1914ApJ 39. . 37 3B VOLUME XXXIXJUNE1914NUMBER5 VISUAL OBSERVATIONSOFHALLEY'SCOMETIN1910 is safetosaythatitdidnotgiveusanynewinformationconcerning nomena presentedbyothercometsofrecentyearswhichatmost in itsactiononthesensitiveplate,andtherewerefewornoneof return in1910,thoughabrilliantandinterestingobjecttothenaked only attainedthefaintestnaked-eyevisibihty,Halley'scometatits bodies. Whileitlackedmuchininterestas seen withtheeyeof eye—especially inthemonthofMay—was,nevertheless,adis- , madeit,atitsreturnof1910,perhaps themostinteresting which, addedtoitslonglife-historyofmore thantwothousand have putHalley'scometinthefirstrankamong therecordsofthese comets, however,thenumerousphotographs obtained ofitwould visibility foracoupleofdays.Haditnotbeen fortheprevious by Morehouse'scometof1908,whichjust attainednaked-eye which wasfaintlyvisibletothenakedeyeforaboutoneday,and these strangebodies.Photographically,itslightwasrelativelyslow appointment whenconsideredfromaphotographicstandpoint.It comet ofhistory.The apparentlengthofitstailwhennearestthe the remarkablephenomenashownbyBrooks'scometof1893, the sensitiveplate,tohumaneyeitleft alastingimpression ASTROPHYSICAL JOURNAL © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem AN INTERNATIONALREVIEWOFSPECTROSCOPY Considering itsgreatbrightness,andtheextraordinaryphe- AND ASTRONOMICALPHYSICS By E.BARNARD THE 373 1914ApJ 39. . 37 3B 1 374 As seenfromthisobservatoryitwasvisibletothenakedeye eaTth (i20°ormore)wasprobablythegreatestonrecord,though April 29toJune11,whichwasnotanexcessivedurationofvisibility. the actuallengthwasmuchexceededbymanypreviouscomets. side ofthisreturnHalley’scomet. has beenexceededbyseveralcometsthatneverattainednaked- With the40-inchtelescopeitsvisualappearanceextendedfrom eye visibility. September 15,1909,toMay23,1911,which,thoughalongperiod, descriptions ofitsappearanceinearliertimes.Itwasunfortunate, fact thatthegeneralimpressionleftbysuchreportswouldbe degrees long{MonthlyNotices25,220).Ifind,however, thatthisgreatlengthis mysterious objectstretchingitswonderfulstreamoffightacross simply aprinter’serrorof150degreesfor15degrees. SeeanotebyElleryin which theaverageastronomerregardedit.Thiswas,atleast, everyone whosawthiswonderfulobjectitwiththesamespirit sentimental side.Itwouldhavebeenagratificationtoknowthat exceedingly misleadingwhencomparingthepresentreturnwith were sogreatlydisappointedinthecomet—^unfortunatefrom feeling ofthepresentwriterwhenhelookedatthisbeautifuland of elationandwonder—onewouldalmostsayveneration—with also, fromthefurtherfactthatevenastronomerssometimeshavea southern observers. he givesthelengthas15or16degrees.Thissmaller length isverifiedbyother The newspapershadexcitedthepublicpulsetoahighpitchby glory whenseenbydwellersinandnearthecentersofpopulation. Astronomische Nachrichten,64,219(samedateastheone in MonthlyNotices),where what itwouldlooklike,andhadthusraisedexpectation beyondall glowing andsensationalaccountsofwhatthecometwoulddo and electricfightsoftodaycompletelyrobbedthecometits reason. Whentheseexpectationsfailed,purely becauseoflocal the sky. } © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem 1 In thisplaceitmaybewelltosayawordortwoonthepopular It isunfortunatethatthenewspapersandgeneralpublic The greatcitiesthathavegrownupsince1835,andthesmoke AccordingtoEllery,cometI1865,forseveraldaysinJanuary, hadatail150 halley’s cometfromapopularpointofview E. BARNARD 1914ApJ 39. . 37 3B u saw it.Thewriterwasstronglyimbuedwith thisthoughton several nightswhileobservingHalley’scomet wheninitsmost of thesedreadbodieswasunknown,andwhen everythinginnature understand howterrifyingthecometmusthavebeeninformer should inspire,attheleast,anuneasinessin mindsofthosewho fitted eithertoimpressorterrifytheobserver,justashismental pressed withamysterythatisnotpresentintheday,comet, in thetailsofsomecomets. there islittlewonderthattheunheraldedadvent ofagreatcomet seemed topossessaspiritforgoodorevil—and mostlyforevil— temperament mightsuggest.IntheDarkAges, whenthemission with itsweirdstreameroffightreachingfarintospace,waswell In thecalmofspringnight,atatimewhenoneiseasilyim- who hadpaintedinrathervividlanguagethedirefuleffectsof papers) tokeepoutthedeadlycometgases,manufacture breathing thedeadlycyanogengas,whichhadbeenshowntoexist were supposedtowardofftheevileffectsofcomet. and sale,amongthenegroesofSouth,cometpills,”which making anyprediction,itfarexceededthemostsanguineexpecta- parison atfuturereturns,itwouldindeedbeunfortunate.In upon thecometandheadsofthosewhohadmadenopre- its bestatthereturnof1910,andwhowouldhavebeenjustifiedin reality, tothosewhounderfavorableconditionssawthecometat Were suchrecordsasthesetheonlyonestodependuponforcom- times, evenifitsdisplaythenwasnomorestrikingthanin1910. tious andunwarrantedstatementsofoneortwomenscience dead inthehumanbreast.Casesofthiskinddevelopedallover cracks indoorsandwindowsChicago(accordingtothedaily startling vividness.Itshowedthatthesuperstitiousterrorfor- diction whateverastowhatthecometmightreallylooklike. conditions, itwasnotpossibleforthemtopileenoughcontumely this countryandabroád—fromthestopping-upofkeyholes merly attendingtheappearanceofagreatcometisbynomeans tions intheremarkabledisplayitpresentedtous. © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem The “cometgas”scareseemedtobedirectlyduetheincau- Such beingthecaseinourpresentenlightenedday,itiseasyto There wasonefactwhichbroughtforthbythecometwith VISUAL OBSERVATIONSOFBALLETSCOMET 375 1914ApJ 39. . 37 3B 0 POSSIBLE ENCOUNTEROFTHEEARTHWITHTAILCOMET impressive stage,anditwouldnothavetakenmuchimaginationto one ofthebranchestail—thesouthernbranch—on,orabout, it seemsmorethanprobablethattheearthactuallydidencounter or closelyfollowing,thetimecomettransitedsun.Indeed, of today,however,onecouldseenothinginitthatwoulddisquiet have endoweditwithaguidingspirit.Withtheenlightenment on ouratmospherewasapparentformonthsafterward. May 18or19,andmoreprobablyonthelaterdate.Thereisalso on theprobableencounterofearthwithaportiontailat, a suspicionthattheinfluenceofthisencounter(ifsuchtherewas) or terrify,butratherthatwhichraisedasenseofextremepleasure 376 lower, andprobablylargerbranchofwhichwidenedtowardthe approach totheearth,itmaybeappropriateaddsomeremarks and wonderatthemagnificentmysteryitpresented. Amherst (whoseobservationseemedtoreferMay16),Ihave its length(54)wasover30millionmiles,ortwicethedistanceof earth. Therearestrongchancesthattheearthpassedthrough diagram onp.389,andwithoutdoubtextendedbeyondthe York CityandanewspaperaccountbyProfessorD.P.Toddof the cometatitsnearestapproachtousonMay18. southeast horizon,involvedtheecliptic,aswillbeseenby to reachtheearthisshownbyfactthataslateMay25 location amongthestarsonthesetwodates. Theheadofthe perhaps 10degreeswide.InPlateXIhave triedtoshowas seen noreferencefromnorthernobserverstothesecond,fainter this partofthetailaboutMay19.Thatwaslongenough the brightbeamandseparatedfromitbya distinctdarkspace overlooked byobserversintheNorthernHemisphere. Itis,how- and broadertailshowninmydrawingsofMay1718south accurately aspossibletheappearanceof tails andtheirexact comet was,ofcourse,invisiblebelowthehorizon. Thisfeature (the broad,faint,southerntail)seemsto have beengenerally © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem In connectionwiththisaccountofHalley’scometanditsnear The doubletailseenhereonthenightsofMay17and18, With theexceptionofasketchbyMissMaryProctorinNew E. BARNARD 1914ApJ 39. . 