The Urban Astronomer's Guide. A Walking Tour of the Cosmos for City Sky Watchers PDF
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The Urban Astronomer’s Guide A Walking Tour of the Cosmos for City Sky Watchers Rod Mollise RodMollise Mobile,AL,USA BritishLibraryCataloguinginPublicationData AcataloguerecordforthisbookisavailablefromtheBritishLibrary LibraryofCongressControlNumber:2005932858 PatrickMoore’sPracticalAstronomySeriesISSN1617-7185 eISBN:1-84628-217-9 ISBN-10:1-84628-216-0 ISBN-13:978-1-84628-216-4 Printedonacid-freepaper ©Springer-VerlagLondonLimited2006 Apartfromanyfairdealingforthepurposesofresearchorprivatestudy,orcriticismorreview,aspermitted undertheCopyright,DesignsandPatentsAct1988,thispublicationmayonlybereproduced,storedor transmitted,inanyformorbyanymeans,withthepriorpermissioninwritingofthepublishers,orin thecaseofreprographicreproductioninaccordancewiththetermsoflicencesissuedbytheCopyright LicensingAgency.Enquiriesconcerningreproductionoutsidethosetermsshouldbesenttothepublishers. Theuseofregisterednames,trademarks,etc.inthispublicationdoesnotimply,evenintheabsenceofa specificstatement,thatsuchnamesareexemptfromtherelevantlawsandregulationsandthereforefree forgeneraluse. Thepublishermakesnorepresentation,expressorimplied,withregardtotheaccuracyoftheinformation containedinthisbookandcannotacceptanylegalresponsibilityorliabilityforanyerrorsoromissions thatmaybemade. PrintedinSingapore/KYO 9 8 7 6 5 4 3 2 1 SpringerScience+BusinessMedia springer.com Contents Introduction .................................................... vii PartI:TelescopesandTechniques 1 TheWhysandHowsofUrbanObserving ............................ 3 2 TelescopesforUrbanObservers.................................... 13 3 AccessoriesforUrbanObservers ................................... 37 4 UrbanObservingTechniquesandProjects ........................... 53 5 UrbanObservingPrograms....................................... 69 PartII:AWalkingTouroftheCosmos 6 Spring ........................................................ 93 Tour1 BurningHeartoftheHuntingDogs,M94,M51, andCompany............................................ 93 Tour2 Lion’sDen............................................... 104 Tour3 TheTressesofBerenice..................................... 113 Tour4 IntheArmsoftheMaiden .................................. 124 7 Summer ...................................................... 135 Tour1 TheFriendlyStars......................................... 135 Tour2 ArkenstoneintheStars..................................... 145 Tour3 StarNestsinCygnus....................................... 153 Tour4 RequiemfortheDeadStars ................................. 161 8 Autumn....................................................... 169 Tour1 ATrioofFallGlobulars..................................... 169 Tour2 TitanandCrab ........................................... 177 Tour3 TheCassiopeiaClusters .................................... 187 Tour4 DeepWaterConstellations.................................. 195 9 Winter........................................................ 201 Tour1 M78:ReturnoftheHunter.................................. 201 v vi Contents Tour2 ChallengesforDeepWinterNights ........................... 210 Tour3 ASurprisePlanetary....................................... 216 Tour4 Winter’sEskimo .......................................... 223 Tour5 OnefortheRoad.......................................... 230 Appendix1:InternetResources ...................................... 237 Appendix2:FindingDirectionsintheSky ............................. 239 Appendix3:ObjectClassificationsandDescriptions ..................... 241 Appendix4:TheUrbanAstronomer’sGuide:CompleteListofObjects ....... 245 Index .......................................................... 251 Introduction The Urban Astronomer’s Guide is the result of a crazy idea for a book that came to me nearly twenty years ago. I knew deep sky objects—nebulae, star clusters, and galaxies—couldbeseenfromthecity.Plentyofamateurastronomerswerebraving countless streetlights in search of distant marvels. But there was little written in- formationavailableonviewingthedeepskyfromurbanandheavilylight-polluted suburbanlocations.TheonlymentionofthesubjectIfoundinastronomybooksand magazineswasthesternwarningthatitwasimpossibletogetagoodlookatanything other than the Moon and planets from urban locales. I knew this wasn’t true—I’d observedtheentireMessierlistfrommybrightbackyardandhadalotoffundoing