature power 137, a ring of light was clearly visible around the often seen bordering the intensely black shadow cast by disc of Mercury. It extended to a distance of nearly a Saturn’s globe across the planet’s rings. semi-diameter.” But scores of other observers failed to But in addition to the bright halo, Huggins see any trace of the halo, and even Stone was cautiously witnessed an even more curious phenomenon: skeptical, writing: “I am of the opinion that it arose from mere contrast.” AlmostatthesamemomentthatIfirst Similar effects had been reported for more than perceived the surrounding annulus of light, I a century. First described by the French astronomer noticedapointoflightnearlyinthecentre François de Plantade in 1736, the luminous ring oftheplanet.Thisspothadnosensible was documented again by his countryman Honoré diameter with the powers employed [120 Flaugergues during the transits of 1786, 1789 and × 1799. To the German astronomer Johann Hieronymus and 240×],butappearedasaluminous Schröter, the halo was a pale, almost ghostly, object that point… I kept it steadily in view until that was “scarcely brighter than the surface of the Sun.” part of the planetary disc, where the point A few observers interpreted the halo as sunlight of light was situated reached the Sun’s limb, refracted by a dense, distended atmosphere I then ceased to see it. www.skyandtelescope.com.au 29 Mercury Transit Like the bright halo, points of light and diffuse bright skill and experience, and equipped with telescopes patches were frequently reported during transit events. of comparable size and quality, saw nothing unusual Most dispatches described features that were centrally while their colleagues were reporting these curious located, although in some instances they were offset appearances was certainly troubling, and a matter towards the edge of the planet’s tiny black disc. of much discussion. Suggestions that erupting The fact that a host of observers, generally of equal volcanoes or intense auroral displays might account for lights rivaling the solar photosphere in brightness were deservedly taken with a grain of salt. Far more plausible were the explanations involving internal ‘ghost’ reflections from the surfaces of the telescopes’ objective and eyepiece lenses, which lacked modern antireflection coatings. In 1850, the Reverend Baden Powell, Professor of Geometry at Oxford University and father of the founder of the Boy Scouts, suggested that optical diffraction was responsible. Eighty years later the French astronomer and optician André Couder was able to reproduce the luminous spot in his laboratory at Meudon Observatory in Paris. While photographing black circles projected against a brilliant background, Couder was able to record the bulls-eye pattern of the bright Airy disc at the centre of the circle, surrounded by faint diffraction rings. A slight misalignment of the optical elements displaced the spot toward the edge of the circle. Even with perfectly aligned lenses, when the background was not uniformly illuminated (to mimic the darkening that occurs near the limb of the Sun), the spot was not concentric. Despite Couder’s convincing experiments, more than mere optical effects seemed to be at play. Observing the November 8, 1881, transit of Mercury through a 120-mm refractor equipped with a Herschel wedge at the Sydney Observatory, Australian astronomer Lawrence Hargrave saw a central bright spot very distinctly three minutes after ingress. However, he soon realised that it would disappear ‘on looking steadily at it’. Reports such as Hargrave’s led the late William Corliss, who compiled several catalogues of astronomical anomalies, to conclude that “something akin to those optical illusions where grey images appear out of nowhere amid geometrical designs” might be involved. The upcoming transit of Mercury will be an opportunity to glimpse these strange, elusive anomalies once again. The knowledge that they’re strictly in the eye of the beholder shouldn’t rob them entirely of the ability to evoke a sense of wonder. Through them, we’re visually connected to our observing forebears. ✦ Contributing Editor Thomas A. Dobbins has observed WORKING FROM HOME Huggins poses inside his observatory at Upper Tulse most reported phenomena on the planets, both real Hill next to the 20-cm Clark refractor kitted out for spectroscopic observations. OFCOURTESY THE SCIENTIFIC WILLIAM OF PAPERS HUGGINS and illusory. 30 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 NGC 5367 imaged with ProLine PL16803. Image courtesy of Wolfgang Promper. Widest Field DQG Highest Resolution: Introducing our 50 Megapixel ML50100 70 KAF-50100 with microlens The world’s first KAF-50100 sensor with microlenses is the result of a year-long 60 collaborative effort between ON Semiconductor (formerly Kodak) and Finger Lakes KAF-50100 without Microlens 50 Instrumentation. Our goal: to create a sensor with both high resolution and excellent quantum efficiency (QE). The significantly boosted QE of our new 40 ML50100 with microlens technology makes it as sensitive as the popular 30 KAF-16803 detector, but with 3X higher spatial resolution. The ML50100 is the 20 ideal camera for wide field imaging with shorter focal length telescopes. 10 Absolute Quantum Efficiency Absolute Quantum At Finger Lakes Instrumentation, we design and build unrivaled cameras, filter 0 360 420 480 540 600 660 720 780 840 900 960 1020 wheels, and focusers to pave your way to success—whichever path you choose. Designed and manufactured in New York, USA. Wavelength (nm) Significant Increase in Sensitivity TM ML50100: For more information, visit 8136 x 6132 www.flicamera.com/51.html 6 micron pixels MADE IN USA 3X more resolution than the ML16803 Finger Lakes Instrumentation 1/3 more area than the ML16803 © 2015 Finger Lakes Instrumentation, Inc. All rights reserved. Celestial Imaging MANY CHOICES With so many cameras to choose from today, how can beginners decide which one best suits their needs? ALL PHOTOS BY THE AUTHOR RICHARD S. WRIGHT, JR. Choosing a camera for astrophotography The question isn’t which is best, but which is best for your goals. here’s never been a better time to take up technology can be bewildering to the newcomer. astrophotography. A good amateur image This article isn’t about which camera to buy, Ttoday would have been award-winning and but rather attempts to explain the buzzwords and groundbreaking only 10 years ago, and a half performance metrics used to evaluate camera models centuryagonoonewouldhavebelieveditwasareal today. There’s no such thing as the ‘best camera’ on the photograph — because even shots from professional market. The real best camera is constrained not only observatories were inferior. Advances in optics, by your budget but also by your imaging goals (what mounts and cameras have all contributed to the you intend to shoot) and which optics you’ll be pairing golden age of imaging we live in today, but the it with. Matching a camera to your glass is just as 32 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 important as other criteria when choosing a camera. So an inherent sensitivity to light. A chip that’s not very let’s have a closer look. sensitive would have less than stellar performance with a slow focal-ratio system. Telescopes 101 Two things measure the light sensitivity of an Although most people associate a telescope with imaging sensor. The first is quantum efficiency, or the concept of magnification, the main purpose of a QE, which simply conveys how efficiently the chip telescope or camera lens is actually to gather light. converts photons into electrons. A detector with a The bigger the opening, or aperture, the more light QE of 100% would turn every single photon received can come in. This is the first principle of photography into an electronic signal. On the other hand, a QE of — no matter which camera you choose, more light is 50%, which is typical for a consumer-grade detector, always a good thing. converts only half of the light reaching it into an Regardless of whether we’re talking about electronic signal. a camera lens, refractor telescope, reflector or A detector’s QE is not the entire story — the catadioptric, we measure an optics’ ability to collect size of its pixels is also very important. Large pixels light by its aperture. This is simply how wide the have more surface area for collecting photons front opening is that lets in the light (or the size of and converting them into electrons (which are your primary mirror). subsequently read out as your image). Additionally, Magnification is determined by your optics’ focal the size of a pixel is figuratively the size of the bucket length. Less magnification makes the image smaller that holds electrons generated by the light. So a bigger but brighter. Think of light as sand pouring out of a pixel holds more electrons and has a larger surface bag. In 5 minutes of exposure time you only get so area for collecting them. Today’s race to achieve ever- much sand, and you can make a big, wide, but thin smaller pixels is a race toward doom when it comes pile of sand, or a small but deep pile of sand. Deep to low-light photography. However, this isn’t to say piles of sand (more light) produce brighter images and you should always avoid small pixels, as is the case in an improved signal-to-noise ratio. If you want a wide planetary video cameras. and deep pile of sand, you have to expose longer or get Another important factor with pixel size is what’s a bigger aperture with the same focal length. known as the full-well capacity. This specifies how The next important metric in understanding a many electrons each pixel can hold. A camera with telescope or lens is its focal ratio, usually indicated by small pixels might have a full-well capacity of 10,000 the designation f/ and a number. This is determined ADU (analogue-to-digital units — how many electrons by dividing the optical system’s focal length by its can be registered), while a larger pixel might have aperture. The focal ratio is a geometric indicator of one of 100,000. In addition to the effective sensitivity, how much light is delivered to the detector (be it a this affects the dynamic range. Do you want to record digital sensor or your eyeball) per unit area of the bright stars and faint galaxies or nebulae in the same focused image, and a key point when selecting a exposure without saturating? You need a large full- camera later. Optics are called ‘fast’ if the focal ratio is well capacity for this. about f/5 or lower or ‘slow’ if it’s f/7 or higher. Where to draw the line between fast and slow optics is Read noise somewhat subjective, but the key takeaway is that fast Read noise is one more important metric to consider optics deliver more photons per pixel. for getting good images with any digital camera. One interesting consequence of this is that an This is noise introduced by the process of reading the image of, say, the Horsehead Nebula will be just as image off the chip. The key to pulling faint details out ‘bright’ with an 80-mm aperture at f/4 as it would of deep sky images of nebulae, galaxies and comets is be with a 300-mm f/4 setup. The focal ratio is the getting those details to register higher than the read unifying factor, and it works across all optics as a noise from your camera. While you can stack many concrete metric of how long you’ll need to expose for a shorter exposures to get an effectively longer exposure, target signal per pixel for a given subject. you can’t pull out faint details unless those details are above the read noise. No amount of stacking will Pixel performance rescue them. So how does all this apply to camera selection? The detectors in digital cameras, regardless of whether Cooled CCD or DSLR? they are CCD (charge-coupled device) or CMOS Here’s something that perplexes many beginners: (complementary metal-oxide semiconductor), each have astronomical deep sky CCD cameras always include www.skyandtelescope.com.au 33 Celestial Imaging IMPROVING TECHNOLOGY Today’s digital cameras and high-quality commercial optics enable amateurs to produce images that were simply unimaginable a few decades ago. This deep image of M45, the Pleiades (left), was captured with a 200-mm-aperture telescope and Canon 5D DSLR camera. Compare that to the photo above, shot on film with the 60-inch reflector at Mount Wilson Observatory in 1995 — considered a good result at the time. some form of cooling of the sensor, yet DSLR cameras Colour or mono? (andthemajorityofplanetaryvideocameras)donot. Colour chips are really the same as monochrome chips, Why is that? First, understand that cooling a chip does with the only difference being that they’re topped by a notmakeitmoresensitive.Coolingreducesthermal thin, multi-coloured layer called a Bayer filter. This is a noise, which is where heat ‘jiggles’ loose electrons, and grid of microscopic filters with one red, green or blue makes them register as light signal in your sensor. filter (in a ratio of 25%, 50% and 25%, respectively) CATCHING You can reduce this somewhat with what’s called dark over each pixel on the detector. The sensor still records PHOTONS frame calibration, but a dark frame (taken with no a monochrome image, but it’s then processed with The pixels in light striking the detector) also has thermal noise. So interpolation algorithms to create a full-resolution your camera can the cooler the chip is when exposing, the less thermal colour image. be thought as buckets; small noise is generated. Commercial DSLR cameras do not There are advantages to adopting a colour workflow pixels capture include cooling because they weren’t designed to make versus the monochrome/filtered workflow in astro- fewer photons the extremely long exposures required for deep sky imaging, but one factor to consider is that the Bayer than large ones, astrophotography. matrix reduces the effective QE of the chip. For and will fill up In general, a cooled camera will give you much example, ‘red’ pixels do not receive 100% of the red (saturate) much faster than a cleaner (less noisy) images than an uncooled camera light because of the Bayer filter, and so the base QE sensor with can. While the gain from uncooled to cooled is huge, is effectively reduced. The QE of colour sensors is large pixels. thebenefitofdeepcoolingdoesstarttodropoffafter generally much lower than that for monochrome abit.Thegaingoingfrom20°Cto30°Cbelow detectors, so the former work best with fast focal the ambient temperature is not as great ratios. You might have to work very hard to get good as the initial drop to reach 20°Cbelow results from most DSLRs with f/10 optics on deep sky ambient. So don’t lose any sleep if objects, compared to using a monochrome detector getting that extra –10° is going to break matched with high-efficiency colour filters. your budget. Some of the newer imaging chips Determine your goal (particularly those produced by Sony) do An obvious consideration when contemplating a not require dark frame calibration at all. camera purchase is what you want to shoot with that They’re rated as having extraordinarily camera. For imaging the planets, Sun and Moon, the low thermal signal after some moderate hands-down winners these days are the CMOS-based cooling, often as little as one electron over video cameras. The biggest advantage of modern a period of a lengthy exposure! Such a CMOS chips is the readout speed, critical to the small thermal signal creates negligible planetary imaging technique of recording large video S&T: LEAH TISCIONE noise, so this is a significant advantage. streams and stacking the sharpest frames. However, 34 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 RAW data RGB output Read RR RRRR RRRR Bayer RR De-Bayering RRRR filter array process RRRR GG GGGG GG Interpolation GGGG GG algorithm GGGG GG GGGG BBBB BB BBBB BBBB LEAH TISCIONE BB BBBB S&T: super-fastreadoutspeedsaren’twarrantedunlessyou COLOUR OR MONOCHROME Colour imaging sensors are actually have optics that can deliver enough light to the sensor monochrome chips with tiny colour filters placed over each pixel (left). A special —nottomentionacomputerthatcanhandlehigh computerprogramknownasadebayerfilterseparatestheindividuallyfiltered pixels into their respective colour channels (centre), and then fills in the missing data transfer speeds. pixels in each colour using an interpolation algorithm to create the final colour The choice of monochrome versus colour in result (right). Colour sensors have lower efficiencies, so they