37 3B others attheTransvaalObservatory(nowUnionObservatory). ever, wellshownindrawingsmadeSouthAfricabyInnésand Bahia Blanca,ArgentineRepublic,onMay19,1910,at5a.m. drawing madebyDr.FrankC.Cook,UnitedStatesNavy,at See Circularsjandiiofthatobservatory.Itisalsoshownina In theSouthAfricansketchessouthtailisgenerallyshown light, whichfillsoutthespacetosoutheasthorizon. mined, butthesouthedgeofitisevidentlylostinzodiacal In mydrawingsthenorthedgeofsouthbranchiswelldeter- fainter andverymuchbroader,whichagreeswithmydrawings. Journal, 26,145). attention toanddescribesthissecondbroadertail{Astronomical none greaterthantheuncertaintyofdrawingsthemselves. the tailonMay17and18.AcomparisonofSouthAfrican by thenotes,skywasnormal.Itisprobablethatslight drawings withmine,however,doesnotshowanyparallax,atleast mistiness mentionedonthatdatewasinnowayconnectedwith out oftheordinary,andcertainlyhadnothingtodowith comet. Inthelatterpartofnight,whenmoonhadset, the presenceofcomet.Theslightaurora,also,wasnothing branch seemedtospreaditseffectoverthesoutheasthorizon,but of thecomet’stail.Atsametimesouthernandfainter the skyseemedtobefreefromanydecidedmistinessnorth on thecloudsinsouth.This,combinedwith thegeneraleffect appearance ofthecloudsnearsunanda barofprismaticfight were verysuggestive{AstronomischeNachrichten,185,229,1910). there wasnothingespeciallysuggestiveinitsappearance. of theskyandclouds—forentirehad a mostunnaturaland Briefly, theseconsistedofapeculiariridescenceandunnatural time thanwhenonewaslookingforsomething outoftheordinary. but nothingunusualhadappeareduntilclose tonoon,whenthe The skyhadbeenwatchedcarefullyduringthe forenoonofthisdate wild look—wouldhaveattractedmarkedattention atanyother © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Professor C.D.Perrine,atCordoba,ArgentineRepublic,calls One wouldhaveexpectedconsiderableparallaxinportionsof During thefirstpartofnightMay18,aswillbeseen The forenoonofMay19,however,developedpecuharitiesthat VISUAL OBSERVATIONSOFBALLETSCOMET 377 1914ApJ 39. . 37 3B interesting ifithadbeenpossibletofollowthe cometcloselywith posterity. TheseobservationsbyMr.Backhouse werenotknown a recordshouldbemadehereofthephenomenon forthebenefitof a similarnaturetothoseseenhereinthefallof1910.Itisprobable, to mewhenmypaperwaspreparedforthePhilosophical Society. the closeapproachtousoftailHalley’scomet. Nevertheless, Hendon HouseObservatory,No.2,p.109,1902).Mr.Backhouse’s descriptions showthatthephenomenaseenbyhimwereperhapsof land, England,throughmanyyears(seePublicationsofWest therefore, thatthisluminoushazewasinnowayconnectedwith which Iwasalmostconstantlyoutatnightcomet-seeking. a similarphenomenonwasrecordedbyMr.BackhouseatSunder- Halley’s comettotheearthwereitnotforfactthatapparently luminous hazehadsomeconnectionwiththenearapproachof by meinpastyearspreviousto1910—-especiallythose Apparently nothingofthekindhasagainbeenvisibleheresince during thesameperiod.Thisluminoushazehadnotbeennoticed absence ofessentiallyallauroraleffectshasbeenverymarkedhere, in appearance,anyauroralphenomenawithwhichIamfamiliar. September of1911.Atthesametimeitisalsotruethatasimilar for theydonotseemtoresembleinanyway,eitherpositionor way havebeenofauroralorigin,butthisIdonotthinkisprobable, features intheProceedingsofAmericanPhilosophicalSocietyfor May-June 1911.Itistruethatthesepeculiaritiesmightinsome any onepartofthesky.Ihavegivenanaccountthesesingular strips andmassesofself-luminoushazewhichwerenotconfinedto here onthenightofJune7,1910,andconsistedslowlymoving on, inJuneandforatleastayearafterward.Itwasfirstnoticed No. 3,p.19) other widelydistantplaces.(SeeTransvaalObservatoryCircular, a coincidence,butsomethingsimilarwasreportedonthatdateat unusual phenomenon,ifseenonlyatoneplace,mightbeconsidered conditions becameabnormal,asstatedabove.Ofcoursethis 378 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Observations ofthephysicalappearancemight havebeenvery I wouldbemoredisposedtobelievethatthisphenomenonof The mostsuggestivephenomenon,however,wasapparentlater TETE COMETWITHTHELARGETELESCOPE E. BARNARD 1914ApJ 39. . 37 3B © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Upper figures,May3;lowerfigure,4 Drawings ofNucleusandAppendages PLATE VII 1914ApJ 39. . 37 3B hm instrument. Asitwas,thecometcouldbeobservedwith the largetelescope.Itwasnecessary,however,forittohawe large telescopeonlyafterdawn,whenthenucleusanditsbrighter attained aconsiderablealtitudebeforeitcouldbeseenwiththat appendages alonecouldbeseen.Thesmallnessofthefield(5'5) very fewobservationscouldbemadeduringthemorningvisibility* and thegreatpoweroftelescopewouldhavemilitatedmuch against itssuccessfuluse.Fromthecloudedconditionofsky in AprilandMayof1910.Afewratherunsatisfactoryviews were had,mainlywhenobservingthecometforpositionlater,in however, wereobtainedonthemorningsofMay4and5,when comet waswatchedinthecomingdaylightasitfadedfromview. the lastofMayandinJune.Themostinterestingobservations^, were twowingstothenucleus,southernofwhichwas Bruce telescope,thecometw^sobservedwith40-inch.Its aspect inthelargeinstrumentwasrathersingular.Atfirstthere brighter. Thenorthernone,indeed,wassomuchfainterthatit gave thenucleusanditsappendagesaveryunsymmetricalappear- nucleus withthesouthernonealonevisible.Itthenverygreatly ance. Daylightsoonblottedoutthenorthernwing,leaving northern wing,andatió2owhenonlythesouthernwing resembled thenaked-eyeappearanceofagreatcomet,withnucleus and tail.Theaccompanyingsketchesshowthenucleuswings nucleus werevisible(uppertwosketchesofPlateVII). as seeninthe40-inchtelescopejustbeforedawnobliterated its appendagesweremoresymmetrical.WhileonMay3the matter wasnearlyallonthesouthernsideofnucleus,it evenly distributedonMay4(seelowersketchofPlateVII). interesting wasshownonJune6,1910.On thatdatealong nected streamer.Fromphotographsmade here withtheBruce receding massappearedinthetail.Thisseemed tobeadiscon- telescope, atHonolulubyMr.Ellennan,and atBeirut,Syria,by Mr. Joy,thewriterobtainedresultsshown inTableIforthe © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm On May3(astronomicaldate),aftertheexposureswith On May4ati6i5,withthe40-inchtelescopenucleusand Of thephysicalphenomenapresentedby comet,themost VISUAL OBSERVATIONSOFHALLEY’SCOMET VELOCITY OETHEPARTICLESTALL 319 1914ApJ 39. . 