it.Iwassuremanymoreamateurastronomers“trapped”amidcitylightswouldalso lovetoseedeepskywondersfromhome—ifonlytheyhadalittleinformationand encouragement.Solution?Thebookyouholdinyourhands. Ispentmany,manyhoursobservingtheobjectsthatformtheskytoursincluded inthisguide.Butthatwastheenjoyablepartoftheproject.Thehardworkwasdone bymyfriendandfellowobserver,PatRochford,andbymydearwife,Dorothy.They didn’tsharemuchoftheobservingfun;insteadtheydevotedthemselvestothetasks ofcheckingthemanuscript,and,mostimportantly,providingtheencouragementI neededtokeepgoingwithwhatsomepeopletoldmewasan“impossible”concept forabook.Thanksarealsodue—inspades—toJohnWatson.JustwhenIwasready totossthisideaaside,he,likePatandDorothy,keptmeontrack.Dorothy,Pat,and John—thisoneisforyou. RodMollise SelmaStreet Summer,2005 vii PART I Telescopes and Techniques CHAPTER ONE The Whys and Hows of Urban Observing Have you gone out into your backyard or garden and looked up at the night sky lately? If you’re a seasoned amateur astronomer living in the city, especially an as- tronomerinterestedinthedeepsky,theuniverseofobjectsbeyondtheSolarSystem, youprobablyhaven’t.Theconventionalwisdomisthatthequarrydeepskyobservers hunt—starclusters,galaxies,andnebulae—doesn’tshowupwell,oratall,fromthe typicalsodium-streetlight-pinkurbansky.Everyveterancity-boundamateurprob- ably spent some time observing from home as a novice when every night was an adventureandnotasinglecleareveningwastobewasted.Butwithexperienceand agrowingorientationtowarddeepspace,mostcitydwellingastronomerseventually desertthebackyardforoccasionaltripstodarkerlocales—anastronomyclub“dark site,”afriend’svacationhomeorfarm,oranorganizedstarparty. Tripstodarksitesaregreat,butwouldn’tyouliketogetoutwithyourwonderful telescope more often? That’s what this book is all about. Whether you’re a novice amateur or a deep sky veteran, it will show you how to enjoy night after night of wonderfulsightsfromthecomfortofhome.There’sanamazingamounttobeseen, evenunderthebrightestskies.WhatIamgoingtodoistakeyouonawalkingtourof thecosmos.We’lltravelfromdepressingcitylightstothewondersofdeepspace.You’ll learnwhatyouneedtopackforthesehikes,what’stobeseenoutthere,andhowbest toseeit.Thebulkofthebookconsistsofready-madeseasonaltoursoftheheavens, butyou’llalsolearnhowtoplanyourownnightskyjourneys.Beforeconsideringthe “how”ofurbanamateurastronomy,though,let’stalkmoreaboutthe“why.” Yes,observingfromperfectcountryskiesiswonderful,butanemphasisondarksite observingcomesatapricefortheurban-dwellingamateur:ifyourelyonlyonthese opportunities, you’ll usually wind-up observing once a month—if that frequently. “Onceamonth”isafarcryfromthe“everyclearnight”ofnovicedays,butfortoday’s amateurthat’softenasgoodasitgets.Organizedclubstarpartiesareusuallyconfined 3 4 The Urban Astronomer’s Guide toweekendsclosesttothenewMoon,and,whileanindividualwithapersonaldark site can theoretically get out deep sky observing more often than that, the facts of modern life—two career families and long workdays—tend to rein things back to once-a-month.Distanceisanothercomplicationthatcutsthefrequencyofobserving runsfortheurbanastronomer.Gettingtodarkskiesmeansdriving40–60milesfrom thecenterofevenamediumsizedcity.Ifyouhavetotravelanhourortwo,setupthe scope,andthenallowtimefortearingthingsdown,packingandreturninghome,you arenotgoingtobedoingmuchweeknightobserving.Thisonceamonthsyndrome (whichmaybereducedto“everycoupleofmonths”duetopoorweather)meansthat theurbandeepskyobserverisusuallybadlyoutofpractice. Beinglostinspaceisafeelingwellknowntothecity-basedastronomer.It’sbeen a couple of months since you were last out observing at the club observatory, and, eventhen,youdidn’tseemuchsincetheNewMooncameonapartlycloudyevening. Tonight is different. You’re at the Texas Star Party, your yearly getaway under the superblybrightstarsanddarkskiesoftheSouthwestU.S.desert.Notalightinsight. Velvety blackness and stars everywhere. And there you stand, not quite feeling in harmonywiththecosmos.Thetelescopethatwassoeasytoassembleinyouractive novice days now seems slightly puzzling. Where do you insert the bolts that attach thetripodtothemount?Whatwasthatquick-and-accuratepolaralignmentmethod thatonceseemedsoeasy?Naturally,theconstellations,withtheirscadsofstarsvisible indarkskies,lookalittleunfamiliar,butgettingorientedwouldbeeasierifyouat least remembered which bright star was which. If that weren’t bad enough, when the telescope is finally assembled and aligned, objects that once looked spectacular