generally work best planetary photography is still an important decision. with fast optics. Monochrome cameras will generally be more sensitive,allowingshorterexposuresandfaster shutterspeeds.Andtheyarethebestforlunar andsolarimaging,whichinvolvetargetsthatare essentially monochrome. Thedecisionisn’tasstraightforwardwhenshooting the planets. Imagers regularly get phenomenal results using colour cameras. Monochrome cameras with afilterwheelcompromiseyourproductivity,inthat you’ll have to change filters, process three different videostreams,andthencombinetheresultsintoa ZOOMING singleRGBimagelater.Evenso,thisistherouteto While the focal the very best data you can get out of your system. And length of an optic monochrome cameras are a better choice if you intend will determine toshoottheplanetsusingspecialisedfilterssuch the magnification asthosethatisolateultraviolet,methaneorinfrared of your target, the focal ratio wavelengths. determines the Ifyourgoalisdeepskyimaging,you’llwanta brightness of the larger chip (to record more of the sky) than most image. This shot video cameras provide. You can use a planetarium of the Horsehead program such as TheSkyX (bisque.com)tosimulate Nebula (top) was recorded with thefieldofviewofyourpotentialoptics-camera a 300-mm lens combination. (Full disclosure: I work for Software at f/4, while the Bisque.) Experiment with the field of view of your bottom photo was telescopes or lenses to see if you can fit the objects you with a 105-mm wanttoimageintheframeofyourdesiredcamera.Is refractor at f/4.5, producing a nearly theobjectatinyfeatureinthemiddleofalargefield equivalent signal ofstars,orwillyouneedtomosaicmultipleimages per pixel with together to cover the entire object? higher resolution. www.skyandtelescope.com.au 35 Celestial Imaging COMPUTER RESEARCH Planetarium software that includes field-of- view indicators for specific imaging detectors and telescope combinations can help you decide which type of astrophotography works best with the optics you already own. If you are primarily limited to light-polluted skies, In addition, the signal from deep sky fuzzy objects agoodchoicefordeepskyimagingisamonochrome needs to be as high above the skyglow as possible, camera equipped with narrowband filters. which means taking very long exposures that tend to When imaging through narrowband filters, there saturate small pixels. arefewdrawbacksforlivingsomewherewithoutdark PROPER skies. You can even image during the bright phases Image sampling SAMPLING oftheMoonwhenmost‘natural’colourimagersare Finally, let’s talk about sampling. Any optical system, Matching your outofbusiness.Butthereissomepenaltytoshooting whether it’s a telescope or a camera lens, has an pixel size to your with narrowband filters. They block more light than intrinsic resolving capability limited by diffraction optics, known as broadband filters and require much longer exposures (a physical limitation we can’t beat). The smallest sampling, is an toachieveacomparablesignal,sodon’ttrythisifyou focused spot is called the Airy disk, which depends on important factor in achieving a havehighf/ratioopticsoramountthatcan’treliably the wavelength of light and the aperture of the optical great astrophoto. guide for more than a few minutes. system. Larger apertures have smaller Airy disks An undersampled Anotherboonforlight-pollutedskiesisdeep (sometimes called the spot size) and can theoretically image (left) will full-well capacity detectors. To get images from a deliver higher-resolution images. However, in most appear pixelated light-polluted sky nearly as good as those taken from cases, the best resolution you can obtain is limited by when zoomed in. Oversampling, adarksky,youhavetoimagemuchlonger.Oneof atmospheric turbulence, commonly called ‘seeing’. caused by using a the primary impediments here is the skyglow, which Small pixels are better suited than large ones to long focal-length adds considerable background signal to your images. take advantage of a fast optical system. Conversely, a telescope and a camera with small pixels (middle), often results in fuzzy images, particularly when the atmosphere is turbulent. A properly sampled image (right) avoids both of these issues. 36 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 slow optical system would probably waste the potential resolution gain provided by smaller pixels (as well as having the disadvantage that less light is delivered to each small pixel). In an undersampled image, there are too few pixels for the detail the optics and sky conditions could have delivered. Conversely, oversampling means you’re using far too many pixels given the resolution capabilities of your optics or the sky conditions. A super-high-resolution camera will not really deliver more resolution than your optical system or the local seeing conditions can deliver; you just get a blurry mess that looks better only when you shrink it down in Photoshop. Better results are obtained with proper sampling in the first place. You can easily determine your sampling resolution with this formula: arcsec/ pixel = 206.3 × pixel size / focal length (mm). Typical ‘average’ seeing is about 2 arcseconds. Parting thoughts Selecting a camera for astrophotography shouldn’t be done outside the context of the optics you’ll use it with. In general, cameras with small pixels or colour detectors perform well when paired with fast focal- ratio instruments. While you can certainly use a camera with big pixels on a fast optical system (which compensates for a lower QE detector and less-than- perfect guiding), they also perform very well on slower optics. In addition to a camera chip’s sensitivity, read noise is the limiting factor when stacking short exposures to reveal faint detail in deep sky objects. Cooling provides a huge boost in performance, but don’t obsess over really deep cooling if you’re just getting started. Finally, I’ve intentionally neglected to address the debate over CCD versus CMOS sensors. That’s because there really is no debate, given the current state of the art. Both deliver great images and perform very well for astrophotography. CMOS has a definite edge in readout speed (great for video), while CCDs are more sensitive to ultraviolet and infrared wavelengths, though this won’t be the case much longer. For normal deep sky photography I would not let the choice of a CCD or CMOS detector be a deciding factor when UNDERSAMPLING BENEFITS choosing between two similar cameras. A DSLR with a wide-angle lens Just remember, there is no single ‘best camera’. vastly undersamples the night Consider what you want to image, where you’re sky, but is relatively unaffected imaging from and how you’re collecting the light. by atmospheric turbulence and Using these criteria, you can evaluate a camera’s tracking errors. This image was specifications and suitability to your imaging goals. ✦ taken with a simple sky tracker (Sky-Watcher Star Adventurer) and a Canon EOS 5D DSLR with a Richard S. Wright, Jr. is a senior software developer at 14-mm f/2.8 lens. Software Bisque by day and an astrophotographer by night. www.skyandtelescope.com.au 37 Lunar imaging our nearest neighbour, the Moon. It’s not quite as easy as just walking up to the eyepiece and snapping away — but that’s the general idea. Whether you have a smartphone or tablet (which usually have small, fixed-focus lenses) or a much more versatile compact camera or DSLR, all employ a similar set of operational modes. Some have a ‘manual’ setting, and that’s preferable to the ‘automatic’ mode, which tends to overexpose lunar images. Apps like NightCap Pro can add these features to your smartphone. Using the manual Shoot setting, you can adjust the shutter speed, exposure, the aperture and ISO (or at least your phone’s brightness setting) to control the amount of light reaching the camera’s detector. A fast shutter speed helps minimise blurriness due to atmospheric turbulence, wind, a nontracking mount or an unsteady hand holding the Moon camera up to the eyepiece. with a smartphone Perhaps the most important setting is ISO. Basically, the higher the ISO value, the greater the detector’s sensitivity to light. Typical smartphones or compact cameras have an ISO range of 100 to 1600, while new ‘low-light’ models can reach 6400, 12,800 or higher. The tradeoff is that higher ISOs add more noise or ‘graininess’ in the image. Try using 200 or 400, at least to start, for the greatest dynamic range and lowest image noise. The beauty of lunar imaging is that even a small 60-mm refractor or 10-cm reflector can produce stunning images. Aperture isn’t a major factor, as the camera is using the telescope as a giant telephoto It’s easy to take high-quality images of the lunar disk. RICHARD JAKIEL he digital imaging revolution has taken astronomy by storm. Spectacular images recorded by amateurs using digital single- Tlensreflex(DSLR)cameras,specialisedplanetarycameras and large-format CCDs dominate the pages of this magazine. But theimagingdevicesyoumost likely own are smartphones, tablets 11 and compact ‘point-and-shoot’ cameras. Surprisingly, these simple Equipped with only a 4-mm reflector and modest Canon PowerShot A530 camera, 13-year-old Harrison devicesarecapableofproducingpretty,evenstunningimagesof McGaha snapped this excellent view of a gibbous Moon. ESO/G. BRAMMER ESO/G. HARRISON MCGAHA HARRISON 38 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 () SEAN WALKER S&T: RICHARD JAKIEL () JAKIEL RICHARD lens. This optical arrangement — telescope, eyepiece This makes centring the Moon easier and reduces Left: By purchas- and a camera with an attached lens — is called afocal vignetting (reduced image brightness) around the ing an adjustable photography. frame’s periphery. adapter, you can attach a smart- While unguided telescopes can produce nice If possible,trynottousetheautomatic-exposure phone or small results, a telescope that’s tracking the Moon will mode, as thistendstounder-oroverexposethe digital camera generally produce better, less blurry images. If you image. (That said,it’seasiertobringoutdetailin directly to a tele- have a steady hand, then just centre the camera’s lens an underexposed image via computer processing.) scope’s eyepiece. over the eyepiece and use the self-timer function to A technique called bracketing works particularly Right: Compare the detail and secure decent images. well with lunarimaging.Byshootingmanyimages contrast in these However, to get the sharpest images and best over a wide rangeofexposuresandISOs,youcan lunar images resolution, some mechanical help will come in accommodate the huge brightness range of lunar taken with a handy. Almost indispensable for basic astro-imaging features and work around any blurring induced by smartphone (left) is a good photo tripod. Most cameras have a ¼-20 atmospheric turbulence. and a point-and- shoot digital threaded hole for attaching it, or you can purchase an While capturing images, use the smartphone’s camera (right). inexpensive tripod adapter for your smartphone. (In display or thecamera’s‘live-screenview’tocheck fact, most ‘selfie sticks’ employ a simple yet effective your framing and focus. You can experiment with tripod adapter.) If tripods aren’t your style, then get a the camera’s optical zoom, if it has one, to capture the smartphone or compact-camera adapter that clamps smallest surface details, though changing to a higher- onto the focusing tube and positions the camera lens power eyepiece can work just as well. But don’t use directly over the eyepiece. the digital zoom — smartphone users, take note! — Technology offers alternatives to using the self- because that doesn’t actually record finer details. timer approach. Perhaps your camera can be used Finally, shooting lots of images is a good hedge with a mechanical or electronic remote release. With against ‘things that go bump in the night’. Almost some cameras a wireless Bluetooth controller can ‘trip’ anything that can go wrong often will — ranging the shutter from up to 30 feet away. from knocking the telescope off target to losing focus, vignetting, weird internal reflections, power loss and Let’s go imaging unexpected weather changes. It’s time to put your equipment and technique to Even a basic camera is capable of shooting the practice by doing some lunar imaging. Before you Moon in a wide variety of situations. For example, head outside, however, make sure the camera lens you can capture faint Earthshine on the darkened is clean and that the largest possible image file is lunar disk when the Moon is near new. Or record its selected. Make sure your battery is charged — and sequence of phases over an entire lunar cycle. Not only turn off the flash! will you learn how the surface brightness changes Point your telescope at the Moon, focus the with phase, but you’ll also have an impressive photo eyepiece, and then position the camera lens directly mosaic once the project is completed. The bottom line: over the eyepiece. Make sure it’s pointing straight don’t be afraid to experiment, have fun, and go shoot in, not tilted, to minimise distortion. Now use the lots of images! ✦ telescope’s focuser to produce a crisp image onto the camera’s display. Go with low-power eyepieces, which Frequent contributor Richard Jakiel observes everything tend to have larger field lenses and good eye relief. from the nearby Moon to distant galaxies. www.skyandtelescope.com.au 39 New Product Showcase ◀ ELECTRONIC ALIGNMENT iOptron has announced the PoleMaster, an electronic polar finderscopethathelpsyouquicklyandeasilyachievenear-perfectpolaralignment.ThePoleMaster is a small optic with an integrated camera that attaches in front of the polar finderscope on most iOptron equatorial mounts. Once installed, the unit functions in conjunction with the included PoleMaster PC software, which quickly plots your polar star field and marks where the true polar axis is,enablingyoutoadjustyouralignmentuntilyouarewithin30arcminutes.Itsopticalalignment can be calibrated to match the true rotational axis of your mount. The device works for both Southern and Northern Hemispheres. PoleMaster connectstoWindowsPCsviaamini-USB cable.Besuretoselecttheproperadapterforyourmountwhenordering. ▾ OBSERVING AID Universe2go has unveiled apersonalplanetariumdevicethatcombinesyour Apple or Android smartphone with an innovative viewer that projects constellation lines, star names andotherusefuldataoveryourrealviewofthe sky.Thisinteractiveviewerworksinconjunction with the Universe2go planetarium app by simply inserting your device into the viewer, which then projects your smartphone screen over your field to match the star patterns, to produce an ‘augmented reality’ experience. The app plots roughly 120,000 stars, as well as the complete Messier and NGC catalogues, and includes over 3 hours of descriptive information. See the manufacturer’s website for additional details. ▴ GO TO MAK Orion Telescopes & Binoculars has introduced the StarSeeker IV 150mm GoToMak-CassTelescope.Thiscompact15-cmf/12Maksutov-Cassegrain telescope has enough aperture to provide satisfying views of the Moon andplanets,aswellasmanydeepskyobjects.Thetelescoperidesupona single-arm, alt-azimuth Go To mount with dual optical encoders, enabling users to slew to objects or move the telescope by hand without losing the GoToalignment.TheStarSeekerIVhandcontrollerfeaturesanextensive database of more than 42,000 celestial objects, including stars, double stars,galaxies,nebulae,starclustersandmore.Thetelescopeincludesa 2-inchvisualbackwitha2-to-1¼-inchadapter,a90ºstardiagonal,23-and 10-mm wide-field 1¼-inch eyepieces, and an Orion EZ Finder II reflex sight. New Product Showcase is a reader service featuring innovative equipment and software of interest to amateur astronomers. The descriptions are based largely on information supplied by the manufactur- ers or distributors. Australian Sky & Telescope assumes no responsibility for the accuracy of vendors’ statements. For further information contact the manufacturer or distributor. 