37 3B ings onwhichthewholecometwasvisible,were bothspoiledbythe of thetailisperhapsnotshown. stnicture, whichismoreorlesslostinthereproduction. Attention hasbeencalledinthenotestofactthatheavysmoke the comet,byaheavynorthwind. smoke fromthepower-housethatwasdriven south,directlyover judge forhimselfoftheprobabilityanychangeinactualform of theendmass. actual exposure-timebyone-half.Fromthiscausethefullwidth from thepower-housewasdriftingovercometthroughout exposure ofthisplate,andthatineffectitmusthavecutdownthe in PlateVIII.Theyareherewithpresentedsothatthereadermay nearest thecomet’sheadwasmeasured,butthisenditselfmayhave possible changeintheformofmass.Inallcasesend however, thatsomeuncertaintyexistsintheresultsowingto apparent motionlargerthantherealone. shortened bydissipationofitsmaterial,andthusproducedan of 14miles,or-22km,persecond.Itshouldhavebeenstated, mass, whichinthelasttwophotographsamountedtoanincrease motion oftheobjectandhence,also,forparticles Honolulu-Beirut of thecomet’sheadfromsunwas16.6miles(26.7km)per Y.O.-Beirut .... forming thetail(A.N.<186,11,1910).Atthistimerecession Y.O.-Honolulu . second. 38° © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem The tailofthecometonMay29(PlateXI)shows considerable It wasunfortunatethatMay4and5,theonly twogoodmorn- Plate IXisareproductionofthephotographMay4. I havecombinedthesethreephotographs(inthenegativeform) These resultsshowadecidedaccelerationinthemotionof Station Interval IO.90 iS-iS 4^25 E. BARNARD Hourly Motion 3.'60 S.78 5-17 TABLE I Miles 37-3 33-1 23.1 From Comet Recession perSecond 37-2 59-7 53-3 Km 49-7 39-7 53-9 Miles From Sim 86.4 80.O 63-9 Km © American Astronomical Society

PLATE VIII Provided bytheNASA Astrophysics DataSystem

Discarded Tail Receding erom Halley’s Comet 1914ApJ 39. . 37 3B © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm 10-inch Lens.May4,2i2G.M.T.Exposure40™ Scale: 1cm=o?4i PLATE IX 1914ApJ 39. . 37 3B unfortunate circumstancesforobservationat theYerkesObserva- morning skiesofAprilandMaycouldnothave beenundermore promise ofthesplendiddisplayitwasdestined tomakelater,inthe month ofMay.Itsreappearancefrombehind thesunin seemed asifeverythingcombined,onthisparticular occasion,to much earlierwiththatinstrument.Theincreaseinbrightness tory. Thatpartoftheyearisalwaysunpropitious here,andit was notveryrapidandaslatethelastobservationsinFebruary many inthesky.Itwasbynomeansatlimitofgreat its visibilitywasthatthestarStLeonisremainedinitorcloseto of June6(PlateXII). 40-inch telescopeoftheYerkesObservatory,onSeptember15,1909. berg, Germany,onSeptember11,1909.Thefirstvisualobserva- was toofaintforeitherinstrument.Asifinacknowledgmentof ful searchforHalley’scomet,bothphotographicallywiththe it foralongtime.Thetailseemedtobeslippingeastwardbyor Map, fortheloanofhalf-toneblockmadefrommyphotograph of fight,verymuchlikeafaintstellarnebula,whichthereareso by Dr.MaxWolf,withthe30-inchreflectingtelescopeatHeidel- photographic plate.Itwasactuallydiscovered,photographically, omy, thecometwasdestinedtobeseenfirstbysensitive wonderful progressmadeintheapplicationofthatsciencetoastron- and thechangingpositionofsun. over thestar.This,ofcourse,wasduetomotioncomet, telescope, andunderfavorableconditionscouldhavebeenseen Bruce telescope,andvisuallywiththe40-inch.Atthattimeit September 17,1909,thecometwasasmallandratherfaintspeck tions ofthecometweremadebyProfessorS.W.Burnhamwith the discoveryofphotographysinceitslastreturnin1835and 1910, beforethecometpassedbehindsun, itgaveverylittle © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem THE RETURNOFCOMETANDITSEARLYAPPEARANCEIN At myfirstobservationswiththelargetelescope,beginning During thefallandwinterof1908-1909,writermadeacare- One ratherstrikingfeatureofthetailduringlaststages Thanks areduetoMr.LeonBarritt,editoroftheEveningSky VISUAL OBSERVATIONSOFHALLEY’SCOMET381 THE LARGETELESCOPE 1914ApJ 39. . 37 3B watched untilstrongdaylightforachancetophotographorobserve hide fromusthegrowthofcometanditsapproachtoearth. Forest firesinthenorthernpartofstateproducedadensely secure resultsaslongthecometwasvisible. the comet.Similarlyeverycarewastakenineveningsto but aglimpseofthebrighthead.Thesky,oneverymorning,was would haveletusseethecomet,cutoffwithathickyellowveilall smoky skywhich,evenwhenthecloudsweremercifultousand 382 passage ofthecometbetweenusandsunonMay18wascoin- enabled towatchitinitsrecessionfromtheearthandsun.After cident withachangeintheweatherconditions,andwewerethus nearest approachtous. a longcloudyperiodtheskysuddenlyclearedatmidnight,onMay photography tookcareofthegeneralfeaturescomet,and May 18,atthemostcriticaltime,toobservephenomenonofits plate. Atthesametimeitisanoteworthyfactthatphotograph hope thattheymaybeofvalueatitsfuturereturns.Ofcourse point, forcomparisonwithitsappearanceintimespast,itmust photographs, andsupplementaltothem.Fromahistoricalstand- of acomet.Acarefuldescription,therefore,itsappearanceto the nakedeyeandwithtelescopearegivennearlyinfull have avaluebeyondthatofthephotograph. usually givesbutlittleinformationastothenaked-eyeappearance thus preservedanaccuraterecordofitsappearancetothesensitive present return,Iwassurprisedatthemeagerness oftherecords,and the eyealonemusthaveaspeciatvalue,independentofthat 17, andgaveusasplendidopportunitythatnighttheof I determinedtoprepareasfaithfulanaccount aspossibleofits in 1835toformsomeopinionashowthecomet wouldlookatthe rather extensivelyintothedetailsofnaked-eye appearanceof In lookingupthepublishedinformationconcerning itsappearance the comet.Ifeelthatthisisjustifiablefor the followingreason. © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem The transitionfromthemorningtoeveningskiesby The followingnotesdescriptiveofthecomet’sappearanceto In thedescriptionswhichfollowIhave,in some cases,gone NAKED-EYE ANDTELESCOPICOBSERVATIONS E. BARNARD 1914ApJ 39. . 37 3B returns. Ithereforemadeasaccuratearecordcouldofits appearance tothenakedeyeforbenefitofobserversatfuture appearance totheeyealone.Theseresultswereobtainedwhile from mydictationatthetime,byniece,MissMaryCalvert, guiding onthecometinphotographingit,andatothertimeswhen a fewmomentscouldbesparedtoexamineit.Thedescriptions, after thecometcameintoeveningskies,werewrittendown, modern field-glasses,whichforsuchworkaredeficientinfight,and pose, andfarbetter,becauseoftheirlargelenses,thanthemore when necessary.Theseglasseswerespeciallysuitedforthepur- observations, andwereusedtosupplementthenaked-eyeviews and thereforehavetheaccuracyofinspirationmoment. generally aretoopowerful. visual guidingtelescope,withafieldofabout20'.Whenphoto- graphing thecomet,noteswerekeptconcerningitsappearancein in theeveningsky,especiallynoticeableonoraboutMay26,was With field-glassesthenucleuswassmall,butofsensiblediameter, nucleus wasstellarandasbrightSLeonis,ofmagnitude2.7. this instrument. being ratheranintensificationofthatwiththenakedeye.The fainter hazynebulosity,whichranouttoformthetail—theview and ofabeautifulbluish-whitecolor;itwassurroundedbymuch naked-eye andfield-glass“nucleus”wasnotthetruenucleus.In that ithadanucleuswithinnucleus.Tothenakedeye nitude 8or9wasseeninadensernebulosity. Itwasverywell defined andveryyellow.Aboutthisdate, therefore, naked-eye the 5-inchguidingtelescopeasmallplanetarynucleusofmag- and telescopicobservationsofthenucleus would refertotwo entirely differentthingsofexactlyopposite colors. Thatwhich nebulosity abouttherealnucleus(seeAstronomische Nachriçhten, formed thenucleustonakedeyewassimply thesmalldenser 185,234). © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem A pairoflarge,old-fashionedfield-glasseswereavailableinthese The Brucephotographictelescopeissuppliedwitha5-inch One strikingfactthatwasnoticeablewhenthecometbright VISUAL OBSERVATIONSOFHALLEY'SCOMET,383 THE NAKED-EYEANDTELESCOPICNUCLEUS 1914ApJ 39. . 