don’tseemtoshowasmuchdetailastheydidinthepast.Youalmostfeelasifyou’ve forgottenhowtoobserve.Youhave. SirWilliamHerschel,arguablythegreatestamateurastronomerofalltimeanda professionalmusician,oftenlikenedobservingwithatelescopetoplayingamusical instrument,andwasoftheopinionthatastronomicalobserving,likemusic,requires constantpractice.Ifyou’veexperiencedtheabovelostinspacefeeling,youknowSir Williamwasright.Observingisacomplexseriesoftasks,fromgatheringequipment fortheevening’srun,todevelopingalistofobservingtargets,togettingthebestview ofagalaxy.Withoutconstantrepetitiontheseskillsgrowrusty.Howgoodareyouat anycomplicatedtaskyouonlyperformonceeverymonthortwo? What’stheanswer?Itwouldbeniceifweallenjoyeddarkskiesfromhome,but lightpollutionisnotgoingawaytomorrow.Manydedicatedamateurandprofessional astronomersareworkingtoreducethiscurseofmoderntimes,butit’sunlikelythat theaverageurbanamateur’sskiesaregoingtogetbetteranytimesoon.Theanswer forthecityobserverissimpleandliescloseathand:despitebrightskies,observeevery clear night. From the backyard, the rooftop, the secure park, the science museum parkinglot,oranyplaceinthecitywherethere’sanopenviewoftheskyfromsafe surroundings. What Can You See from the City? “Well,that’sOKfortheSolarSystemboys.Theycandowelldowntown.Youdon’t needdarkskiestoviewJupiter,Saturn,ortheMoon,butIdon’tcareaboutthatstuff. The Whys and Hows of Urban Observing 5 Iwanttoobservethedeepsky,andyouhavetohaveadarksitetoseeanythingbeyond a few of the very brightest objects.” Wrong. There’s a lot to be seen by the patient, educateddeep-skyobserverfromalmostanyurbansite,including: (cid:1) TheentireMessierlist,evenM74,M33,M76,andM97,thesupposed“hardones.” (cid:1) ManyNGCobjects,andnotjustopenstarclusters,thoughyoucanfeastonasmany ofthoseasyoudesire. (cid:1) Supernovaeburningintheheartsofdistantgalaxies. (cid:1) Thebeautyoftheclassicalconstellationsintheirstatelymarchacrosstheskyasthe seasonschange. (cid:1) Thecomingsandgoingsofthoseintergalactictramps,thecomets. (cid:1) HordesofasteroidstracingtheirlonelypathsthroughtheSolarSystem. (cid:1) Theanimalsthatformoururbanecosystemandsurviveunnoticedunderthefoot ofMan. (cid:1) Thelooksofwonderonthefacesoffamily,neighbors,andfriendsasyoushowthem skymarvelsfromthefriendlysurroundingsofhome. Come join me on a typical city evening’s observing adventure. Tonight, my in- strument of choice is my “big” scope, an inexpensive Meade 12.5-inch Dobsonian reflector.Dependingonmygoals,Imighthavechosenan80-mmshort-tuberefrac- tor, a Celestron Nexstar 11 Schmidt Cassegrain telescope (SCT), or just a pair of binoculars.Onthiseveningthe12.5-inchscopeisappropriatebecause,inadditionto observingsomeMessiergalaxies,I’llbesearchingforasupernova,anagedandobese starthat’sendingitslifeinaspectacularexplosionneartheheartofadistantgalaxy. The12.5-inchtelescopeprovidesgenerousapertureforsupernovahunting,anditis alsosurprisinglyeasytosetup.Icarryits“rocker-box”mountoutside,plunkitdown, manhandlethetubeoutthebackdoorandontotherockerboxandI’mreadytogo. Withthescopeassembled,Iturntotheevening’sobservinglist.Somefellowam- ateursfinditamusingthatIgotothetroubleofdrawingupdetailedlistsandcharts foraninformalpeekattheskyfrommybackyard.But,intruth,detailedplanningis probablymoreimportantfortheurbanastronomerthanforthoseblessedwithdark skies.Iftheskyisclear,countryastronomerscanturntheirscopestoanyquarterof theheavensandberewarded.Weurbanobservershavetobemorediscriminating. Beforesettingthescopeup,IhadalookatthevirtualskywiththeaidofSkytools2,a computerizedastronomyplanningandchartingprogramthatrunsonmyPC.Iused ittohelpmeselectinterestingobjectsnearingthemeridianformydateandtime— objects as high in the sky as they’d ever get for my location. This selection process allowsmetoescapesomeoftheworsteffectsoflightpollutionnearthehorizons. Astheskydarkensandenfoldsmeandmybelovedtelescope,Ibegintogetinto the rhythm of sky and land. Sure, if I concentrate I can hear traffic on the busy thoroughfare just two blocks away, but my mind filters that out. I only hear the comfortingchirpofcrickets,smellthespringsmellsofgardengreeneryonthewarm air,andseetheinvitingglimmerofthefirststarstogracetheeveningsky.Thesky itself?Oh,it’snotpristine.Farfromit.Thehorizonsareringedbythegaudypinkof countlesssodiumarcstreetlights.Evenonacrispwinternighttheshortexposureof OrioninPlate1isobviouslyfoggedduetoheavyskyglow.Conditionsareevenworse tonight in the hazy atmosphere of spring. But the great constellation Leo is riding
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