40 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 Cosmic Relief on the ground has become deeper and livelier. Commander Chris Hadfield made Earth’s first astronaut music video: David Bowie’s ‘Space Oddity,’ actually performed while floating in a tin can far above the world. It was an inspired choice. Bowie, who was 10 years old when Sputnik was launched, poetically explored space travel as a metaphor for risk and transcendence. Art helps us connect with and process the universe that science reveals. And now, by showing their artistic sides, astronauts are sharing more broadly the inspiring, transformational potential of the space experience. NASA Scott Kelly has used social media artfully to communicate both daily details and moments One year in orbit of insight. With his #EarthArt series he has shared stunning ISS astronauts are reviving our passion for space travel in novel ways. images of our planetary home presented with casual but sharp stronaut Scott Kelly and its gravity, and today we humans descriptions, curating in real time Cosmonaut Mikhail are perfectly attuned to its surface an awe-inspiring art project for AKornienko have now returned environment, in ways that become the growing number of Earth’s triumphant from their ‘Year in obvious when we leave it. inhabitants who have an internet Space’. Since March 2015, these men Space changes us physically, connection. He often wished us had orbited our planet aboard the with the lack of gravity especially good morning or good night from International Space Station (ISS). taking its toll. Space also affects space with a stirring view of a It’s easy to take the ISS for people psychologically and crescent Earth, an iridescent thin granted, and I’ll admit at times I’ve spiritually. Those who have band of blue shining against the grumbled about its share of the seen Earth from above report a great darkness. NASA budget compared with that sense of profound communion Yes, we humans are well of my own pet planetary probes. with all of humanity and with adapted to Earth’s land surfaces But the Year in Space has rekindled the biosphere, and a feeling that but deeper in our history was a the idealistic and romantic our global conflicts would ease time when life was confined to excitement, fuelled by the Apollo if more people could gain that the oceans. The move to the harsh missions and science fiction, which perspective. Unfortunately, only a environs of the land was difficult as a kid had me imagining we small number of individuals have but ultimately worth it. Perhaps would soon be widely inhabiting been in orbit and experienced this the halting beginning of our the Solar System. ‘overview effect’. extraterrestrial stage is a moment of DAVID GRINSPOON Kelly and Kornienko used Yet something has changed in similar evolutionary potential. Our is an themselves as experimental subjects, the way we are now experiencing planet as it really is — indivisible, astrobiologist, author, and gathering valuable data on human space. The Year in Space is part beautiful, and precious — is senior scientist responses and adaptations to long- of a delightful trend of astronauts revealed to us through the space at the Planetary Science duration spaceflight that will be key taking advantage of social media perspective. The more people who Institute. Follow him on for missions to Mars or elsewhere. and other tools to share their see it, the better equipped we’ll be Twitterat@ DrFunkySpoon. Life has evolved for 4 billion years experiences in new and more direct to meet the global challenges of the in close concert with the Earth and ways. The connection with people coming century. ✦ www.skyandtelescope.com.au 41 Binocular Highlight MONOCEROS M50 USING THE n g WHEN N 5° E bino Late April 11pm cu la r Early May 10pm v i e CANIS Late May 9pm M47 w MAJOR Early June 8pm M46 Late June 7pm LES These are standard times. HOW α Go outside within an hour or so α of a time listed above. Hold the PUPPIS map out in front of you and turn it around so the label for the direc- β tion you’re facing (such as west (CAUDA) SERPENS or northeast) is right-side up. The M46 and M47 in Puppis curved edge represents the hori- zon, and the stars above it on the F η a f there’s one big category of deep sky object that binoculars are best at map now match the stars in front c i n g showing, it’s undoubtedly open clusters. While most globular clusters of you in the sky. The centre of the ν and galaxies more or less look alike through binos (with a few notable map is the zenith, the point in the E SCUTUM a s I M17 M11 t exceptions), just about every open cluster has its own character. They skydirectlyoverhead. 19 run the gamut from big, bright and splashy, to small, dim and hazy. You h can sample some of this range by aiming your binoculars at the Puppis Turn the FOR EXAMPLE: M25 Messier pair, M46 and M47. mapsothelabel“FacingSW”is An easy way to find M46 and 47 is to start from Canis Major. Draw right-side up. About a third of the M22 a line from Beta (β) Canis Majoris (or ‘Mirzam’) through Sirius, and way from there to the map’s centre σ continue on for twice the distance between the two stars. That brings is the brilliant star Canopus. Go π SAGITTA you to the cluster duo. Both objects comfortably fit in the same field of out and look southwest nearly a τ ordinary binoculars. third of the way from horizontal to M46 and 47 are one of my favourite binocular pairings because each straight up. There’s Canopus! cluster is so distinct. The more obvious of the two is M47. Its brightest stars trace a conspicuous equilateral triangle with a clutch of fainter stars NOTE: The map is plotted for 35° scattered about. It’s a pretty sight, but somehow, the longer you look, the south latitude (for example, Sydney, less impressive it seems. With M47, what you see is what you get. Buenos Aires, Cape Town). If you’re By contrast, M46’s beauty is subtle to the point of almost being elusive. far north of there, stars in the north- It’s a rich cluster, but its stars are much fainter than those in M47 — ern part of the sky will be higher and most are magnitude 10 or dimmer. As a result, even under good skies, my stars in the south lower. Far south of F a 10×30 image-stabilised binoculars show M46 as just a small, uniformly 35° the reverse is true. c in lit haze. I have to use my 15×45s to begin to tease out individual stars. And under light-polluted conditions, the cluster disappears altogether, even while neighbouring M47 remains visible. ✦ ONLINE –1 You can get a sky chart 0 customised for your 1 location at any time at GARY SERONIK 2 Gary Seronik is an experienced observer and telescope maker, who also SkyandTelescope.com/skychart authors the Telescope Workshop column in this magazine. You can contact 3 Star him via his website, garyseronik.com. 4 magnitudes 42 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 N g o n i r c t h a F 13 h M51 VENATICI CANES MAJOR β URSA +40 ° γ F a 10 W BOÖTES α h c N i 16 n h g g ν n δ i c BERENICES a ζ F COMA MINOR LE0 BOREALIS α M3 CORONA HERCULE ε ζ Arcturus Sickle δ ε +20 η ° β α γ CANCER τ β LEO (CAPUT) M44 SERPENS θ ε α Regulus δ VIRGO M5 C α T I 0 ° L I P M67 γ C κ E ζ OPHIUCHUS ζ ε M12 β α δ Spica ε E CORVUS CANIS MINOR δ Q M10 SEXTANS U LIBRA A γ CRATER α T Procyon ν α –20 O ° R α ζ γ ε β HYDRA β π t Alphard s η M48 δ σ e W π σ ι g M4 θ Zenith α ξ n ANTLIA i M23 Antares –40° ν c τ a M19 δ κ M46 F M20 SCORPIUS γ τ h ω Cen 7 γ MONOCEROS M21 M62 β η ρ ε α LUPUSε CENTAURUS δ M47 µ M6 µ κ M93 M8 NORMA µ ξ λ υ CRUX γ λ ζ γ ζ Rigil PYXIS β λ M22 ° M7 –60 Kent δ α η Car κ VELA η Sirius δ Hadar β α λ φ CIRCINUS δ θ α ζ η ε η ζ κ M41 α β α δ γ σ τ TELESCOPIUM ARA TRI NGULUM θ ι γ PUPPIS ε ζ CORONA AUSTRALIS 6397 AUSTRALE π TARIUS α MUSCA ε β CANIS MAJOR α APUS ° –80 2516 CHAMAELEON VOLANS CARINA ν α PAVO OCTANS Canopus PICTOR α 30 Dor β COLUMBA α β β Large –80° γ α Magellanic β Cloud DORADO W INDUS S n g HYDRUS g α in SE 47 Tuc α c RETICULUM Fa Small Galaxy Magellanic 22 α h Cloud 4 Double star h TUCANA 1h Variable star α Open cluster HOROLOGIUM Diffuse nebula –60° Achernar Globular cluster Facing South Planetary nebula www.skyandtelescope.com.au 43 Tonight’s Sky A secret stellar flame The challenge of finding special stars hidden among the thousands. And you would cause the sun to see your light one night in a thousand years, how would men believe And then be shamed and adore…” You cover darkness with a thousand secret flames But now the intermittent blankets of day, clouds With your love, oh my love, oh my love, my love… and bright moonlight are superseded in much of — Michael Dunford and Betty Thatcher, our world by the permanent cover of light pollution. The Young Prince and Princess It’s up to us who care about the stars and the sky to keep fighting to educate the public about the many n February’s column, I discussed the desirability of and serious negative impacts of light pollution. If observing a thousand stars and how to go out and you aren’t familiar with the International Dark Sky Ifind them. This month, I look at the two sides — Association, check out the organisation and its work practical and mystical — of such observations. The on light pollution at darksky.org. mystical calls for us to see the stars as “a thousand Although it may sound outrageous, I suggest that secret flames”. you try to observe a thousand individual stars or star To imagine the stars as fire is a potent idea, even if systems, regardless of whether anyone has placed the truth of it is that they’re nuclear fires, producing them on a list of visually pleasing double stars, or energy by fusion rather than combustion. In the 19th variable stars, or very red stars. Of course, the best century, scientists calculated that even an object as place to start in sampling a thousand suns is with massive as the Sun could only burn for a few thousand stars that are bright enough to see with the naked eye years by ordinary chemical reactions. The true nature and therefore appear prominent, perhaps colourful, of stellar fire was indeed a tremendous secret until the through the telescope. Record your observations 20th century, when Einstein unlocked it. of each star. Ideally, you should also learn facts FRED SCHAAF Fred schaaf has Cloaks, both natural and artificial, keep the flames about each of the stars, to determine how each is an hadalifelong of the stars a secret. The scattering of blue by our individual. And fortunately someone has done much love affair with thesky.He atmosphere by day conceals the stars. The big reveal of this fact collecting for you — retired professional welcomes your comments at at twilight is astonishing — as demonstrated by Isaac astronomer Jim Kaler. fschaaf@aol. com. Asimov’s story ‘Nightfall’. That story illustrates Ralph Kaler’s website (http://is.gd/kalerstars) features Waldo Emerson’s quote, “If the stars should appear portraits of individual stars. He regularly adds to the site and as of December 2015, the number of stars profiled had reached 892. Coincidentally, the catalogue of the ancient Greek inventor of the magnitude system, Hipparchus, includes about 850 stars. These numbers approach 1,000, so you can see that it’s possible to observe and study that many. If, however, observing 1,000 individual stars sounds too challenging to you, what should you do? Start with 100. You may find achieving the first 100 easier than you thought. And after that’s accomplished, you’re on your way to a thousand. A star can be a ‘secret flame’ if its characteristics are unknown to you. You can learn the secrets of many a star before observing by consulting Kaler’s site or other sources on your bookshelf or the internet. But be sure you don’t let that knowledge remain unvisualised. If you do, it could easily wither away into dryness or be forgotten. But you won’t forget the hidden realities of the stars once you’ve actually seen the individual stars ESO/Y. BELETSKY themselves, burning in the sky. ✦ 44 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 ▴ The thin crescent Moon sets behind Hanga Kio’e, a restored Moai on the outskirts of the town Hanga Roa on Easter Island. Photo by Kevin Fox. www.skyandtelescope.com.au 45 Celestial Calendar Mars and Saturn at opposition Now’s the best time of the year to see the ‘Red’ and ‘ringed’ planets. JONATHAN NALLY t’sthebattleoftheplanets LUPUS May 20–24, May 20 LIBRA duringMayandJune,astwo 8pmlocaltime Iof them reach opposition and therefore present their best viewing Mars opportunitiesoftheyear. May 21 But let’s start with Mercury, Antares which begins May lost in the ARA eveningtwilightasitheadsforits May 22 SCORPIUS transit(seepage28).Itwillsoon Saturn reappear in our morning skies and putonagoodshowforafewweeks May 23 fromlateMaytomid-Juneinthe OPHIUCHUS northeast prior to dawn. Normally the superstar of the SERPENS CAUDA SAGITTARIUS twilight (whether morning or May 24 evening), Venus is lost to us at the moment, as it is on the Looking East other side of the Sun (superior Saturn, Mars, the Moon and the star Antares will make an attractive grouping in late May. conjunction) and therefore not visible. But it will return to our evening skies in July. CETUS Dawn, June 2 June 1 NowwecometoMars,which 1 hour before sunrise reachesoppositiononMay22. Opposition is where a planet and PISCES the Sun are 180 degrees apart on PEGASUS thesky,whichmeansthatasthe June 2 Sunsetsinthewest,theplanet risesintheeast—makingit visible all night long. Opposition is not the same as closest approach, ARIES June 3 although they’re usually very closetogether.Inthecaseof ANDROMEDA Mars this year, closest approach TRIANGULUM Mercury toEarthwilloccuronMay31ata distance of 75,279,145 kilometres. Closest approach is when a planet Looking Northeast appears at its biggest. Mars will Mercury will be visible on the northeastern horizon in the hours before dawn from late reachanapparentdiameterof18.6 May to mid-June. arcseconds at the end of May. Jupiter is high in the northern motionwillendonMay10,and see its fabulous rings and several sky at the moment, shining brightly Jupiter will once again seem to be of its moons. Look for the grouping at around magnitude –2. The planet headingintherightdirection. of Saturn, Mars, the Moon and has been undergoing retrograde Saturn comestooppositionon Antares in late May (see diagram). motion for a while, which is where June 3. The ringed planet will be Finally, we’ll reach the southern it ‘seems’ to be going backwards in well placed for viewing during late winter solstice on June 21, which is itsorbit.Inreality,it’ssimplythat May through to the end of June. when the Sun is furthest north in Earth has been ‘overtaking’ it on Ifyouhaveaccesstoatelescope, our skies and the hours of daylight theinsideorbitallane.Retrograde now’s the time to take a peek and are at their shortest. 