37 3B hm 0hm hm hm micrometer positions),whenthecometwasvisibleonlyin belonging totheearlierpartofobservations(containingalso been printedintheAstronomicalJournal,26,43,62,76,1909-1910, seen inthe5-inchguidingtelescope,butitdidnotlookanybrighter or 6oslowofGreenwichMeanTime. 384 E.BARNARD when itwaslost.Itisprobablethatwouldhavebeenfaintly nucleus withsomenebulosity.Thebrightestpartofthecometwas the tail.Therewasabroadstripofhazeineast,buthorizon and 27,147,1912.Thepresentnotesallrefertotheyear1910. telescope, andthosesimilarlymadeinitslaterstages,havealready had beenexaminedforanytraceofthetail,butnonecouldbeseen. visible tothenakedeyeifskyhadbeenclearanddark. There wasnotraceofthetail;skytoobrightandhazyto at leasttwomagnitudeslessthan°fmagnitude6.3. than whenlastseeninMarch.Thereappearedtobeadimhazy seemed clearforabout2altitude.Atió3othecometwaswell was lostindawnati658.Theskythattimemoreorless show it.Thecometwasvisibleintheguidingtelescopeuntil165i, hazy. ThecometwascertainlybrighteronthisdatethanApril as abrightish,ill-defined,nebulousstar,withnotraceoftail,and spicuous thanthestar.Thetailcouldbetraced for15'or20',but which itwascomparedforbrightness,thoughmorecon- starlike, almostwhite,andofthesixth,magnitude.Itwasnot eye visibility.Cloudspreventedanysuccessful photographs. from itsbrightnessinthe5-inch,itmusthave beenclosetonaked- quite asbrightthestarjB.Z).+7°Si2i(magnitude6.3)with with abrightnucleusandfineparabolicoutline tothehead,from clear spaceclosetothehorizon.Itwasbeautiful inthe5-inch, the cometwasnotvisibletonakedeye. Judging,however, 5-inch telescope.Whenataconsiderablealtitudethenucleuswas ii. Eachpreviousmorning,beforethebrightestdawn,sky © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm hm hm hm All thetimesrecordedinthispaperareCentralStandardTime, April ii,is35.Examinedtheskybutcouldseenotracesof Following isacarefulsummaryofthenotes.Therecords April 16,fromi545toi65.Thecometwasbrightinthe April 13,i65.Itwasquiteeasilyseeninthe5-inchtelescope April 19.Whenfirstseenatabouti52othe cometwasina 1914ApJ 39. . 37 3B hm hm 0 hm 0 0 hnL visible withthenakedeye,butskywastoopoorforonetohave which thetailstreamedoutoffieldview.Itwasnot nucleus wasofthesamebrightnessasstar5.Z).+7°5ioi seen it. it cameoutonaverybrightsky,andcouldbeseenwiththenaked was moreplanetaryandnotquitestarlike.Thecometcould the 5-inchtelescopeati545,butwasverydim.Atió2o not appearsobrightasDanieFscometinSeptemberof1907when it wasvisibleinthe5-inchuntili63o.Tonakedeyedid be seenwiththenakedeyeatanytime,skybeingtoopoor. in asimilarpositionwithrespecttodaylight. with field-glassesitcouldbetracedfor4or5.Thecomet eye forthefirsttime.Thenucleuswasbrightandofmagni- remained visibletothenakedeyeuntilió7,whenitwaslost,but tude 2or2.5.Thetailwasvisibleforacoupleofdegrees,but not bright.Beforemoonriseitcouldbetracedfor17or18. with thenakedeye. thin streakofclearersky.Thetailstretchedoutthefield following notesweremadebeforethecometrose,skybeing were estimatedtobeonemagnitudebrighterthan7Pegasi.Even The headandnucleuswereofaboutthesecondmagnitude, tail streamingupwardtowardtheright.Thetail,however,was (magnitude 7.0),butdidnotseemtobesointenseinitslight—it after themoonrosetailcouldbetracedfornearly15.The have cutthelightdownseriously. house waspassingoveritduringmostofthe exposure,andmust The cometwasfirstseenati44o.smoke fromthepower- examined carefully. 5-inch guidingtelescope,butthickhazepreventeditsbeingseen © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm hm April 20.Thecometroseindensehaze,andwasfirstvisible April 29.Thecometwashiddenbycloudsuntili545,when May 2,i54o.Thecometwasseenforaboutoneminuteina May 3.Thecometwasbeautifultothenakedeye,withalong VISUAL OBSERVATIONSOFHALLEY’SCOMET385 14hl7m traceoftail. 14 29Notraceoftail. 14 22Notraceoftail. 14 34Notraceoftail.Skygood. No 1914ApJ 39. . 37 3B 0 1 hm hm 0 hm 0 0 0hm 386 its end,andnotsomuchasifitsimplybecametoofainttobeseen. one-half thedistanceto6Pegasi,alengthof15,andseemed of thesecondmagnitude.Atabout15itwasonemagnitude little shorterthanonMay3.Itbecameverygraduallyfainter brighter than7Pegasi.Ati6thecometwasstillfaintlyvisible The head,however,seemedbrighterthanonMay3,andwasfully partly hidingitduringtheobservations,sothatexposuresmust smoke fromthepower-housewaspassinginfrontofcometand toward theend,whereitseemedtofadeoutasifthatwerereally with thenakedeye.Itwasveryfaintlyvisiblein5-inch have beencutdownineffectatleastone-half. telescope. to thenakedeye,butoneminutelaterithaddisappeared.The faintly betweenthecloudswithnakedeyeati453. covered it.Atfirstthetailcouldbetraced,eveninhazysky, brighter thanatpreviousobservations.Itcouldstillbeseen seen withthenakedeyewhenitrose,buthazycloudsatonce for adistanceof17or18.Thewholecometmusthavebeen pretty brightwithalongtail.Theviewswerefragmentarythrough eye severaltimesbetweentheclouds.Afteri5ioitseemed covered withheavyclouds.Thecometwasseenthenaked very faintlywiththenakedeye.Itmusthavebeenbrightto the breaksinclouds. it wasstillfaintlyvisiblewiththenakedeye. be seenatallundertheconditions.Thetailcouldtracedfor would perhapshavebeenseenabovethesmoke bank. passed about2or3totherightofandbelow thatstar.Itmust smoke allaroundthehorizon.Iftailhad beenverylongit could betracedslightlybeyond6Pegasi,adistance ofabout53,and 15. Theheadwasatleastofthesecondmagnitude.Atis48 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm hm May 4.Thecometwasbeautiful.tailstretchedabout May 5.Dense,thicksky.Notraceofthecometcouldbeseen May 6.Theskywasverythick.cometfairlywell May 8.Theskywasverythickandconstantlybeing May 9.Theskywasverythick.Ati55thecometseen May 13.Notraceofthecometbecause densehazeand May 14.Theskywasverythickandbad. At i44°thetail E. BARNARD 1914ApJ 39. . 37 3B 0 hm hm o 0,hm hm hm 0 hm h nl h m 0 hm many timeslessbrightthanVenus.Theobservationsalsoshow yellow andstarlike,withsomecoma,wasquitenoticeableinthe have been3or4broadnearthesouthsideofsquarePegasus. haze. Wherethetailcouldbeseenitwasverystraightandbroad. could notbetracedanywherenearthehead,whichwasinvisiblein It wasfairlynoticeablewhenlookedatwithavertedvision,but midnight. Asobservationsatthistimeareoftheutmostimpor- eye, butwasverydullandred.Ati6othenucleus,which could beseenwiththenakedeyeatanytime,becauseofsmoky the haze. earth, thenoteswillbegivennearlyinfull. very clear,butthemoonwasstillabovehorizon.Ati325 that thetailmusthavebeenabout50inlength. about 4or5high.Ati3iothisseemedeithertohaverisen At i3450Pegasiwasintheaxisoftail.5f rather rapidlyortohavebecomemorepronounced.Theskywas at i35.