46 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 Events Of Note May 8 Aldebaran 0.5° south of the Moon MAY 2016 10 Jupiter stationary S 14 Regulus 2° north of the Moon Phases 15 Jupiter 2° north of the Moon New Moon May 6, 19:30 UT 19 Spica 5° south of the Moon First Quarter May 13, 17:02 UT Full Moon May 21, 21:14 UT 20 Mars 1° north of Delta Scorpii Last Quarter May 29, 12:12 UT 22 Mars 6° south of the Moon 22 Mars at opposition Distances 22 Antares 10° south of the Moon Perigee May 6, 04h UT 23 Saturn 3° south of the Moon 357,827 km Apogee May 18, 22h UT Jun 3 Saturn at opposition 405,933 km 5 Mercury greatest elongation west E W 8 Mercury greatest latitude south 11 Regulus 2° north of the Moon JUNE 2016 12 Jupiter 1.5° north of the Moon Phases 15 Spica 5° south of the Moon New Moon June 5, 03:00 UT 17 Mars 7° south of the Moon First Quarter June 12, 08:10 UT 19 Mercury 3.9° north of The Hyades Full Moon June 20, 11:02 UT 19 Antares 10° south of the Moon Last Quarter June 27, 18:19 UT KL RÜ 19 Saturn 3° south of the Moon NÍN ANTO Distances 20 Mercury 4° north of Aldebaran N Perigee June 3, 11h UT 21 Winter solstice 361,140 km 30 Mars stationary Apogee June 15, 12h UT Times are listed in Australian Eastern Standard Time 405,024 km Meteors anytime, anywhere CON STOITSIS In addition to meteor showers, make sure you keep your eyes peeled for sporadics. iewing meteor showers viewing. With the Moon, if it’s is free, it’s fun, and it’s a within the first few days of a Full V reminder that there is a phase (ie. full or gibbous), you’ll vast universe out there. A shower probably find that the sky is too occurs when Earth passes near bright to see a shower, or at least a comet’s orbit and the debris the fainter meteors. The best time particles left in the comet’s wake for viewing is when the Moon is hit Earth’s atmosphere. between New and First Quarter, as The dates of showers are this is when it casts no or very little predictable, so all you have to do is light and sets before midnight. hope for the right conditions and As well as meteor showers there wear the appropriate gear to keep are also ‘sporadic’ meteors — lone warm. It’s also important to select streaks of light that can appear a suitable viewing spot. Preferably, anywhere in the sky, anytime, there should be an unobstructed although they’re most often seen in view of the sky, so beware of trees, the few hours before dawn. June is buildings, houses and anything else the peak month for sporadic activity that might block your view. Most of in the Southern Hemisphere, so if all your chosen viewing spot should you’re outside in the early hours, be as dark as possible, away from remember to look up! sources of artificial light. Don’t forget to check the Con Stoitsis is the director of the Sporadic meteors can appear in any part Astronomical Society of Victoria’s comet weather forecast and Moon of the sky at any time. ESO/G. Brammer conditions, as both will affect your and meteor sections. www.skyandtelescope.com.au 47 Celestial Calendar More of the Centaur’s gems Ten easy double stars for small- to medium-sized telescopes. ROSS GOULD here are many hundreds you might visit the binary SLR 18, bound binary. A degree north from of double stars suitable slightly southwest of Omega. SLR 3 Cen is another William Herschel Tforsmallandmedium 18 is one of a small list of doubles discovery, 4 Centauri, a fairly wide telescopes, from 60-mm refractors discovered in the 1890s by Richard unequal pair, also attractive for to 20-cm reflectors. For this issue SellorsatSydneyObservatoryusing small telescopes. South-east from I’veselectedtenofthem,allfrom its29-cmrefractor.Thestars,pale 4 Cen some 25′ is the easy little thesamepartofCentaurus. yellow and 7th magnitude, are a pair HWE 74, with 7th- and 10th- Using Gamma Centauri as very close pair, although wider now magnitude stars nearly 6″ apart. our first guide star, some 3° east- than when discovered. The most Several doubles in this area are northeast is I83,oneofseveral recentmeasureis0.72″ in 2010, discoveries by H.A. Howe (HWE), hundred doubles Robert Innes andI’veseenthepairastwodisks of the Cincinatti Observatory, discoveredinthelate1890satthe overlapping at 400× with my 14-cm using its 11-inch refractor. In the CapeObservatory.I83isabinary, refractor. With 18 cm some years 1870s, having noted a lack of the orbit currently reckoned as 173 ago(andSLR18nowider)itshowed observation of southern doubles, years. The fairly bright yellowish as barely separated at high power. Howe and co-workers measured starsarenow0.85 apart,somewhat Our remaining pairs this and sometimes discovered doubles wider than at the time of discovery monthare10degreesorsonorth in the declination zone from 15 to and now nearly at maximum and eastwards from Omega Cen. 35 degrees south. Perhaps Howe’s separation. I’d suggest at least 15 cm TheneatlittlepairHJ 4608,7th most interesting find is y Centauri at 200× or more to split them. magnitude stars 4″ apart, are a (HWE 28), not to be confused with OnedegreesoutheastofI83 yellow pair located one degree Gamma Cen. The 6th-magnitude is the neat unequal pair CPO 13, southwest from 1 Centauri (mag. yellowish stars are a little wider than of 7th and 9th magnitudes, seen 4.2).Thestars1,2,3and4Centauri in 1876, measured at 1.0″ in 2014. An with the 18-cm refractor at 100× are in this region, and our next orbit of period 373 years has recently as a fairly bright orange star with double,eastof1Cen,is3 Centauri been calculated. The separation is a little companion close; a delicate (H 3 101), a William Herschel now approaching maximum. I first and attractive effect. Nearly 10′ discovery, the bright stars making observed y Cen in the 1970s from northwest in the field is HJ 4562, a “beautiful unequal white pair” Sydney using a 15-cm Newtonian, a fairly wide 9th-magnitude pair as Ernst Hartung noted. It’s a fine which provided a bare separation at providing a nice contrast. object for small telescopes as well high power. More recently, with an Nearby is Omega Centauri. as larger ones, though probably an 18-cm refractor at 180× it was a barely After taking in its amazing view, opticaldouble,notagravitationally split pair. It’s an attractive object for medium apertures. Precious doubles in Centaurus Finally, 1 degree west of y Cen is HWE 74, a fairly wide and unequal Position Date of Star Name R. A. Dec. Magnitudes Separation Angle Measure Spectrum pair. Hartung (in whose book it I83 12h 56.7m -47° 41´ 7.4, 7.7 0.85” 236 2014 F5IV/V is wrongly numbered HWE 24), CPO 13 13h 00.3m -48° 36´ 7.2, 9.2 5.1” 068 2004 G8IV notes the unusual colours of the HJ 4562 12h 59.5m -48° 32´ 8.9, 8.9 11.3” 077 2010 F4V+F4V pair, deep yellow and reddish, clear SLR 18 13h 22.9m -47° 57´ 6.7, 7.2 0.7” 243 2010 A4V with 10.5 cm. The proper motions h m ´ HJ 4608 13 42.3 -33° 59 7.4, 7.5 4.1” 010 2013 F5 of the stars are large and the same, h m ´ HWE 94 13 48.9 -35° 42 6.6, 10.2 11.3” 359 2013 F8V+K6V suggesting it’s a binary. Parallax h m ´ 3 Cen (H 3 101) 13 51.8 -33° 00 4.5, 6.0 7.9” 104 2013 B5III+B8V measures give the distance to HWE 4 Cen (H N 51) 13h 53.2m -31° 56´ 4.7, 8.5 14.8” 185 2013 B4V 74 as 96 light-years from Earth. y Cen (HWE 28) 13h 53.5m -35° 40´ 6.3, 6.4 1.0” 315 2014 F4V HWE 74 13h 55.3m -32° 06´ 7.2, 9.8 5.8” 117 2013 G5 Ross Gould can be reached at Data from the Washington Double Star Catalog [email protected] 48 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 Two views of C/2013 X1 (PANNSTARS), taken three days apart: on January 9 (left) and 12 (right). The comet should make a fine sight through binoculars during May and June, and might just reach naked-eye brightness under the darkest of skies. Images courtesy of Gerald Rhemann and Wolfgang Moschner. the sudden brightening was an outburst whereas others were not Bright prospects as sure, suspecting that it may have been more in the nature of a surge lifting the intrinsic brightness to for comet viewing a new level likely to be maintained throughout the apparition. Keep an eye on comet C/2013 X1 as it climbs high From the data to hand at the time of writing, it appears that both into the sky during May and June. DAVID SEARGENT may have been correct. There is evidence of at least a small outburst, ay and June will witness mid-month before briefly clipping but the comet also appears to have the peak performance Sagittarius as its apparent speed increased its general activity and, Mof comet C/2013 X1 revs up on the way to its passage once again, made another jump in (PANSTARRS) as it climbs high past Earth. Following its nearest intrinsic brightness. into the early morning sky following approach, the comet will cross Brightness estimates made its April 20 perihelion passage of Telescopium and arrive in Ara at the start of this year ranged 1.31 astronomical units from the during the last three days of June. from about 8.5 to near magnitude Sun. It will be approaching Earth As I have noted in previous 7. Assuming that the intrinsic for most of the period covered here, issues, this comet turned out to brightness stabilises around the until June 21 when it passes by us at be significantly brighter than fainter end of this range, the comet a little less than 0.64 a.u. had been anticipated during is likely to be around magnitude Southern Hemisphere observers the closing weeks of 2015. This 7–7.5 in early May, peaking at will have the box seat for this trend continued into 2016 with approximately magnitude 6 when performance. As May begins, the a surprising jump in brightness closest to Earth and in the 6–6.5 comet will be visible before dawn estimates occurring shortly after range by the end of June. There is a almost directly east in Aquarius, New Year. With the comet then possibility that the comet might be where it will spend the month, receding from Earth and, at the seen with the naked eye from very climbing higher into the sky and same time, sinking fast into the favourable sites, although any such moving near the line of sight as evening twilight, magnitude sightings — if they occur at all — it approaches our planet. During estimates had quite a deal of will most probably be marginal. June’s first week it will be high scatter, which did not help in the in the sky, crossing into Piscis interpretation of what was actually David Seargent’s book on comets, Austrinus and then entering the happening to the comet. Some Snowballs in the Furnace, is available faint constellation Microscopium observers were convinced that from Amazon.com www.skyandtelescope.com.au 49 Celestial Calendar Going all hyper JUPITER IN MAY Telescope users should plan to This easy-to-find super-sized star puts our Sun to shame. catch Jupiter right around the end of twilight, while it’s still high on the meridian or just past it. Below are V766 Cen is located ur variable star target this V766 Cen is a truly huge star, the times, in Universal Time, when at 13h 47m 10.86s, issue is V766 Centauri, an with a diameter of six astronomical Jupiter’s Great Red Spot should rotate –62° 35” 23.0” unstable yellow hypergiant units(onea.u.istheaverage across the planet’s central meridian. (epoch J2000). O The dates, also in UT, are in bold. This chart, which and one of only about ten known in distance from the Earth to the is approximately the Milky Way. For the information Sun).Ithasasmallercompanion April 15, 5:28, 15:23; 16, 1:19, 11:15, 4 degrees wide, thatfollowsweneedtogivethanks star orbiting at a separation of 21:10; 17, 7:06, 17:02; 18, 2:57, 12:53, comes courtesy of to Sebastian Otero, a binocular and 9.6a.u.Thatnumberisabit 22:49; 19, 8:44, 18:40; 20, 4:36, 14:31; the AAVSO. North is up, and visual naked-eye variable star specialist misleading, as orbital separation 21, 0:27, 10:23, 20:18; 22, 6:14, 16:10; magnitudes are who observes from light-polluted refers to the centres of mass of the 23, 2:05, 12:01, 21:57; 24, 7:52, 17:48; shown with decimal Buenos Aires, and who co-authored stars — but this pair is essentially 25, 3:44, 13:39, 23:35; 26, 9:31, 19:27; 27, 5:22, 15:18; 28, 1:14, 11:09, 21:05; points omitted to a paper on V766 Cen in the in physical contact, and definitely avoid confusion 29, 7:01, 16:56; 30, 2:52, 12:48, 22:44. journal Astronomy and Astrophysics interacting, within an extended with faint stars — so 75 denotes a (Chesneau and Meilland et al. 2014 nebula. Their mutual orbit has a May 1, 8:39, 18:35; 2, 4:31, 14:26; 3, 7.5-magnitude star. A&A 563, A71). period of 3.5 years. 0:22, 10:18, 20:14; 4, 6:09, 16:05; 5, V766 Cen is located about 11,700 2:01, 11:56, 21:52; 6, 7:48, 17:44; 7, 3:39, light-years from Earth, straight 13:35, 23:31; 8, 9:26, 19:22; 9, 5:18, 15:14; 10, 1:09, 11:05, 21:01; 11, 6:57, down the dusty plane of the 16:52; 12, 2:48, 12:44, 22:39; 13, 8:35, Galaxy. Despite that vast distance, 18:31; 14, 4:27, 14:22; 15, 0:18, 10:14, it shines at a stunning 6th to 7th 20:10; 16, 6:05, 16:01; 17, 1:57, 11:53, magnitude. This star is extreme. 21:48; 18, 7:44, 17:40; 19, 3:36, 13:31, V766 Cen ranges irregularly 23:27; 20, 9:23, 19:19; 21, 5:14, 15:10; 22, 1:06, 11:02, 20:57; 23, 6:53, 16:49; frommagnitude6.1to7.5,witha 24, 2:45, 12:40, 22:36; 25, 8:32, 18:28; small 0.2-magnitude eclipse period 26, 4:23, 14:19; 27, 0:15, 10:11, 20:07; superimposed. The finder chart 28, 6:02, 15:58; 29, 1:54, 11:50, 21:45; provided will help you locate it on 30, 7:41, 17:37; 31, 3:33, 13:29, 23:24. thesky,notfarfromacoupleof attractive open star clusters: NGC These times assume that the spot will be centred at System II longitude 5821 immediately to the south, and 234°. It will transit 1.6 minutes earlier NGC 5316 to the northeast. for each degree less than 234°, and 1.6 minutes later for each degree Alan Plummer observes from the greater than 234°. Features on Jupiter Blue Mountains west of Sydney, and appear closer to the planet’s central meridian than to the limb for 50 can be contacted at alan.plummer@ minutes before and after they transit. variablestarssouth.org Targets Leo’s starry sickle Bright stars and strange galaxies hide in this constellation’s regal mane. Where Leo waits King Sol in dog-days’ reign toward the west, and diamond-like Regulus marks And Regulus shines diamond-like and bright, the end of its handle. We have a brilliant visual aid When springtime wakes and summer smiles again for finding the Sickle this year: Jupiter, the king of Tillharvestmoonbeamsyellowinthenight; planets, quite suitably shares Leo’s lordly realm, sitting Six suns, with four stars sparkling in its train, southeast of the Sickle. Although just a visitor to the Like question-mark which faces to the right. kingdom, Jupiter well outshines Leo’s royal stars. Or secret symbol written clear and plain, The tip of the Sickle’s blade is marked by Epsilon Astarrysickleglittersinmen’ssight. (ε) Leonis, and to its west-southwest we find the star — Charles Nevers Holmes, TheStarrySickle, 1916 Lambda (λ).Throughmy130-mmrefractoranda wide-angle eyepiece at 37×,yellow-orangeLambda ur king of beasts, Leo, the Lion, reigns shares the field of view with the spiral galaxy NGC supreme in the northern part of our skies at 2903,whichdangles1.5° south of the star. The galaxy Othe moment, watching over his domain from appears oval, twice as long as it is wide, and tipped a just north of the celestial equator. The constellation’s biteastofnorth.Itbrightenstowardatinycore.Faint most distinctive part is an asterism known as the stars flank the galaxy’s southern tip, the brighter SickleofLeo.TheSickle’shighlycurvedbladeisopen onetotheeast.At91× an ashen halo reaches a size of roughly 9½′×4′. A considerably brighter, mottled inner region covers about 5′×2½′,anditstinycore 10h 20m 10h 00m h 40m seems to be elongated. Boosting the power to 117×, + g the inner region looks quite patchy, and its core is definitely elongated. A faint star lies between the +25° ¡ c 3162 h Hickson 2903 3226 a +20° Algieba 3227 3222 LEO 3239 d +15° 2 s 3 4 5 Regulus i _ × 6 Frosty Leo At 202 , Uwe Glahn’s 37-cm reflector revealed the core, bar and curving stretch of NGC 2903’s spiral arms. Deep Star magnitudes 7 R j 8 sky images show the dramatic core, made vivid with +10° star-forming activity. Moderate apertures will pick out the oval shape and bright core. Larger scopes and more t magnification will draw out the arms and may even show the galaxy’s central bar. UWE GLAHN UWE BILL SNYDER 52 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 ° flanking stars, closer to the brighter one. 10h 25m 10h 20m 10h 15m +23 Through my 25-cm reflector at 115×, NGC 2903 3162 spans 10′. A slightly wavy line of four stars serves as a platform for NGC 2903’s southern end, and a faint star huddles against the western side of the northern end. At 166× the core envelops a tiny, fuzzy nucleus, and 3187 +22° the mottled region has brighter patches at its northern 3193 3190 and southern ends. The northern patch becomes Hickson prominent at 213×, while the southern one is less 3185 pronounced. The core brightens toward the centre, but no discrete nucleus is evident. The brightest star in the Sickle’s curve is +21° Gamma (γ) Leonis, commonly known as Algieba, a delightful double star for any telescope. My 105- mm refractor at 68× reveals a striking pair of golden LEO suns, the 2.4-magnitude primary watching over the 4 3.6-magnitude companion to its southeast. 3226 Algieba’s components form a true binary located 5 6 about 130 light-years away from us. Preliminary 3227 3222 Algieba a 7 orbital elements in the internet-based Sixth Catalog of 8 Orbits of Visual Binary Stars give this pair an orbital Star magnitudes 9 40 period of 554 years, plus or minus 27 years. The 10 apparent separation of the stars is currently 4.7″. If the +1 ° preliminary elements are nearly correct, the separation will sluggishly crawl to a maximum of 4.8″ sometime in the early 2060s and then close to a cozy 0.2″ afew nucleus. NGC 3193 measures about 1¾′ in diameter. centuriesfromnow. NGC 3185 makes an appearance as a low-surface- Climbing 2.0° north-northwest from Algieba brightness oval tipped southeast, and I can barely takes us to Hickson 44, a compact group of four catch a trace of NGC 3187. At 117× NGC 3185 unveils galaxies spanning 18′ on the sky. Through my 130- a slightly brighter centre. NGC 3187 presents a small, mm refractor at 63×, NGC 3190 is easily visible as diaphanous wisp pointed at NGC 3190 that’s seen only an elongated glow tilted west-northwest. NGC 3193 with averted vision. is dimmer and round. It hosts a bright centre, and a My 25-cm reflector at 166× adds a stellar nucleus 9.6-magnitude star nuzzles its northern border. At 91× to NGC 3193, while my 38-cm reflector at 216× greatly NGC 3190 is about 3½′ long and one-quarter as wide. prettifies Hickson 44, making features much easier to It holds a brighter, elongated centre with a starlike discern. The larger scope even teases out part of NGC Along the lion’s mane Angular sizes and Object Type Mag(v) Size/Sep RA Dec. separations are from recent catalogues. ′× ′ h m ° ′ NGC 2903 Spiral galaxy 9.0 12.6 6.0 09 32.2 +21 30 Visually, an object’s size is often smaller ″ h m ° ′ Gamma Leonis Double star 2.4, 3.6 4.7 10 20.0 +19 51 than the catalogued value and varies ′ h m ° ′ Hickson 44 Galaxy group 10.9 – 13.4 18 10 18.0 +21 49 according to the aper- ture and magnification ′× ′ h m ° ′ NGC 3227 Spiral galaxy 10.3 4.1 3.9 10 23.5 +19 52 of the viewing instru- ment. Right ascension ′× ′ h m ° ′ NGC 3226 Elliptical galaxy 11.4 2.8 2.0 10 23.5 +19 54 and declination are for equinox 2000.0. NGC 3222 Lenticular galaxy 12.8 1.3′×1.1′ 10h 22.6m +19° 53′ NGC 3239 Irregular galaxy 11.3 5.0′×3.6′ 10h 25.1m +17° 09′ Frosty Leo Protoplanetary 11 28″ × 14″ 09h 39.9m +11° 59′ www.skyandtelescope.com.au 53 Targets The four ° gravitationally Hickson 2.9 south-southeast of Algieba. My 130-mm refractor ′ bound galaxies displays a 1¼ wedge-shaped glow with a distracting that comprise 10th-magnitude star on its southwestern edge. The compact group star makes an isosceles triangle with 12th-magnitude n44o Hickso ffer stars 2.4′ west and northwest. The galaxy extends a grand study for visual observers. farther westward when seen through my 25-cm × NGC 3185 scope at 166 , with a gauzy, tapering arm reaching presents as an NGC 3193 out toward the western star. There’s a brighter spot almost face-on NGC 3187 on the galaxy’s edge, east of the 10th-magnitude star. spiral, while NGC My 38-cm reflector at 192× brings out a more subtle 3190 is all but edge-on. NGC spot in the galaxy, north of the star, and a stubby barb 3193isaclassic NGC 3190 of filmy light juts south-southwest from the brighter elliptical galaxy. spot. A ghostly glow dwells beyond the galaxy about Thedimmestof two-thirds of the way from the 10th-magnitude star NGC 3185 the group, NGC to a faint star 5.6′ east-southeast. At 216× it becomes 3187,isdetectable through moderate a petite north-south oval, the 15th-magnitude galaxy scopes only CGCG 94-42 (PGC 30585). becauseofits SIEGFRIED KOHLERT Bizarre as my descriptions are, NGC 3239 bright bar; you’ll appears even more peculiar in deep images, looking need aperture or 3190’sdustlane,wornlikeaduskyribbonuponthe something like a lumpy, mirror-reversed π symbol. images to see the glorious tails of its galaxy’s south-southwestern flank. The most likely cause of its tortured appearance is NGC 227 NGC 226 spiral arms. Interacting galaxies 3 and 3 thought to be a galaxy merger. NGC 3239’s weird form reside 50′ east of Algieba, where my 130-mm refractor has lent it the nickname the Loony Galaxy. at 23× merely shows a moderately faint glow. At 63× Whilegalaxiesarethemainfarewhenitcomes it’s evident that two galaxies exist here. Although to deep sky wonders in Leo, let’s finish with a small thehalosblendtogether,eachharboursasmall, dessert — the Frosty Leo nebula, 2.1° north of distinct,brightercentre.NGC3227isovalandtipped Omicron (ο) Leonis. Pointing my 25-cm scope at 166× south-southeast. NGC 3226 balances north of its toward the correct location, I see a slightly crooked, partner,withahalocantednortheast.Uppingthe 15′ line of three bright stars very unevenly spaced magnification to 117×, the pair traverses about 4½′. and dressed in shades of yellow. The nebula sits 12′ NGC3227sportsanovalcorewithaprominent, south-southeast of the brightest star and just outside starlikenucleus,andNGC3226intensifiestowardits the southern corner of a 3′ isosceles triangle of faint centre. NGC 3222 nowjoinsthescene,13′ west of the stars. It’s very small, bluish and roundish with a nearly duo. This little galaxy appears very dim and embraces starlike centre. My 37-cm reflector at 245× shows that a tiny, feeble nucleus. A faint star flickers in and out of Frosty Leo has a bright oval core and a relatively thin, view at NGC 3222’s south-southwestern edge. fainter halo elongated roughly southeast-northwest. I The remarkably strange galaxy NGC 3239 perches estimate a length of 1/3′. Frosty Leo is a protoplanetary nebula. When an aging star roughly the mass of our Sun exhausts its The peculiar and distorted NGC 3239 structure of NGC 3239, hydrogen fuel, it sheds its outer layers while its core also catalogued as contracts. The cocoon of cast-off material reflects light Arp 263, can make for a from the star, and we see a protoplanetary nebula. challenging observation As the collapsing core grows hotter, it eventually — you’ll find neither the warms the nebula enough to emit its own light, and regular glow ball of an elliptical nor the swirling a planetary nebula is born. Frosty Leo’s name springs arms of a spiral. Look from its abundance of dust coated with crystals of instead for a wedge- water-ice. ✦ shaped glow to locate this oddity; studying a deep sky image may help you find the disturbed arms reaching southward. SUE FRENCH SueFrenchwelcomesyourcommentsat [email protected] BOB FRANKE 54 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 Call us andGET quote 0+#!0ĸāĀ+û5+1.ü./0+. $10 !.ē www.opticscentral.com.au AST MAGAZINE OFF! 1300 884 763 From From 95 o 95 $499. DOBSONIAN TELESCOPES$189. ASTRO I OCUL ƫ!(!/0.+*'5) /0!.ĂĆ4āĀĀƵ/0.+*+)5ǫ%*+ 1( ./ Saxon 8" Dobsonian Telescope (8 inch) ƫ!(!/0.+*'5) /0!.ĂĆ4ĈĀƵ/0.+*+)5ǫ%*+ 1( ./ Saxon 10" Collapsible Dobsonian Telescope (10 inch) 4+*ăĀ4ĉĀƵ/0.+*+)5ǫ%*+ 1( ./ '53 0 $!.āąŎ+ġ+ƫ+),10!.%/! + /+*% *!(!/ +,! *#1 . Ƶ(0 ŐĂćăƵ.%,+ ƫ ġăāĀĆā ƵġĂĀĀāĆ ƵġāĆĀĈĆă ƵġĉĀƵă ƵġāĂĀĆ SaxonNEQ6ProMount Free shipping NEW ZWO ASI 1.2mp/colour ( *!0 .5ƫ )!. 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MATHEW WEDEL “Askpeoplewholandhugefishwithlighttackle, emptyspace,buthereandthereyoucan find clumps of them. These groups and whyIdowhatIdo,” clusters are the first steps up a ladder that wrote observer Jay Reynolds Freeman, in small enough to hold in your hands. leads through superclusters, filaments, an essay about hunting deep sky objects In addition to this reward, observing sheets and walls composed of thousands with small telescopes. For amateur galaxies with binoculars shows you or millions of galaxies, to the large-scale astronomers, there are no bigger fish something about the universe. Galaxies structure of the universe. than galaxies, and no lighter tackle than are the building blocks of the cosmos, Which brings us to the Virgo Cluster, binoculars. There’s something particularly and with binoculars you can see them in a collection of up to 2,000 galaxies centred satisfying about catching an object as their native habitat. Mostly that means about 54 million light-years away. As grand as a galaxy with an instrument they’re isolated by vast gulfs of nearly the nearest large galaxy cluster, it has R 4147 4293 4064 24 M85 43944 11 LEO 44450 36 4340 4350 27 4651 S M100 Diamond 95 COMA BERENICES HD 107415 ++15° Denebola 4419 M98 6 ` 4710 Shaft +15° 4298 Arrowhead M91 M88 M99 4459 4212 4866 4571 4477 HD 107288 46894 44733 4168 44435 M90 4461 4267 4216 4639 The Eyes 4438 M84 4654 M866 4388 7 4478 M58M 4371 Vi 9 4647 M59 le V 45 M60 4638 4754 4178 503 4429 ++10° Vindemiatrix 4762 4124 ¡ 4694 4442 X +10° 4417 k 4 Big L VIRGO M49 4698 4535 4526 HD 1088985 4365 / R 4570 On to M 61 Star Magnitudes 12h 00m 12h 20m 12h 40m 3456789 h m 13 00 DINDERMAN GREGG CHART: 56 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 Virgo Cluster: Double V and Shaft 4571 M91 M90 M88 M89 4459 4479 4477 4473 M87 4435 4438 M86 M84 N DEEP SKY FISHING HOLE The Virgo Cluster encompasses some 1,300 to 2,000 galaxies. Sixteen of those galaxies are Messier objects, discovered by Charles Messier and his colleague Pierre Méchain between 1771 and 1781. ROGELIO BERNAL ANDREO www.skyandtelescope.com.au 57 Binocular Observations drawn the interest of both amateur and Virgo Cluster: Diamond and Arrowhead professional astronomers for almost a century. It also draws us in quite literally: our Milky Way Galaxy and the other galaxies of the Local Group are all moving Virgo-wards at 100 to 400 kilometres per second. It’s another in a long line of Copernican reality checks — even our local galaxy club turns out to be a relatively small appendage of something much larger. But it makes for a dramatic demonstration at evening get-togethers: point boldly toward Virgo and announce to everyone present that on a cosmic scale, “we’re headed thataway.” M100 So, we’re going to Virgo — in real life, with our binoculars, and in this article. Nothing has pushed my observing skills 4312 as much as going after galaxies with binoculars. They force me to use every trick in the book (see tip box, page 60). Access to dark skies certainly helps as well. Under clear, desert skies I’ve seen all of the Virgo Messier galaxies through 10×50 binoculars. But even out there, some of them are tough, and I’m not always successful. A 15×70 instrument brings more aperture for catching and concentrating those photons, and more magnification for separating the galaxies from each other and from nearby stars. But whatever binoculars you have handy, give them a try — a few of the big elliptical galaxies should be detectable through M99 almost any clean, serviceable instrument. Of the thousands of galaxies in the 6 Com Virgo Cluster, I’m focusing here on the 16 that are included in the Messier catalogue. Most of them are in the northern reaches of the constellation M98 Virgo, but a handful spill over into neighbouring Coma Berenices. Several search strategies have been published for getting through the Virgo Cluster Messiers (a comparative list is available online at messier.seds.org/more/ virgo_obs.html). Some use the galaxies themselves as landmarks. If you have the right combination of dark skies and N visual acuity to make that work, I say ROGELIO BERNAL ANDREO go for it. I tend to stumble a bit myself ANCHOR STAR Fifth-magnitudestar6ComaeBerenicessitsatthetipofanarrowheadasterism; in this area, so I use the pattern of use it as your home port while locating M98, M99 and M100. foreground stars as a guide. 58 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 An easy starting point is the bright M99 star Denebola at the tail end of the constellation Leo, the Lion. Scanning 7° dueeastwillbringyouto6Comae Berenices, which forms the tip of an arrowhead asterism a little less than 2° across. Three Messier galaxies lie in and around this triangle: M98 is ½° west of 6 Comae, M99 is 1° southeast, and M100 is 2° northeast, just off the northern corner ofthearrowhead.Ofthethree,M100,ata comparatively bright +9.3 magnitude and with no other bright sources nearby to interfere, should be easiest to see. Not only isM100agoodplacetostartatourofthe Virgo galaxies, it’s also a good place to end — after your observing session is over, hit your favourite book, magazine or website to study high-resolution images of this beautifulgrand-designspiralgalaxy. SIGGI KOHLERT M98andM99arebothabouthalf NEXT-DOOR NEIGHBOUR Through binoculars at low magnifications, 6th-magnitude field a magnitude dimmer than M100 and star HD 107170 may interfere with your view of M99. However, 15×70 binos will reveal M99 as a correspondingly harder to see. M99 is the round, condensed patch of haze perched southwest of the star. Gone Fishing Object Galaxy Type Surface BrightnessMag(v) SizeRA Dec. M98 Spiral 13.610.1 9.5′×3.2′ 12h 13.8m +14° 54′ M Spiral 13.2 . 5.4′×4.8′ 12h 18.8m +14° 25′ M100 Spiral 13.4 .3 7.4′×6.3′ 12h 22. m +15° 4 ′ M85 Lenticular 13.0 .1 7.1′×5.2′ 12h 25.4m +18° 11′ M84 Lenticular 13.0 .1 6.5′×5.6′ 12h 25.1m +12° 53′ M86 Lenticular 13.28. 8. ′×5.8′ 12h 26.2m +12° 57′ NGC 4435 Barred spiral 12.510. 2.4′×1.4′ 12h 27.7m +13° 05′ NGC 4438 Spiral 13.610.0 8.5′×3.2′ 12h 27.8m +13° 01′ M88 Spiral 13.0 .6 7.0′×4.0′ 12h 32.0m +14° 25′ M 1 Barred spiral 13.410.2 5.4′×4.4′ 12h 35.4m +14° 30′ M87 Elliptical 13.08.6 7.2′×6.8′ 12h 30.8m +12° 23′ M58 Barred spiral 13.1 .7 5.5′×4.5′ 12h 37.7m +11° 4 ′ M8 Elliptical 12.5 .8 5.1′×4.7′ 12h 35.7m +12° 33′ M 0 Spiral 13.4 .5 .5′×4.5′ 12h 36.8m +13° 10′ M5 Elliptical 12. .6 5.0′×3.5′ 12h 42.0m +11° 3 ′ M60 Elliptical 12. 8.8 7.0′×6.0′ 12h 43.7m +11° 33′ M4 Elliptical 13.28.4 .0′×7.5′ 12h 2 .8m +08° 00′ M61 Barred spiral 13.4 .7 6.0′×5.5′ 12h 21. m +04° 28′ 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. www.skyandtelescope.com.au 59 Binocular Observations M58 theircombinedlightmakesthemalittle easier to spot. Nowgobacktothearrowheadasterism anchored at 6 Comae. This arrow has a crookedshaftthatrunsalmostdueeast, composed of five 8th- and 9th-magnitude stars. The spiral galaxies M88 and M91 lie just southeast of the third and fourth stars in this line, respectively. M88 is one of the closest galaxies to us in the Virgo Cluster, at a ‘mere’ 47 million light-years away.It’salsostronglytiltedtoourlineof sight, which helps concentrate its light. As aresult,it’soneofthebrighterandeasier IJUSTNEEDMYSPACE Binocular observations of M58 can also be hampered by nearby members to pick up with binoculars. field stars. Edging 8th-magnitude HD 109771 just outside your field of view may help; look The same cannot be said for M91. This foranovalcondensationabout8arcminuteseastofthestar. NOAO / AURA / NSF barred spiral galaxy lies almost face-on to us, and at 63 million light-years it’s one brighterofthetwo,butit’slocatedvery is the more easterly, as well as being of the more distant Virgo Messiers. Both near a 6th-magnitude star, HD 107170, and largerandbrighter.Outofallofthe factors make it a challenging catch — at low magnifications it can be difficult to Messier objects, M86 has the highest M91 joins M98 as the Virgo objects that separatethetwo.M98isoffbyitself,like blueshift — it’s actually getting closer to havefoiledmethemostoften.Ifyoudo M100,butit’sfairlydimforaVirgoMessier us as gravity pulls it toward the centre of manage to spot it, consider this: the light galaxy,andIfinditachallengingtarget the Virgo Cluster from the opposite side. that you’re seeing left the galaxy only a under all but the best circumstances. M84 and M86 comprise the western coupleofmillionyearsaftertheasteroid Thenorthernmoststarinthe anchorofafamouslineofbrightgalaxies impact that is thought to have wiped arrowhead,HD107415,isalsothebase called Markarian’s Chain,whichswoops out the dinosaurs. Without that cosmic of a tall, narrow diamond, capped by off to the east and north. Should you accident,we’dprobablystillbelivingin 5th-magnitude 11 Comae Berenices. attempttocatchtheothermembers holesandtryingnottogetsteppedon, Just over 1° east-northeast of 11 Comae of the chain with your binoculars? Of instead of contemplating the universe. is M8, a large lenticular galaxy. M85 is course! The other members are spaced At the end of the arrow we’ve been the northernmost outpost of the Virgo fairly regularly at intervals of 1/3°.Ifyou following, an arc of dim stars curves Cluster, at least for observers using see any of the non-Messier members around to the south. Another gaggle of binocularsorsmalltelescopes. of Markarian’s Chain, the most likely 8th- and 9th-magnitude stars in a nested Nowgobacktothearrowhead will be NGC 443 and NGC 4438.This double-V formationwillhelpyouspot asterismandfollowalinefrom6Comae close couple is known as ‘The Eyes’ for four additional Messier galaxies. Easiest is past HD 107288 (the bottom corner star) their eerie appearance through small M87 at the west end of the larger V.M87is andonabout1½° to the large lenticular telescopes.Throughbinocularstheytend the brightest galaxy in the Virgo Cluster, galaxies M84 and M86.Ofthetwo,M86 tomergeintoasinglediffuseglow,but and not just from our point of view. This Best deep sky binocular practices These observing tips will well above the horizon, this success using a monopod strap as well, if you use one. help you see more with your usually means reclining or lying while reclining, trapping the far Use averted vision, and be binoculars no matter the quality down. A chaise lounge, sleeping end between my feet. It may patient. Averted vision gives of your skies. bag or blanket thrown over a seem clunky, but it works, as better results the longer you Go high in the sky. When picnic table, or the bonnet of a will a parallelogram mount or do it. This is where all these objects are transiting, you’ll car, or just on a clean, dry patch binocular-go-round. strategies start to reinforce one experience less atmospheric of grass — all of these can serve Be fanatical about dark another: the more comfortable interference. This helps even as observing ‘platforms’. adaptation. Hooded sweatshirts you are, the more likely you’ll under dark skies, but it’s crucial Brace yourself. Or at least help. Pull the hood up around wait long enough for dark if there’s light pollution. brace your binoculars against your face to block incident light. adaptation and averted vision to Get comfortable. For observing something. I’ve had good The hood helps pad the neck really pay off. 60 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 monster elliptical is legitimately huge, with an estimated mass of anywhere from 2 to 200 times that of the Milky Way, and a vast population of 12,000 globular clusters, compared to the Milky Way’s 200 to 300. The other galaxies in this stretch, M8, M89 and M90, are all about one magnitude dimmer. They’re a varied bunch: M58 is a barred spiral; M89 is an elliptical; and M90 is a peculiar spiral with diminished spiral arms but a recent burst of star formation in its core. Of these three, I find M58 the most challenging, as I sometimes struggle to separate the glowofthegalaxyfromthelightofthe 8th-magnitudestarjusttothewest. About 1° and 1.5° east of M58 lie the large elliptical galaxies M9 and M60. M59 is about as bright as M58, but with no nearby bright stars to interfere, it’s a LEACHSID slightlyeasiercatch.M60iseasierstill,at GREY GLOW At magnitude 8.4, M49 might seem an easy target, but its surface brightness is abouthalfamagnitudebrighter.M60is only 13.2. Like many ellipticals, it appears as a subtle, soft patch of light through binoculars. only 5.5° west of Epsilon (ε) Virginis, or Vindemiatrix, the bright star that forms the northern ‘hand’ of the Virgo constellation’s stickfigure. Some observers prefer to ‘drop in’ to the Virgo Cluster from Vindemiatrix—ifyou’reoneofthem,feelfreetorunthrough thisarticleinreverse! ASTRO-PHYSICS Inc. Roughly 1.4° southofM59isRhoVirginis,a 5th-magnitudestaratthetopofanL-shape that extends southwest over about 4°. About a third of the way along the bottom of the L,½° northwest of HD 108985, you’ll find M49, another giant elliptical galaxy. M49 rivals M86 and 6WDWHRIWKHDUWLQVWUXPHQWVIRU M87 in brightness, and each of these large ellipticals forms the gravitational centre of one of the three major galaxy GLVFULPLQDWLQJ$VWURSKRWRJUDKHUV subsystems in the Virgo Cluster. 