“Thereisadiffuseddawneffectneartheeasthorizon seemed toextendalongtheeasternhorizon.Thiswasmoremarked tance inconnectionwiththenearestapproachofcometto 5-inch telescope,butneithertheheadnoranyoftailnearit near 6andapparentlyrosetoapointio^southeastofAltair. Pegasus, andreachingnearlytoAltair.Ati335theaxisof Way. Itseemedsomewhatbrighterinthe middleandfaded 0 Aquilaeexactlyonitsnorthedge.Ati42o thetailbetweenf inside thesouthedgeandslightlyintail, while 7Pegasiwasin was onthenorthedgeoftail.Ati4i5 0Pegasiwasclose Venus, atthesamealtitude,wasfairlywellseenwithnaked tail wouldpassthrough6Pegasi.Itwasperhaps5or6°broad traces ofthetailwerecertainlyvisiblealittlesouthsquare this “dawn”effectwasashighePegasi.Ati33odistinct and 7Pegasiwasperhapsbrighterthanany portion oftheMilky slightly towardtheedges.ItjoinedMilky Wayandcouldbe the tailandperhapsone-halfdegreenorthof its middleoraxisand © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm hm At i540thecometwasfaintin5-inchtelescope,while From theforegoingobservationsheadmusthavebeen May 17.Afterastormyperiodtheskyclearedbrilliantlyat i3o. Anarrowtwilight(whichlaterprovedtobethetail) VISUAL OBSERVATIONSOFHALLEY’SCOMET387 1914ApJ 39. . 37 3B 0hm hm hm hm a hm hm hm o h m hm Pegasi (5).Ati425thetail,beyondePegasi,wasaboutone- 40-inch. Shesaysthatati5i8shecouldnolongerseethetail, width ofthetailwasalittlegreaterthandistancefromßto77 S»» Pegasi, andcouldbetracedasfarePegasi.Theskywasvery fourth asbrightorlessthanthatpartbetweenfandyPegasi. about i34oitwasthoughttobeslightlyconvexthenorth.The present. Ati44SEquuleiwasjustfreeofthenorthedge nearly uniforminlightwithrespecttoitswidth,butittapered flat anddidnotdiffusemuchatitsedges.Indeeditseemedtobe averted vision.Ati5i2itwasstillfeeblyvisiblenearfandy phenomena developedwhicharebelievedto havebeenauroral. in theair.Thiswasnoticedonlywhen,on hidingthe-moon,a along thesoutheasthorizon,asifanotherportionoftailwere looked forbutnonewasseen.Theedgesofthetailweresmooth fourths aswideatapointnearfPegasi.Thisofcoursewasan very muchtowardtheend,nearwhichitwouldnotbeoverthree- axis. MissCalvertwatcheditalittlelongerwhileIwenttothe clear. AtthistimeyPegasiseemedtobestillalittlenorthofthe tail. Ati447aEquuleiwasjustfreeofthenorthedge. The star71Aquilae(5.Ö.—i°4oi6)wasinthemiddleoraxisof traced beyond6Aquilae.Atthistimeitappearedstraight,butat below andabovethetail,thereappearedtobeabrightening and uniform.Atabouti3i5or3oIcouldseetheskydark, effect ofperspective.Streamersorirregularitieswerecarefully though shehadseenitoneortwominutesearlier. in theafternoon.Abeautifulnightwithathree-fourths fullmoon. least 107longonthisdate. sky nearthehorizon.Theobservationsshowthattailwasat either withthe5-inchor40-inchtelescope,becauseofthick feeble illuminationwasseennearit.At837 andlater,certain Every preparationhadbeenmadetophotograph anyphenomena the tail.Theheadofcometcouldnotbeseenwhenitrose, The notesonthesehavebeencollectedandare givenlater.Atthis that mightdevelopduringthenight.Therewas aslightmistiness i5io thetailwasfaintfromdawnandcouldbeseenonlyby © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem The tailwasonlyalittlebrightertowardtheaxis—itvery May 18.Beautifullyclearallday,withafewflecksofclouds E. BARNARD 1914ApJ 39. . 37 3B © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Drawings orTailsofHalley’s Comet h May 18,G.M.T.2i PLATE X 1914ApJ 39. . 37 3B hm hm hm hm hm 1m hm hm misty lookeverywhere,whichwasnotduetoordinaryhaze,for faint mistinesswhichhadbeenvisiblesincedark.Atio4othe wasvisibleunderCassiopeia.Theskyhadafeeble moonlit. Ati42othetailwassurelyvisible intheeast.Itwas eastern horizonwasbrightwithadiffusedluminositywhilethe apparently theskywasveryclear.Uptoio35nothingoutof able twilighteffectinthelownorthwest.At856somefaint be alittlenorthofitspositiontheprevious morning(a.m.of was verybright.(Thislaterprovedtobethe comet’stail.)At At i242theeasternhorizonforperhapsone-fourth thewayup time theskyappearedunusuallygood.Therewasstillaconsidér- the ordinarywasnoticedinappearanceofsky,except western horizonwasfreefromanythingofthiskind.Ati2ío May 18).Ati423yPegasiwasjustinside the southedgeof quite noticeableatthistime,eveninthemoonlight. Itseemedio the illuminationofeasternhorizonseemedtobealittlebrighter.- i4io thetailwascertainlyvisiblejusteast of 6Pegasi.Skystill © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Key-map fordrawingsofthetailHalley’sComet,onMay17and18 VISUAL OBSERVATIONSOFHALLEY’SCOMET,389 1914ApJ 39. . 37 3B o 0 h hm hm hm hm hm part ofthetailcouldbesaidtoroughly cone shaped,withits globe, makethelengthoftailatleast120 . entirely duetodawn.Theobservations,located ona.celestial base alongthehorizon,andtaperingoutbecoming fainttoward forms theGegenschein,orlikelightreflectedfromdustparticles; unsteady. Theilluminationbelowthedarkspaceintail, 7 Pegasiwas3insideofthesouthedgetail.Thenorth sky seemedtoassumeafeebleglowthatdid notappeartobe Andromedae. Thelightofthetailwasverysimilartothatwhich southeast horizonasifitpassedbelowthehorizon,andthereseems brightest partofthetailfluctuatedinbrightnessasifitslightwere 0 Aquilae.Asdawnapproached,sayalittle afteri5,thewhole that is,itdidnothaveanebulousappearance.Thebrightnorthern was noevidenceofanystreamernorththebrighttail.The no questionthatitwasaseparatepartofthetail,and At i5iothetailanddarkspacewerestillfeeblyseen,butthey between dand€Pegasi,nearerto0.Itwasstronglyvisible(moon 390 side wasverydiffused.Attimesitseemedtodiffusebeyonda dark spacewasariftthatseparatedthetailintotwoparts.There gradually andreachedhalfwayfrom7PegasitoaAndromedae. nearly down).Ati427thenorthedgeoftaildiffusedvery south edgewasratherdefinite,thoughsoftlyblended,butthenorth though feeble,Ithinkwasreal.Itapparentlyextendedtothe Milky Waybeyond0Aquilae,whereitbecamefaintandsomewhat bright asonthepreviousmorning.Thetailcouldbetracedto were badlydimmedbydawn. horizon, wideningouttowardtheeasthorizon.Ati54tail wide nearthatstar.Ati452thetailcouldbetracedto diffused three-fourthsofthewaytoaAndromedae,andwasio° Both 0AquilaeandfPegasiwereintheaxisoftail.Ati442 bright astheMilkyWay,butdidnotseemtobemorethanhalf could stillbeseen(thoughitwasdim)andthedarkregioninit. tail, whileaPegasiwasjustinsideitonthenorthedge.Itlay tapered. ItcouldnotbetracedacrosstheMilkyWay.Several timés theimpressionwasgiven—Ialmostsureofit—that © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem On bothnights(May17and18)therewasnodecided fightnorth The brightestportionofthetailnearaand7Pegasiwasas E. BARNARD 1914ApJ 39. . 