6%,* &&'¶V $XWRJXLGHUV We have one more Virgo Cluster Messier galaxy to find. If /RVPDQG\0RXQWV you follow the vertical leg of the L asterism from Rho, past HD $VWUR3K\VLFV0RXQWV 108985, and on another 4°, you’ll come to M61, almost exactly 3ODQH:DYH,QVWUXPHQWV halfway between 16 and 17 Virginis. M61 is a face-on spiral, but $OOXQD2SWLFV it contains an active galactic nucleus (AGN) that outshines its %LVTXH3DUDPRXQW0(,, 30; spiral arms, making it fairly easy to detect. 6LULXV2EVHUYDWRULHV That’s the end of the Messier galaxies in the Virgo Cluster, /XQW6RODU7HOHVFRSHV but we’ve really only hit the cluster’s best and brightest. If you &63KRWRPHWU\)LOWHUV get through all of these with binoculars, grab your favourite atlas and see how many of the non-Messier NGC galaxies you Contact ATS can catch. And come back through with a telescope, especially for the ultimate in CCDs to see the barred and grand-design spiral galaxies like M58 Astro-Imaging Gear and M100. There’s a lot to see and to think about in this part of & Integrated Observatories ✦ the sky — now go have fun seeing and thinking! 3K )D[ :HE ZZZDWVFRSHFRPDX Mathew Wedel chronicles his galactic fishing trips at (PDLO VDOHV#DWVFRSHFRPDX 10minuteastronomy.wordpress.com www.skyandtelescope.com.au 61 AS&T Test Report Meade’s 25-cm LX600-ACF Telescope ThevalueoftheLX600comesas muchfromitstimingasfromits advanced technology. DENNISDICICCO ork-mounted Schmidt-Cassegrain telescopes have been around for more than half a century. FThat’s a sobering thought for those of us who vividly remember the first advertisements for them appearing in magazines in the 1960s and their popularity growing almost explosively after Celestron introduced an attractively priced 20-cm model a few years later. By the early ’80s, Meade too was building Schmidt-Cassegrains, and the familiar silhouettes of stubby-tube, fork-mounted telescopes were ubiquitous along the skyline at every star party large and small. Schmidt-Cassegrains were the telescope to own whether your interests lay in visual observing, astrophotography, or both. Frequent improvements, especially ones made for astrophotographers, occurred as Celestron and Meade volleyed design tweaks back and forth vying for market share, all the while keeping the telescopes priced within the reach of many amateurs. Nevertheless, as the 20th century drew to a close and digital imaging replaced traditional film-based astrophotography, Schmidt-Cassegrains surrendered much of their dominance to optical designs, albeit While it has the outward appearance of the fork-mounted Schmidt-Cassegrain telescopes that have served several generations of amateur astronomers, Meade’s new LX600- ACF line has state-of-the-art optics and electronics in a newly engineered telescope and mount that have been designed for deep sky astrophotography. For several months last year the author tested this 25-cm LX600-ACF from the driveway of his ALLPHOTOSBYTHEAUTHOR suburban home. 62 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 expensive ones, better able to cover large digital There’s no question that the ACF optics perform better sensors corner to corner with quality star images. for deep sky photography. Economics played a role, since astrophotographers The LX600 optical-tube assembly (OTA) has an able to afford large-format CCD cameras were also improved mounting system for the primary mirror the ones able to afford expensive telescopes. High- that virtually eliminates image shift as you focus end astrophotography was shifting to an elite group the instrument. And there’s now a very smooth, of individuals who had significant sums to spend dual-speed focuser that aids with critical focusing. on their hobbies. At first blush, it looked like deep But achieving precise focus, which is paramount sky astrophotography’s love affair with Schmidt- for maximum imaging performance, still requires Cassegrains was ending. a delicate touch on the fine-focus knob, and many But times change, and now there are moderately astrophotographers will want to use an optional priced DSLR cameras that perform exceptionally electric focuser (models are available from Meade and well under the night sky. As such, these cameras are other manufacturers). making top-notch, long-exposure astrophotography Tripod, X-Wedge and mount. While outwardly once again something that falls within the budgets similar to other Meade scopes, especially the LX200 of many amateurs. And that’s fueling a market for line, the LX600 is substantially more robust. Simply reasonably priced telescopes that work well for deep put, the 25-cm model I tested is the most stable 25- to sky photography. 30-cm fork-mounted scope I’ve yet reviewed, with the Enter Meade’s new line of 25- to 40-cm LX600 possible exception of Meade’s long-discontinued 30-cm telescopes. Designed specifically for deep sky imaging, RCX400. And stability is what helps make the LX600 the LX600 series is everything that the previous such a successful imaging platform. generation of Schmidt-Cassegrain astrophotographers But there’s a price to pay for this — weight. The dreamed about and then some. And after months of complete telescope setup weighs more than 73 kg, The telescope testing a 25-cm model that we borrowed from the including the 20-kg tripod and optional 12.7-kg breaks down manufacturer for this review, I can confidently say that X-Wedge (a must-have accessory for long-exposure into four major it’s the best telescope of its type that I’ve yet tested for components: astrophotography. a 20-kg tripod, the optional 12.7-kg X-Wedge (shown First, the basics here attached Meade touts “revolutionary new technology” for to the tripod), a its LX600 scopes, but even the newest technology 15.4-kg base with involved — StarLock’s automatic, full-time fork arms, and a autoguiding — is a few years old. But that’s a good 25-kg optical tube assembly (OTA). thing, since it means that it’s innovation that’s already Stripping the survived the test of time. What is new, however, is how OTA of its finder, all this technology is wrapped in updated hardware counterweights designed from the get-go as a platform for long- and StarLock exposure astrophotography. Here’s a quick look at the guide scope reduces its weight LX600’s major features. to 20 kg, but the Optics. Meade avoids calling the LX600 a author still found Schmidt-Cassegrain, using instead the acronym it difficult to ACF for Advanced Coma-Free optics after a change safely assemble the company introduced to the traditional Schmidt- the telescope in equatorial mode Cassegrain optical design more than a decade ago. by himself. In addition to being photographically faster than the original f/10 Schmidt-Cassegrain design (which WHAT WE LIKE: WHAT WE DON’T LIKE: Meade still offers in its other telescope lines), the f/8 ACF produces nice, round star images across full- Solid fork mounting designed Weight requires two people to set up for astrophotography safely frame DSLR cameras. My 2006 review of Meade’s then-new design, which was introduced under the Automatic full-time autoguiding Documentation possibly confusing (StarLock) for beginners moniker RCX but later changed to ACF, included side- by-side comparison images made with 30-cm versions The Autostar II control system’s myriad time-tested features of the original f/10 and new f/8 optical systems. www.skyandtelescope.com.au 63 AS&T Test Report The heavy-duty with the OTA stripped to its minimum configuration X-Wedgegetsa thumbs up for (no finder, StarLock guide scope or counterweights), itsdesignand I struggled to align the safety catches on the OTA’s construction. declination trunnions with their mating pieces on the Ball-bearings and fork tines. It would be easier to do this with the scope large hand knobs on the azimuth set up for altazimuth operation, but with the fork tilted and elevation for astrophotography on the wedge, it’s an intimidating adjustments operation for one person. The real solution is to have a make easy work friend lend a hand when setting up the scope. of precisely Autostar II. The brains for the LX600’s GoTo moving the heavy telescope during pointing (including catalogues containing more than polar alignment. 145,000 celestial objects), tracking and a host of other advanced features are in the Autostar II control system, which has been on Meade’s high-end scopes for In addition to the more than a decade. It is a mature system that works scope’s 25-cm exceptionally well. main aperture Despite its sophistication, Autostar II is relatively and 50-mm finder intuitive and easy to operate in the dark with the hand pointing skyward, control. You don’t need to keep a printed manual at there’s StarLock’s 80-mm f/5 guide hand, since even rarely used features are typically refractor and a accompanied by instructions that scroll across the small-aperture, hand control’s 2-line LED display. There are far too wide-field camera, many Autostar II features to write about here, but you which together can find many of the details in the 72-page LX600 perform a variety of important instruction manual, which can be downloaded as a tasks beyond just PDF file for free from Meade’s website (meade.com). autoguiding the StarLock. This is really amazing technology, and main telescope for it sets the LX600 apart from any other fork-mounted astrophotography. telescope on the market, bar none. In a nutshell, every These include precision centring time you slew the LX600 to a new target, StarLock of celestial automatically acquires a suitable guide star and objects in the begins guiding the telescope accurately enough for field of a camera astrophotography. There is no need for an external or eyepiece, and computer or even so much as a button push of input helping refine the telescope’s polar astrophotography). The OTA and fork mount, without from the user. The system is 100% autonomous. And alignment. the StarLock guide scope and tube counterweights, it’s also non-intrusive, meaning you can go about using tips the scales at almost 36 kilograms. This makes it the telescope any way you want without interference about 30% heavier than Meade’s corresponding 25-cm from StarLock. The autoguiding begins within about LX200 and almost 60% heavier than its 25-cm LX90. a minute of the scope being moved to a new location With StarLock and counterweights, the assembled (by either GoTo slewing or the observer pressing scope weighs close to 41 kilograms. Furthermore, it is the direction buttons on the hand control), and it’s an awkward scope for one person to set up despite four instantly overridden whenever the scope is moved to handles and two handholds on the fork and a single a new position by any means. A single red LED on the handle on the back end of the OTA. StarLock guide scope indicates when the system is To make assembling the scope more manageable, autoguiding and you can begin shooting pictures. Meade has designed a nice system for separating the StarLock also performs a variety of other tasks, OTA and fork arms into pieces that, for the 25-cm, including the precision centring of targets in the weigh 20 and 15.4 kilograms, respectively. This helps, field of an eyepiece or camera; training the periodic but it still makes assembly challenging for one person. error correction (PEC) of the scope’s motor drive; and Indeed, rather than getting bogged down with details, refining the telescope’s polar alignment. I detailed and despite the fact that I set the scope up by myself StarLock’s performance in a review of Meade’s LX850 nearly two dozen times, I will just say that I don’t German equatorial telescopes in 2013, so I won’t recommend it as a safe process for one person. Even rehash that material here other than to say I remain 64 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 As expected, with the telescope only crudely polar aligned, an unguided exposure (left) shows significant image trailing. But with StarLock turned on (right), the tracking was picture perfect. These back-to- back 5-minute exposures of extremely impressed with the system. had a good, but not perfect, track record autoguiding. a globular star I did, however, encounter a few differences this To be fair, any autoguider will struggle under rotten cluster were taken time. Most notably, unlike my previous experience, seeing conditions, so I wasn’t surprised to have a few with a Nikon D700 camera and StarLock did not autoguide flawlessly ‘out of the box’. guiding failures now and then. Barlow lens. I first had to train the PEC and perform what Meade calls an Automatic Rate Calibration (ARC). These steps The takeaway are highly automated, involving only a few button Overall I was very impressed with the LX600. As presses on the hand control and about 15 minutes someone who started doing deep sky photography of time. And since the PEC information is stored in with an 20-cm Schmidt-Cassegrain way back in 1972, the scope’s memory, you only need spend a couple I can tell you that back then the LX600 is what we all of minutes running the ARC during subsequent dreamed a ‘perfect’ astrophotography setup would be observing sessions. In hindsight, it was my experience like, except we never imagined computers controlling with the LX850 that was unusual, since Meade clearly the telescope’s pointing and digital eyes doing the states in the LX600 manual that these steps are “an guiding! essential procedure to obtain peak tracking accuracy”. I can certainly recommend the LX600 to anyone My original StarLock testing with the LX850 who has experience with a fork-mounted Schmidt- was under tranquil summer skies. Under similar Cassegrain telescope, especially one polar-aligned for conditions StarLock performed equally well with the astrophotography. You’ll be right at home with the LX600, but when the frequently turbulent seeing LX600. And because Meade still includes accurate conditions of winter eventually rolled around, StarLock setting circles on the LX600, virtually any method you want to use to polar align the scope will work (something that can’t be said for any of today’s scopes Left: The Autostar II hand that have dispensed with mechanical setting circles). control operates every feature I’d be equally enthusiastic about endorsing the of the LX600 from GoTo LX600 for beginning astrophotographers if the scope’s pointing to the advanced functions of StarLock. Below: documentation was a little better. For example, the The LX600 telescopes can all-important polar-alignment instructions that are be powered by a set of eight mandatory when setting up for astrophotography C batteries (four housed in (the ones that scroll across the hand control), while each fork arm) as well as via a technically correct, are almost physically impossible to conventional 12-volt DC input jack on the scope’s base. do — you can’t point the OTA to declination 90° and A set of fresh batteries will look through the eyepiece while spinning the telescope last for about two nights of ‘rapidly’ on its polar axis. My neck hurts just thinking observing. about it. Nevertheless, beginners have surmounted these obstacles in the past with fork-mounted scopes, and I’m sure they will with the LX600. And when they do, they will be amply rewarded with a robust astrophotography setup that is incredibly powerful. ✦ Dennis di Cicco has been writing about and reviewing astronomical equipment for more than 40 years. www.skyandtelescope.com.au 65 Lunar Imaging IMAGING LUNA 66 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 High-resolution close-ups of the Moon can be a satisfying challenge for modest apertures. ROBERT REEVES unar photography has always been a relatively planetary cameras use fairly large CCD and CMOS simple procedure: aim your telescope, arrays with tiny pixels, often smaller than 3 microns. focus and snap a bunch of pictures. Indeed, These little pixels more than double the resolution over the same basic technique used in 1840 by those old webcams, sometimes eliminating the need for John Draper when he shot the first lunar additional magnification boosts when using telescopes Ldaguerreotype remains essentially unchanged with long focal ratios of f/10 or more. Additionally, these for everyday full-disk images. But taking detailed big detectors enable imaging of much wider swaths of close-ups of crater fields is a different nut to crack. lunar real estate in one shot. Recording sharp lunar images used to require an You can calculate the magnification using this enormous amount of effort and luck. formula: Arcseconds per pixel = (P/FL) × 206.3, Fortunately, with the advent of electronic imaging where P is the pixel size in your camera measured in and frame stacking, that has all changed. These days microns, and FL is the focal length of your telescope in we use the established technique of ‘lucky imaging’ millimetres. — recording a series of images in rapid sequence, and When choosing a camera for high-resolution then combining the sharpest frames into a final, high- lunar imaging, keep in mind that the Moon is resolution result. This enables amateurs with modest predominantly a monochrome object, so a colour equipment to produce lunar images that easily surpass camera is not necessary. Monochrome cameras are the quality of those from professional observatories also more sensitive, enabling you to record at faster from the age of glass plates and film. In this article frame rates than most colour cameras achieve, we’ll take a look at some of the methods that can help particularly at high focal ratios. you get the most out of your equipment and enable you The CMOS and CCD detectors in planetary cameras ZOOMING IN take your own sharp lunar close-ups. are sensitive to ultraviolet and infrared wavelengths. Facing page: When attempting to shoot high-resolution crater These come to focus at slightly different points than High-resolution images, you’ll get more nights of success with a visible light when passed through refractive optics, shots of crater fields, maria mid-size telescope compared to a large one. A 15- to reducing fine detail in your images. So consider and rays are 20-cm aperture will often resolve small lunar features installing an UV/IR filter to block these wavelengths. within most any better than larger instruments — in spite of the fact amateur’s grasp. that resolution increases with aperture. This is due Author Robert to ‘seeing cells’ in the air above you that are relatively Reeves shares his techniques small. A larger telescope will look through multiple to capture sharp cells of turbulent air while a smaller scope might look images like this through just one. one showing Your choice of camera will also influence how Rupes Recta (the you can achieve a high-resolution image. About a Straight Wall). Left: The Moon decade ago, most video cameras popular with lunar is loaded with and planetary imagers had small CCD detectors interesting areas with 6-micron pixels, typically in a 640 by 480 array. great for any These relative large pixels often required additional size telescope, magnification with a Barlow lens to achieve high- such as the oddly elongated resolution images resolving details of 1 arcsecond or crater Schiller smaller, not to mention having to mosaic many images found near the to cover a substantial area of the lunar surface. Today’s ALL COURTESY PHOTOS OF THE AUTHOR southwest limb. www.skyandtelescope.com.au 67 Lunar Imaging MULTI-POINT STACKING atmosphere as ‘seeing’. You can use online weather A relatively new services to get a good idea of what the sky might be program for like before you set up. Watch for the location of the jet stacking lunar stream, a narrow, fast-flowing current in the upper and planetary atmosphere. If the jet stream is passing overhead in images is AutoStakkert! , your area, the seeing will be poor. which includes While you can’t control the atmosphere, you can batch-processing control some of the factors that affect local seeing of multiple videos conditions. The first occurs within the telescope itself: andapowerful allow your optics to cool to the ambient temperature multi-point alignment routine. before beginning to shoot. That way you won’t be looking through the heat rising from your primary mirror or objective lens. The area surrounding your scope is an important consideration too. Avoid setting up on concrete Most planetary cameras or asphalt, which slowly radiate heat for much of include an operating program the night. Avoid shooting over buildings and large and drivers. These generally work structures that emit rising currents of heat at night. well,aslongastheyincludea The altitude of the Moon also affects your images. fewkeyfunctions.Oneofthe The lower the Moon is in the sky, the more atmosphere mostimportantfeaturesisthe lies between it and your telescope. So try to shoot when histogram, which enables you the Moon is high up. Another consequence of increased to monitor the brightness levels air mass at low elevation is atmospheric dispersion. in the video output. Without a The stack of air near the horizon acts like a weak histogramorlevelsgauge,it’sdifficulttoaccurately prism, splitting visual light into its separate colour judge the exposure to avoid overexposing bright areas wavelengths. The higher the Moon’s altitude, the less in the camera’s field. I prefer to control my camera using the free program FireCapture (firecapture.de). Written by planetary imager Torsten Edelmann, this program supports nearly all planetary cameras and includes many features important for lunar, solar and planetary imaging. Besides your telescope and camera, one additional and essential accessory for high-resolution lunar photography is a dual-speed focuser. The stock focusers on most telescopes are adequate for prime-focus imaging, but once you add a Barlow into the mix, you can easily over-shoot optimum focus with just slight turns. Grabbing the focus knob at high magnifications also introduces furious shaking of the field of view, making it nearly impossible to focus the camera precisely. I use a dual-speed Crayford focuser with a 10-to-1 reduction, and I clip a clothespin to the fine- focus knob. This lets me tweak focus by nudging the clothespin with my fingertip, eliminating the vibration induced by grasping the knob. Adding a motorised or electronic focuser is also a good alternative. LUNAR SCOPE You don’t need a big telescope to Beating the seeing take great close-ups of lunar crater fields. Scopes with No matter what telescope or camera you use to shoot apertures of 15 to 20 centimetres will often perform better lunar close-ups, you’ll be at the mercy of something than larger scopes in average seeing conditions. The you have no control over: Earth’s turbulent atmosphere. author records most of his lunar images using this Sky- Watcher 180mm Maksutov-Cassegrain telescope. Astronomers refer to the churning effect of our 68 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 dispersion you’ll record and the sharper your results Now it’s time to record some high-resolution videos. will be. While monitoring the histogram, set the camera’s gain One way to improve your images in unsteady at its midpoint and increase the shutter speed until the seeing is using filters that transmit only the redder right end of the histogram (indicating the brightest wavelengths of the spectrum. Shorter, bluer levels in the video) is just short of the right edge of wavelengths are blurred much more than the longer the graph. Avoid allowing the histogram levels to hit red and near-infrared wavelengths, so a red filter will the right end of the graph, or else you’ll end up with give you the sharpest results in adverse conditions. overexposed regions in your stacked images that can’t be recovered during processing. Capturing videos Itypicallycapturemany3,000-framevideosin SHARPENING Before you start recording lunar close-ups, make AVIformat,whichspanroughly30to50seconds, RINGS sure your optics are properly aligned — collimation dependingonthefocallengthI’vechosen.This Below: Sharpening is critical to getting the best results. If you use a produces 7-gigabyte video with the Celestron Skyris can often result in Schmidt-Cassegrain or Newtonian, be sure to check 236McameraIuse.Besuretohaveplentyofhard- some processing its collimation first. While my Maksutov-Cassegrain drive space, because you’ll record upward of 100 GB of artifacts that need is permanently collimated, my C11 occasionally videos each night! to be corrected. Note the ‘rings’ requires slight adjustments despite being permanently TheMoonmovesacrosstheskyatadifferentrate seen within crater mounted. thanthebackgroundstarsdo,sounlessyourtracking shadows in this Before hitting ‘Record,’ spend a few minutes mountincludesa‘lunarrate’setting,you’llseesome brightened image determiningwhatmagnificationbestsuitsthe imagedriftwhilerecording.Ikeepmyvideosroughly of Rupes Recta conditions for the evening. If the seeing is poor, shoot at on target by placing the cursor on a small crater in the (the Straight Wall). Bottom: Shadows prime focus without any additional magnification. The fieldandthennudgingthedrivecorrectortokeepthe in lunar craters shorter focal length lets you use faster shutter speeds crater centred under the cursor. should appear and capture more frames per second, which ensures blackinyour somesharperframesarerecorded.Iftheseeingisgood, Stacking and sharpening images. If not, addinga1.5× Barlow will resolve more detail. If the Now that you have some quality videos, it’s time to sort you can selectively darken them seeing is great, even stronger amplification can be used. and stack the best frames into single images. This can using the Burn In my experience, shooting at about f/25 is optimal beperformedusingahostofprograms,butIprefer Tool in Adobe during the best seeing. using AutoStakkert! (autostakkert.com)tostackmy Photoshop CC. SUMOFTHEPARTS Stacking hundreds of your best video frames results in a smooth, detailed image ready for additional processing. www.skyandtelescope.com.au 69 Lunar Imaging REAL OR ARTIFACT? you’d like your stacked result to have and the number 00 out Another artifact of frames to stack. I usually stack the best 5 to watch out for in of 3,000 video frames. Although the program has lunar close-ups is a rudimentary sharpening feature, uncheck the false central peaks Sharpened box if you prefer to sharpen the results in small craters. These often using other software. Finally, initiate stacking with the appear in images 3) Stack button. Once your file has been stacked into takeninpoor a single image, the result will appear in a new folder seeing conditions. within the original location of your video files. At this stage, you can move your image into another image-processing program to sharpen the details. If you use RegiStax’s wavelet sharpening, experiment with the slider settings; no two optical systems are videos, and RegiStax (www.astronomie.be/registax)or the same, and what works for one scope-and-camera Adobe Photoshop CC (adobe.com)tosharpenandclean combination might be too much for another. The key up the results. to great high-resolution lunar images is to avoid over- AutoStakkert! is an easy-to-use program that lets sharpening. youprocessmanyvideosinasinglebatch.Tousethe My favourite sharpening tool in AdobePhotoshop program, begin by clicking 1) Open and select your CC is the new Shake Reduction filter, located at Filter first video. Next, under the Image Stabilisation tab, > Sharpen > Shake Reduction. The filter includes selectSurface,andchecktheImprovedTrackingbox. artifact suppression and noise reduction, which Nowclickthe2)Analysebutton,andtheprogram produce results similar to shooting through better will evaluate your video. Once it’s complete, switch to seeing or using a higher-resolution instrument. the screen showing your video, and in the left-hand As with most astrophotos, some additional column, select an alignment point (AP) size — I processing is helpful beyond sharpening. I prefer to do usuallychoose25pixels—andpressthePlaceAP any final processing in Photoshop CC. grid button. This results in thousands of alignment Stacking several hundred frames effectively points. If any points fall in shadowed regions, increase increases the bit depth of the final result, so theMinBrightsettingandclickthePlaceAPgrid AutoStakkert! generates 16-bit TIF, PNG or FIT button again. images with a very high signal-to-noise ratio. Switch back to the control window, and in the This makes it easy to brighten dark areas without StackOptioncolumnontheright,selecttheformat increasing objectionable noise in shadowed regions close to the terminator. I often do this using the Camera Raw filter (Filter > Camera Raw). Finally, I perform any cosmetic cleanup. An unintentional side effect of the stacking and sharpening processes is they can generate artifacts that mimic real detail. Recognising and removing them greatly improves your final result. Using the Burn Tool from the tool palette set to about 5% is the easiest way to darken shadow areas, as well as reduce any ring artifacts along the edge of craters. Use the Eraser or Clone Stamp tools to remove false central peaks in smaller craters, being careful not to eliminate real detail or duplicate an existing feature. By following these tips, exquisitely detailed images of crater fields on the Moon will be within your grasp. SUNSET TERMINATOR Using these tips, you can Relive the most exciting times in space exploration with capture your own high-resolution images of craters like your own telescope and rediscover the joys of lunar the above picture of craters Gutenberg (top) through photography by exploring our neighbouring world. ✦ Gaudibert (lower left). This image was recorded with a Sky-Watcher 180mm Maksutov with a Celestron Skyris 236M CMOS camera. Robert Reeves shoots the Moon at every opportunity from his backyard observatory. 