37 3B hm hm hm hm hm hm 0 hm hm hm hm hm hm hm hm hm hm hm hm glow. Atii24thereseemedtobenoaurora. Atn32,no faded out—apparentlydead.Atnioa veryslightauroral extended halfwaytoCassiopeia.Byio40the aurorahadalmost siopeia. Atio32stilldiffused,withnodefinite arch,andone feeble arch.AtI4i4thealtitudeofarch was3or4. aurora. Ati352theaurorastartedupagain withaverylow streamer movingwest.Thebrightestpart oftheillumination general illuminationwaspresentreachingnearlyashighCas- left. Atioi6thearchwasratherstrongbutindefinite. way fromthehorizontoaCassiopeiae.Atioi2streamerswere bright partofthearch(whichwasfairlystrong)exactlyhalf- it hadbecomeauniformglowextendingalmostashighCas- visible underCassiopeia.At92apparentlyaslightaurorawas streamers. Atio28therewasnodefinitearch,butadiffused ascending totheleftofsummitarchandmoving siopeia. Therewerefeebleattemptsatactivity94oconsisting luminous bandwasvisiblehalfwayfromthehorizontostarsof minutes later.Atthistimeconsiderabletwilighteffectstill parison withobservationsthatweredoubtlessmadeelsewhereand of agreatnumbershortstreamers.Atio4thealtitude visible totherightofandbelowCassiopeia.At9i4afaint remained inthenorthwest.At856somefeebleluminositywas light inthenorthaboveCassiopeia.Theyhaddisappearedfive Cassiopeia. Thisseemedtobeanauroraleffect.At92o for otherreasons.Ihavethereforecollectedallthephenomenathat best togiveithereasapartoftherecordforthatnightcom- active aurorawithstreamersflashedupverysuddenly.By928 below thebrighterpartoftailwasdecided.Itsoftand mistiness mentionedintheprecedingparagraph.Theillumination certainly seemedtobelongtheaurorainnotesthatfollow. seemed toreachandbeyondthesoutheasthorizon. and freefromunusualillumination,withtheexceptionofslight of thetail,thatis,allskyabovetailwasapparentlypure tainly hadnothingtodowiththeproximityofcomet,itseems ioi8 theaurorawasagainactive(butnotbright),withdiffused © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm At 837thereseemedtobesomehorizontalstreaksofdiffused Although theslightaurorawhichdevelopedonMay18cer- VISUAL OBSERVATIONSOFBALLETSCOMET 391 392 E. E. BARNARD

There are no other notes on the aurora, and I assume that it finally disappeared about this time. Notes were also made of the appearance of any meteors, but they are not given here because but very few were seen on May 18 and none was noted on May 17. They seemed to have no connec- tion with the comet. May 19. Cloudy at night. No observations of the comet possible. May 20. At 7h5om to 8h30m with the naked eye the head was one-half degree in diameter. The head and nucleus were of about the second magnitude, and resembled a yellow nebulous . There seemed to be a faint diffused tail. The sky was muggy, and the comet was in clouds most of the time. In the 5-inch the nucleus at first was very stellar and very yellow, with some of the hazy yellow light about it, but no tail was seen with certainty. The sky was examined repeatedly as late as iih, but no trace of the comet’s tail was anywhere visible. The moon was nearly full. At i4h the sky was hazy in the west. At about i4h30m a hazy luminous streak 40-5° broad extended from 6 Aquilae to the east —fainter toward d Aquilae—through a Pegasi. This resembled the comet’s tail, but was doubtless a strip of haze. I looked at it several times, taking it for a strip of haze, but it did not seem to move. There were masses of moving haze overhead toward the north. To all appearances it looked like the comet’s tail of the mornings of May 18 and 19. I cannot be certain that this was not haze, but it was a singular coincidence of position, appearance, etc., if it was. It was visible for fully 15 or 20 minutes. Then the sky got worse with the haze and moonlight and it disappeared. At the same time there seemed to be a similar strip in the low south which stretched from the Milk Dipper in Sagittarius to Antares. This was 30 to 40 wide. I think these must have been merely strips of haze, and had nothing to do with the comet, but they are given here as a matter of record. It may be well to note, however, in this connection that the tail—both branches—-was still visible in the h m morning sky in South Africa on this date, at i5 30 G:M.T., Or

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1914ApJ 39. . 37 3B 0 0 hm0 hm hm 0hm hm hm only fivehoursearlierthanthesupposedobservationrecorded were alsoseenbyPerrineatCordobaonthe20thsame minutes throughabreakintheclouds.Itwasverybright—^per- above (seeCircularsjandu,TransvaalObservatory).Bothtails moon andhaze,patchesofwhichfrequentlycoveredthecomet. haps brighterthanthefirstmagnitude.Tonakedeye moment asmyobservation(seeAstronomicalJournal,26,145). nucleus andcomaappearedlikeanebulousstar.Therewassome faint tail.Duringtheexposuresskywaswhitewithafull with tracesofthetail.Itwasbluishwhiteandastrikingobject. was 25long.For5°or6°itnoticeableandthenbecame The headwaslargeandhazyabout15'or20'indiameter. late toaidintheobservationsofcomet. The totaleclipseofthemoononthatnightunfortunatelycametoo At io°fromtheheadtailwasabout2wide.Thefightof The nucleusresembledafirst-magnitudestarinhaze.tail noticeable tothenakedeye.Tenminuteslatertailwasvery rapidly fainter.At83Sitwasquitenoticeableforio°or15. moonlight anddidnotseemtobeveryclear,butthetailwasstill with thenakedeyefor29.At9ioskywasverybright comet wasstillbluishwhite.At85othetailcouldbetraced At io3othecometwasstillvisible,,verylowanddim. feeble forwantofcontrastandatiooitwasscarcelyvisibleto observations ofProfessorA.E.DouglasatTucson, Arizona,who greater indiameterthanwhentheexposure began,andmoreill point, butmorelikeasmallbrightplanetwithcoma.At845 defined—it seemedtoswellinsize. it wasnearlywhite.Italsoappearedwhitetothenakedeye. the nakedeye,butheadwasstillverybrightlikeahazystar. Observatory Bulletin,No.412.] In thelastpartofexposurenucleus was aboutfivetimes later, onthissamedate,sawthenucleusdouble. SeeHarvard © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm hm May 21and22.Cloudy. May 23,S4o.Skycloudy,butthecometshoneforafew May 24.At75thecometwasquitebrighttonakedeye, In the5-inchtelescopenucleuswassharplydefined,nota [The lastpartoftheforegoingparagraphisin accordwiththe VISUAL OBSERVATIONSOFHALLEY’SCOMET 393 394 E. E. BARNARD

May 25. At S^o111 the tail could be traced for 210. The head was decidedly less intense than e Hydrae south of it. The sky was quite good. At 8h5om the tail could be traced for eight-tenths the distance between the head &n.à' Jupiter, or a length of 430. At 8h55m the comet was seen on a fairly dark sky, only a little twilight effect remaining. It was very beautiful, though the head did not seem relatively so bright as on other nights. The tail, for about 200, was pretty bright, and increased very much in width. At 9hom it seemed to extend in a very diffused manner nearly to the same as that of Jupiter, a distance of 540. Prolonged, its axis would pass about 8° south of Jupiter. The tail was very diffused at its end and seemed to extend northward nearly to Jupiter. At 9hiom the central brightness of the head was almost bluish white in the field-glasses. At 9h3om the sky had begun to whiten with moonlight, but the comet was still in good relief, the moon being behind clouds in the east. At 9h35m the tail could be faintly traced several degrees beyond 87 Leonis =

B.D. — 2°?>i)6o (magnitude 5.0), which at this time was in the axis of the tail, or for about 430. At 9h55m the tail was very dim on the bright moonlit sky, but was still faintly visible for io° or more. At 8h3om with the 5-inch telescope the nucleus was very small, like a ninth- or tenth-magnitude star. The coma was very large and fairly bright. Before the wires were illuminated the nucleus did not appear double, nor were there any other nebulosities in the field of view. It was very dim and hazy. At 8h5om the nucleus was of. the same brightness as 7° 20$$ (magnitude 8.4). At 9hi5m the nucleus was a little brighter and hazy. At 9h35m it was fairly stellar and a little brighter—-brighter than any of the in the field of view: (B.Z>.+7°2048 [magnitude 9.0], +702052 [magnitude 9.2], +702o55 [magnitude 8.4]). At 9h5om the coma was very dense and extended perhaps 5' all around the nucleus, which was very small and dim. May 26, 7h55m. The comet was visible to the naked eye as a faint hazy star. At 8h5m it was quite noticeable, with perhaps faint traces of tail. At 8h22ni the tail was showing faintly to the naked eye. The comet seemed less bright than on the previous night. At 8h3om, with field-glasses, there seemed to be a central