70 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 STAR EXPLORER An all in one computerised telescope system designed for both beginners and advanced users alike. Featuring SKY-WATCHER’s Synscan AZ Goto system coupled with precision mechanics & SKY-WATCHER’s excellent optics. R S: h High Quality Optics h 40 000+ object database h Quick and easy setup, be up and running in minutes. h Easy to use, quick to learn Computerised Goto Telescopes h Brightest Star Alignment 102/1300mm Maksutov-Cassegrain 130/650mm 3DUDEROLF5HƟHFWRU 127/1500mm Maksutov-Cassegrain 114/500mm 3DUDEROLF5HƟHFWRU DISTRIBUTED BY www.tasco.com.au Telescope Workshop Building this 50-cm f/3.9 ball-and-socket telescope took telescope maker Pierre Lemay more than 20 years. The fully assembled instrument tips thescalesat59 kg, including its innovative, dual-axis-drive platform. PIERREIMAGES BY LEMAY A50-cmdream‘ball’scope A 20-year project has produced much more than an alternative Dobsonian. lot of Dobsonian-style telescopes have appeared Isuspecthisdreamisonesharedbyquiteafew in this column over the years, and for good readers. For Pierre, the ‘dream’ includes large aperture Areason. They’re popular because they have the and motorised tracking in an instrument that is potential to deliver plenty of aperture in an effective, comfortabletouseandlightweightenoughtobeeasily simple-to-usepackage.Butanotherdesignthatshares transported and set up. But Pierre’s dream took more theseattributesistheso-calledballscope.Indeed, than20yearstocometrue. but for one significant detail, they would probably be Theprojectbeganin1990whenhesawaclassified morepopularthanDobs.And adfora50-cm,conicalPyrexmirrorblank,which what is that detail? In a word, he duly purchased. “It was a rough cast piece of theball.Moreaboutthatina glassthatneededalotofworkbeforegrinding moment. couldevenbegin,”hesays.Firststopwasalocal The attributes of the tombstone maker’s shop, where a curve of about the ball-and-socket design are correct depth was generated by sandblasting. Next, well demonstrated by this Pierre attacked the rear surface of the blank with a 50-cm,f/3.9reflectorbuilt grindingwheelandjigtothinitandtaketheedge by amateur telescope maker thicknessdownfrom25mmto12mm.Thisreduced Pierre Lemay. He describes themirror’sweightfrom23to14.5kilograms. it as his dream scope, and Additionally,heperforatedthecentreofthemirrorto facilitateitsmountinginthescopelater.Afterthat, Lemay made the scope’s itwassimplyamatterofgrindingandpolishinga hemispheric ‘ball’ using a Styrofoam form, which is shown 50-cm f/3.9 paraboloid! here being shaped with a router Aftertheprimarymirror,thenextbighurdlewas mounted in a jig. fabricating a ‘ball’. This really was the make-or-break 72 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 part of the design. Failing to find a suitable ready- Although lighter than his first attempt, the new made hemisphere, Pierre resigned himself to making hemisphere was still heavier than desired. “I had one, or rather, two. “My first attempt recalls the joke made progress but was still heading for a 45-kg tube about how the operation was a success, but the patient assembly,” he notes. Then inspiration struck. “After died,” he says. “But I learned a lot and developed the carefully considering my options, it dawned on me methods I used in my second try.” that I could lop off part of the hemisphere without To begin, Pierre made a crude sphere by stacking affecting the scope’s motions.” To accomplish this, 5-cm-thick disks of Styrofoam in incrementally Pierre put together another jig to accurately draw varying diameters — like a layer cake. He included a cut line angled 30º from the top of the existing an aluminium plate on the bottom (to support the hemisphere. He made the cut freehand with a jigsaw. mirror cell), and plywood ring on top for attaching As he reports, “It worked — I eliminated 6.3 kilograms the truss poles. Next, he used a router mounted of plastic!” With the two most difficult components in a large, pivoting jig to generate a smooth shape completed, building the rest of the optical tube was from the stair-step layers. The resulting Styrofoam little different from putting together a normal, truss hemisphere would serve merely as a form, over which Dobsonian. Pierre applied car-body filling putty. Once the putty Pierre’s dream scope has a number of nifty hardened, the assembly went back into the jig for more refinements, including a motorised drive and an routing and then sanding. The resulting hemisphere ingenious rotating double-eyepiece turret with helical received eight coats of liquid epoxy resin (sanded focusers. Even so, future modifications are already GARY between each coat) for a smooth, strong finish. All that looming. “I know it’s a cliché, but when I ‘finished’ the SERONIK Experienced remained was to separate the sphere from the form scope two years ago, little did I realise it was only the telescope maker Gary Seronik can by breaking up the Styrofoam. “I was then left with a beginning of the project,” he says. be contacted hollow, 4.8-mm-thick hemisphere weighing about 18 Additional details on the construction of Pierre’s via his website, garyseronik.com kilograms,” he says. scope can be seen at his website: telescopelemay.com ✦ Triple Play On your DDelivvered tablet tto yoour door On your computer Now there are three ways to get Australian Sky and Telescope, including a digital subscription delivered straight to your computer or tablet. Enjoy the same authoritative magazine exactly the way you want it. See more at skyandtelescope.com.au www.skyandtelescope.com.au 73 Astro Calendar galaxies lit up the universe.” “CAASTRO tackles big ‘All-sky’ astronomy questions that can only be answered by observing a large part of the whole southern sky, so broughttolife it’s exciting to be able to use the ‘big sky’ aspect of a planetarium show to tell the public about our work,” said CAASTRO Director, Professor Elaine Sadler. “I hope this planetarium show can convey some of the wonder of the universe we live in, and the big questions that CAASTRO astronomers are JONATHAN NALLY he stars of the astronomy Murchison Widefield Array working to answer.” world (excuse the pun) (MWA) and SkyMapper — and Capturing the Cosmos is narrated Tgathered at the Melbourne demonstrates how CAASTRO by Academy Award-winner Planetarium on March 21 for is bringing together some of Geoffrey Rush, and was officially the launch of Capturing the Australia’s and the world’s best launched on the night by Nobel Cosmos. The result of a two-year astronomers to revolutionise the Prize-winning astronomer and collaboration between Museum way we understand the cosmos. CAASTRO member, Professor Victoria and the ARC Centre of “Each of these telescopes is Brian Schmidt. The show is being Excellence for All-Sky Astrophysics helping us study key aspects of released nationally at the following (CAASTRO), the show paints a our universe,” says Dr Tanya Hill, venues: the Scitech Planetarium picture of how astronomers are Museum Victoria’s astronomer in Perth; the Sir Thomas Brisbane peering back in time to try to work and planetarium manager, and Planetarium in Brisbane; the out how the universe has evolved the show’s writer and director. Queen Victoria Museum and into what we see around us today. “SkyMapper is helping us to Art Gallery Planetarium in Capturing the Cosmos features understand dark energy… [while Launceston; the Wollongong CAASTRO’s cutting-edge research, the] MWA is going to be one of Science Centre and Planetarium; focusing on ‘all-sky’ data collected the first telescopes that can peer Sydney Observatory; and Adelaide from next-generation telescopes across the ‘dark ages’ and help us Planetarium. Make sure you get — in particular, Australia’s understand how the first stars and along and see it. ✦ Royal Astronomical Society of NZ Public Open Nights in Sydney StarFest 2016 Conference August 12–13 October 1–2 May 20–22 The Sutherland Astronomical Society will A weekend of activity at Coonbarabran during Annual meeting of New Zealand’s throw open its observatory’s doors to the the Festival of the Stars astronomers general public. Always a great occasion. starfest.org.au hbastrosoc.org.nz/rasnz-conference-2016/ sasi.net.au VicSouth Desert Spring Star Party South Pacific Star Party National Science Week 2016 May 5–8 August 13–21 October28–November1 Annualstarpartyhostedbythe Various activities around the nation Annualstarpartyhostedbytheastro Astronomical Society of NSW www.scienceweek.net.au societies of Victoria and South Australia asnsw.com/spsp vicsouth.info Siding Spring Open Day Queensland Astrofest October 1 July29–7August Australia’s largest optical telescope throws LionsCampDuckadang,Linville,Qld open its doors to the public. Long-running annual star party starfest.org.au www.qldastrofest.org.au WHAT’S UP? Do you have an event or activity coming up? Email us at [email protected] 74 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 Subscription Offer SPECIAL SUBSCRIBER OFFER IDEALGIFTFORASTRONOMYENTHUSIASTS The benefits of subscribing to Australian Sky & Telescope include: Subscribe or renew your > FREE HOME DELIVERY throughout the year > GREAT GIFT IDEA for beginner astronomers subscription to Australian > SAVE with a 2-year subscription Sky & Telescope and > NEVER MISS an issue receive a FREE DVD: > BE AMONG THE FIRST to receive the magazine > SAVE 10% on DVD/CD and chart purchases from Hubble: 15 Years of Discovery. Australian Sky & Telescope Call now (02) 9439 1955 MAGAZINE $140: Two years – 16 issues PLUS DVD $76: One year – 8 issues PLUS DVD. 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Russell used a 30-cm Newtonian on an equatorial mount, QHY-22M camera plus H-alpha and OIII filters, for a total of four hours of exposure. How to submit your images Images should be sent electronically and in high-resolution (up to 10MB per email) to [email protected]. Please provide full details for each image, eg. date and time taken; telescope and/or lens; mount; imaging equipment type and model; filter (if used); exposure or integration time; and any software processing employed. If your image is published in this Gallery, you'll receive a 3-issue subscription or renewal to the magazine. 76 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 ▴ VALENTINE’S VENUS Troy Shiels Venus (and Mercury) shone brilliantly in the skies over Sydney on Valentine’s Day. Troy used a tripod-mounted Nikon D40 and Nikkor AF-S DX 18-55mm lens to take two images (each 15 seconds, f4.8, ISO1600), stitched together with Image Composite Editor. ◀ RUNNING MAN Stephen Chadwick Not far from the Orion Nebula lies the Running Man Nebula, also known as Sharpless 279 and NGC 1973/1975/1977. Stephen used a 35-cm Newtonian, QSI 683wsg camera and LRGB filters for a total exposure time of 18 hours (L: 6 hours; R, G and B: 4 hours each). www.skyandtelescope.com.au 77 Gallery ◀ GREEN CHEESE Brett Henry Showing just what you can do with a smartphone (see page 38), Brett used an iPhone 6 Plus held by hand to an 8-mm Ethos eyepiece on a 50- cm SDM reflector. Oh, and a Moon filter, which is why our celestial neighbour looks green. ▶ THE GREAT NEBULA Florin Zaharia A delicious summertime sight, the Great Nebula in Orion is always a firm favourite. Florin used a William Optics 110FLT plus focal reducer/ field flattener, light pollution filter, ATIK 460Ex mono camera and ATIK EFW2 filter wheel with LRGB filters, for a total exposure time of 1 hour and 43 minutes. 78 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 Market Place REPAIRS TO ALL NEW Your essential source OR ANTIQUE .COM.AU for astronomical products OPTICAL EQUIPMENT Australia’s Favourite Optics Retailer and services Telescopes - Binoculars - Microscopes - Accessories Waterproof 2.3m, 3.5m, 5.0m & 6.7m Complete Observatories. www.siriusobservatories.com Free DVD (while stocks last) [email protected] Designed & Manufactured in Australia and shipped to anywhere in the world!! 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The charts Members have a water-resistant laminate coat to 2 June Did you know you can get a subscription make them more to AS&T by being a member of an durable when used astronomy club? Subscribers also get outside. An additional 10% off charts, DVDs etc from AS&T. reference guide provides an overall Contact your club or subscribe direct to view of all 18 charts and an index to the Australian Sky & Telescope. constellations and major stars. $19.95 Tel: (02) 43 1 55 [email protected] Order by ringing (02) 9439 1955 with your credit card details, or fill in the order form on page 75 and post or fax it back to us. The nebula wars More than a century ago, it defied belief that small scopes could image big nebulae best. Is red light best? Skygazers often use red light to protect their night vision, but is red really the ideal colour? 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The user friendly menu system allows ly or electronically in either axis without the mount automatic slewing to over 42,900 night losing its alignmentm or positional information. sky objects. Even an inexperienced After moving to a new object, the mount astronomer can master its variety of will continue to track it accurately. This features in a few observing sessions. gives the user enormous freedom, FRQYHQLHQFH DQG ƜH[LELOLW\ during observational sessions. Focal Point Plutoisnottheend It’s dangerous for NASA officials to imply we’re done exploring the Solar System. EMILY LAKDAWALLA hen New Horizons flew Then, of course, the discovery of Kuiper Belt objects look? Pluto is not past Pluto last year, NASA largeKuiperBeltbodiesunseated the end of the Solar System; it’s just WAdministrator Charles Bolden Pluto from planethood. We now know the beginning of the rest of the Solar heralded it as “the capstone event to 50 of thousands of Solar System objects System. The Kuiper Belt — contrary to years of planetary exploration,” adding beyond Neptune. Hundreds of them what Grunsfeld said — remains almost that the Pluto encounter “completed are large enough to be round, and their entirely terra incognita. the initial survey of our Solar System.” varying colours and albedos suggest that Even within Neptune’s orbit there NASA’s science chief John Grunsfeld they’re at least as diverse as the moons exist worlds we’ve barely touched. We said, “There’s very little terra incognita orbiting the giant planets. now understand Uranus and Neptune to in our Solar System today.” These In fact, this ‘third zone’ of the Solar be a distinct class of planets from Jupiter statements arise from an outdated view System is almost certainly stranger and Saturn, and they have changed in the of our celestial neighbourhood — the than anything we’ve seen before. New quarter century since we visited them. hierarchical view of nine planets, with Horizons’ flyby of Pluto and Charon We need to orbit our ice giants, probe Pluto at the outer end, accompanied by a revealed bodies more varied than anyone them and understand what they can tell smatteringofless-importantbodies— had imagined. How weird do the other us about similar-sized exoplanets. andtheythreatenthefutureofNASA’s As for those enticing moons, Solar System exploration. Voyager 2 managed only very distant, How outdated? For starters, the low-resolution views of Uranus’ moons; Voyager encounters with the outer planets “Pluto is not the Charon’s surprisingly youthful surface revealed the diversity and activity of their end of the Solar makes me wonder how most of them moons, many of them larger and more truly look. And we don’t know how time recently active than some planets. Among System; it’s just the changes the appearances of these active, them are Europa, Enceladus, Titan and planet-circling worlds — Triton, Titan, Triton—eachofthemasworthyofa beginning of the rest Enceladus, Io, and possibly Europa. dedicated mission as any of the planets. of the Solar System.” We have never visited any of the icy Trojans and Centaurs, populations roughly as numerous as the main belt asteroids. Finally, missions such as Rosetta and Hayabusa have shown us the dynamic nature of the Solar System’s tiniest bodies, and we’ll likely never finish our reconnaissance of all of them. Each time we step a little farther into space, we see more, ask new questions, have new destinations to travel to. But it’s a constant struggle to win support for funding for robotic exploration beyond Earth. So to have space science leaders imply that our work to explore the Solar System is in any sense complete is hazardous. We’re not done with the Solar System. There’s so much more to explore. ✦ Emily Lakdawalla is Senior Editor and -CALTECH PYLE / T. (SSC) Planetary Evangelist for The Planetary Society, blogging robotic Solar System Artist’s concept of the view from a Kuiper Belt body, looking back towards the Sun. NASA / JPL exploration at planetary.org 82 AUSTRALIAN SKY & TELESCOPE MAY | JUNE 2016 SKYWATCHER’S ULTIMATE TELESCOPES ESPRIT 3 ELEMENT ED APOCHROMATIC REFRACTORS ED Triplet APO Refractor was designed by Sky-Watcher with astro-imagers in mind! The air-spaced ED APO optics are fully multi-coated for extra clarity, contrast, and protection. Designed for the most demanding Astrophotographer, but also delivering exceptional visual observing. The two-element feld ÀDWWHQHUZKLFKFRPHVVWDQGDUGZLWKWKH6N\:DWFKHU Esprit, will ensure pin point stars across the entire focal plane. 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