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1914ApJ 39. . 37 3B 0hm hm hm hm hm 0hm hm hm hm0 0 hm o nucleus, fairlywelldefined,large,andbluishwhite,surroundedby in thetelescope.Thetailwasvisibleforio°or15.At84othé much fainterhazynebulositywhichextendedfromittoformthe magnitude. At84Stheskywasverygoodandtail ever, wasnotthetruenucleus,whichverysmallandseenonly noticeable. Itcouldreadilybetracedto87Leonis.Withfield- tail wasverynoticeableforabout15°,butitfadedrapidly glasses thenucleuswasanintensebluishwhite.Thewholehead faint. Itseemedalittlebrighterinthemiddlenearhead.No toward theend.Toeyenucleuswasbright—-ofsecond tail. Ithadthesameappearancetonakedeye.This,how- spicuous halfwayto87Leonis,afterwhichitbecamediffusedand seemed tobeofabluish-whitecolor.At85othetailwascon- very muchbrighterthantherestofhead.At9otail be tracedfeeblyio°beyondit.Tothenakedeyenucleuswas very muchinferiortôRegulus.At85thetailwasconspicuous conspicuous andstrikinglybeautifulobject.Butthenucleuswas streamers wereseen.Theskywasfairlydarkandthecomet4 as far87Leonis,and,thoughratherfaintnearthatstar,itcould ing objecttothe*nakedeye,withthetail,whichseemedbe bright ashLeonis(magnitude2.6).Thecometwasaverystrik- could beveryfeeblytracedbeyondJupiter.Theaxiswouldpass 6° or7southoftheplanet.At9ionucleuswasaboutas half amagnitudelessbrightthanyLeonisof2.6.At 9i5, byhidingJupiter,thetailcouldbefeeblytracedtoa straight, reachingasfar87Leonis,whereitbecamefaint.At it was4or5timesasbrightPraesepe.At945thecomet 92o theskywasstillgood.Thetailfor15fromhead glasses thetailwidenedoutverymuch.The nucleuswaslarge everywhere brighterthanPraesepe.Within5orio°ofthehead glow ofthesamecolor.Thereseemedtobe nostructureinthe seen onafinedarkskyandwasveryconspicuous. Inthefield- tail. At95othemoonwaswhitening easternsky,butthe and bluishwhitewassurroundedforashort distancebyahazy It graduallywidenedout,withthesouthside perhapsalittlethe tail wasstillnoticeableasfar87Leonis,where itbecamefaint. Virginis, oralengthofabout65.Thenucleuswasperhapsone- © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem VISUAL OBSERVATIONSOFHALLEY'SCOMET 395 1914ApJ 39. . 37 3B hm hm0 hm hm 0 hm hm hm hm hm hm hm hm illumination. At838thetailcouldbeseen ratherdimlyfor 835 itwasonlyfeeblyvisibleforperhaps5 or6°,butitcouldbe stated thatitmusthavebrightenedsincetheexposurebegan.It ^96 brightness butwasveryilldefined.Atio$itdecidedly very muchbrighterthanonMay25.Thenucleuswasestimated about io°—skystillluminous.Inthefield-glasses thecondensation seen fairlydistinctly.Theskywasverypoor withsometwilight or. nucleuswasofabluish-whitecolor.The rest oftheheadand time. At825thetailcouldbefeeblyseen for4or5.At smoky, andhadbeensoalmostallthelateafternoon.At8i5 very faint. its lightwasnotsointense.Itveryhazyandmuchlarger more yellowandperhapsalittlebrighterthanthesamestar,though was illdefinedandperhaps5"=*=indiameter.At935thenucleus was verymuchbrighter.Itseemedtohaveincreasedgreatlyin planetary, andwiththecomawasveryyellow.Thenucleus brighter. Tothenakedeyenucleuswasratherdull.In dim cloud,inwhichthenucleuswassmallandfaint.Thesky it wasbrighter,andmoreyellowthanthestar.Itseemedtobe larger andperhapsslightlybrighterthan6°212g(magni- the cometwasdulltonakedeye,likeanebulasomeio'or than thestar.Atio5ocometandnucleuswereboth to bedecidedlybrighterthanthestarat95,andioitwas naked eye. At io20theskywasverybrightwithmoonlight,butcomet’s could stillbetracedfeeblyforio°ormorefromthehead.At could betracedfaintlyasfar87Leonis.Atio3othetail field-glasses itwasstillbluishwhiteandhazy,likeastarshining tude 8.0),whichwasinthefield.At84o,thoughlessintense, some treetops,andnothingcouldbeseenofthetailwith dence ofstreamers,eitherwiththenakedeyeorfield-glasses. through abluish-whitemist.Theredidnotseemtobeanyevi- tail wasstillnoticeable(thoughnotverystrong)forsomeio°,and 15' indiameter.Onecouldnotbesureofseeing anytailatthis io5o thecometwasverynearhorizonanddisappearingin © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm hm At 75,withthe5-inchtelescopenucleuswassmalland May 27,8o.Tothenakedeyecometresembledasmall E. BARNARD 1914ApJ 39. . 37 3B hm hm hm hm hm hm hm 0 0 hm hm 0 hm hm hm able andcouldbetracedreadilytoLeonis. At io4othehead near thehorizon,butwasstillstronglyconspicuous. Byio3o pure. Atio2othecomet’sheadwasgetting downintothehaze the headwasbecomingdimtoeye.The tailwasstillnotice- of thethirdmagnitude.Theskywasfair, though notspecially 945 thecometwasstillaconspicuousobject, withthetail extending to87Leonis.>Thenucleusresembled adullhazystar little southofthemiddletail.Thenucleuswasinpretty planet (ai2iç,S—o^i').ThestarLeoniswasperhapsa part ofthetailnearJupiter,extendingtonorthashigh nucleus wasofsensiblediameterandhazyverystrongly Jupiter itcouldbetracedtoapointhalfwaybetweenand faint. At93o,withthefield-glasses,whatappearedtobe 87 Leonistotheend,becameexceedinglyfaintanddiffused.At strong contrasttothetailnearhead.At940tail,from curved whenthewholetailwasconsidered,withconvexside toward thesouth.NearJupiteritwasperhaps3inwidthand a Virginis,orfordistanceof5354.Itseemedcertainlytobe spicuous object.Thetailneartheheadwasverymuchbrighter was fair.Possiblythetailslightlycurved,withconvex With thefield-glassestailnearheadwasfeeblybrighterin it wasconspicuous.Theskyfairlydarkbutnotpure. than Praesepe,butitfadedoffrapidlynear87Leonis.Byhiding side south.Itwasquite,noticeableasfar87Leonis.At brightness between7(magnitude2.6)andfLeonis the middle.At9ioconditionofsky,thoughnotpure, brighter onthesouthsideandcouldbetracedquitedistinctlyto noticeable. ThecometdidnotseemasbrightonMay26,but conspicuous. At935thereseemedtobeadiffusionfromthat 87 Leonis(whichstarwasapparentlyintheaxis,orperhapsalittle south ofit),afterwhichjtbecamefaint.Forone-halfthatdistance the skywaspoorandwhitish.Thenucleusaboutmidwayin Leonis (about33),andneartheheadfor6°or8°itwasquite with thefield-glasses.Tonakedeyecometwasacon- 9i5 theredidnotseemtobeanystructureinthetailasseen 5.1), oraboutmagnitude3.8.At9othetailseemedtobe tail werewhitish.At842thecouldbetracedfaintlyto87 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem VISUAL OBSERVATIONSOFHALLEY’SCOMET 397 1914ApJ 39. . 37 3B 0 hm 0 hmwas 110 hm hm hm hm / hm J0h hm near théhorizontherewasagooddealofsmokyhaze. nucleus wasaboutasbright77or0Leonis. Thetailseemedto Jupiter andSpica,orabout52,butonlyfeebly. Itwasnoticeably very smallandfaintwasapparentlyonlyacondensationin not havebeenthetruenucleus,forin5-inchnucleuswas was verydim.The"tailalsodim,butcouldstillbetraced diffuse tothenorthJupiter,andperhapsbeyond. Thesouthern visible toguideon.Idonotthinkitsfaintnesswasdueentirely have beenwhatappearedtothenakedeyeasnucleus.At dim, andwasveryfeeblycontrastedwiththenebulosity.At 8.1, whichwasinthefieldwithit.At845nucleusvery to 87Leonis,wasalittlethebrighterand more definite.The a distanceof27,itsaxispassingaboutone-half degreenorthof cernible, beingallbutlostinthecoma.Atio35^longer very strongandtherewasnocontrast.Itsimplyacentral dense nebulosityi'ormoreindiameter.Thismust 95o thetruenucleuswasverysmallanddim,several 85o whatwassoconspicuousasanucleustothenakedeyecould to 87Leonis.Theskyuphighandoverheadwasveryclear,but 398 defined, withsomehazeaboutit.Itwasverymuchfainter curved—convex tothesouth.Thesouthern side,fromthehead that star.Itcouldbefeeblytracedbeyond thelinebetween the conditionofsky. condensation ofthecoma.'Atioisnucleuswasjustdis- times fainterthanthestarjB.Z).+5°2i7i.Itwassurroundedbya and showedaboutthesameamountofcontrast,brightpart appeared verymuchlikethenucleusandclosenebulosityof and wasverysmallilldefined.At935thenucleuscoma seemed tohavegrowndimmer.Itwasratherdifficultguideon the coma.Itmust,therefore,havebeenbrighterpartof the comabeingabouti-2indiameterandverydiffused.At coma whichformedanucleustothenakedeye.At9ioit Great NebulaofAndromedawhenseeninanordinarytelescope, (perhaps twomagnitudes)thanthestarB.D.r$2i]iofmagnitude io5 thenucleuswasdifficulttoguideon.Theglowaboutit © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm hm At 85thenucleus,in5-inchtelescope,wasfaintandill May 29.Atio5thetailwasconspicuousasfar87Leonis, E. BARNARD 1914ApJ 39. . 37 3B © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hmb 10-inch Lens.May29,i539,G.M.T.Exposure,i57 Scale: 1cm=o?55

PLATE XI

North 1914ApJ 39. . 37 3B 0 hm hm hm 0 hm 0 hm 0 hm hm noticeable asthestarttLeonis.Therewasnotailvisibleatthis in theaxisoftail).Forabout15itwasconspicuous.The nucleus. Therewasperhapsafaintsuggestionoftailforcouple Leonis (magnitude4.9),perhapsalittlebrighter,butmorenotice- bright andseemedtobeanebulousmasswithoutanyspecial time. Theskywasveryclear.At83owiththefield-glasses eye likeafaintnebula.At82oitwasnotasbrightnor With thefield-glassescondensationinheadlookedlike resembled abrighthazynebulosity.At9i5thetailseemed head wasofaboutthethirdmagnitude,andwithfield-glasses seen faintly7or8°beyondthatstar(whichseemedtobenearly of degrees,butveryfaint.Theheadwasaboutasbrighttt tail couldbetracedforacoupleofdegrees.Theheadwasquite previously noted,butJupiterwastoobright to makethiscertain. decidedly curvedbetweentheheadand87Leonis,withconvex sky wasstillbrightwithtwilight.At85othecometquite 87 Leonis,adistanceof25,butwasfainttowarditsend.The able thanthatstar.At84othetailcouldbetracedasfar The measureddiameternorthandsouthfromonesettingwas edge wouldaboutbisectthelinebetweenSpicaandJupiter.The comet wasdecidedlylessbrightthanonMay27. same appearanceofdiffusingandspreadingout towardthatplanet compared withitsappearanceafewnightsearlier, butitwasstill fainter nebulositywhichextendedbacktoformthetail.The conspicuous. Thetailwasnoticeableasfar87Leonisand as far87Leonis,afterwhichitbecame faint, butbyhiding The skywasverytransparent,especiallyin highaltitudes.At same brightnessasPraesepe.Nearertheheaditwasbrighter. side tothesouth.Atabout5fromheaditwasof 940 thecometwasastrikingobject.The tail wasconspicuous conspicuous. Thetail,whereitpassedbelow Jupiter,hadthe head. At925thecomet,tonakedeye,wasverydullas central brightnesswasverystrongascomparedwiththerestof a largediffusednucleus,bluishwhiteincolor,surroundedby 2?6. © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm In the40-inchnucleuswasnotyellow,butpaleincolor. May 30.At85thecometcouldbefeeblyseenwithnaked VISUAL OBSERVATIONSOFHALLEY’SCOMET 399 1914ApJ 39. . 37 3B hm 0 hm hm hm hm hm hm hin hm hm 0 Jupiter itcouldbefeeblytracedasfarthelinebetween 4OO irregularities couldbeseeninthetail,whichdiffusedverysoftly part someio°backfromthehead,asiftailsaggedalittlesouth was lostinclouds. the comet,thoughlow,wasstillconspicuous.Theskyseemedto glasses. Atthistimeitwasstillaconspicuousobject.io30, and Spica,alengthof47.Withthefield-glassesnostructuresor nucleus wasverysmallandstarlikeshoneinthemiddleofa be verygoodinitsdirection.Theheadwasquitebright,andthe No streamerswerevisibleeitherwiththenakedeyeorfield- toward theedgesandwasnotespeciallybrighterinmiddle. very smallandfaintinthe5-inchguidingtelescope.At835 at thatpoint. quite bright,likeasecond-orthird-magnitudestar,butthetail tail couldbereadilytracedto87Leonis.Atio45theheadwas nucleus, northandsouth,was4^9. was conspicuous. densation aboutit. 3°2273. Atioi7thenucleuswasalmostlostinstrongcon- haze closeaboutit.Itwasnotverymuchbrighterthan clear. At945thenucleuswasverysmallandstellarwithsome B.D.+3°2273—-about magnitudesbrighter.Theskywasvery which diffusedgraduallyfori'=*=.Itwasverymuchbrighterthan brighter thanthestar3^273ofmagnitude9.2.At9io dense nebulosityabouto'5indiameter.Itwasonemagnitude 8i7. Theskywascoveredmoreorlesswithhazyclouds,butat 9o, inspiteoftheconditionsky,tail couldbetracedto eye. At840onlyfainttracesofthetailcould beseen.Thesky about io45,whenseenforafewminutesbelowtheclouds,it the nucleuswasverysmallandstarlikeinadensenebulosity at thistimewascoveredwithhazycloudsfrom thenorthwest.At 87 Leonis,adistanceof22.Thecometwas coveredwithhazy j © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm hm hm At 85,thoughtheheadwasdistincttonakedeye,it During theexposuresoncometthereseemedtobeadenser June i.At8iothecometwasfaintlyvisible tothenaked In the40-inchtelescopeat842measured diameterofthe May 31.Thecometwasfirstseenwiththenakedeyeat E. BARNARD 1914ApJ 39. . 37 3B x wasperhaps3'or4'indiameter.Theminute nucleuswasabout h 0 hm hm 0 J 0 hm hm moving southwardly,whichwere,mostofthetime,onlyafew have beenseenonagoodskythroughouttheobservations.Oncein noticeable asfarthatstar.,Thehead,whichseemedbrighteron good inthedirectionofcomet.Thetailcouldbetracedfor clouds nearlyallthetime.Therewerelongstripsofthese rest oftheskywasgood.Afterioitgotontoabetterand a whileitcameoutforfewminutesonlytobecoveredagain.The degrees wide,andiftheyhadbeendisplaced4or5thecometwould —-just visible—inastrongcondensation.At85itcouldno there wasverylittleinterferencefromclouds,buttheskynot Leonis fairlywell,andcouldbetracedsomedegreesfarther.Its tail, inmomentsoffreedomfromclouds,couldbeseenupto87 or 3^1.Atno,thoughthecometwasverylowanddim, this date,wasaboutmidwayinbrightnessbetweenyandrjLeonis, several degreesbeyond87Leonis,orperhapsforabout25,andwas which seemedtobestraight,couldquitereadilytraced87 magnitude brighterthanthestar15Sextantis=B.D.ro°26-L$ longer beseentoguideon. axis passedslightlynorthofthatstar. Leonis andperhapsafewdegreesbeyond,butitwasdim.It visible inadiffusedmannertothestar%Virginis,orabout33. placed inaverystrongnebulositywhichfaded awayrapidly,and At 9oitwasaverysmallpointindensehazy lightwhichwas To thenakedeyeafaintnucleuswasdoubtfullyvisible.Thehead With the40-inchtelescopeitselfat82o,nucleuswasvery was aboutasbright87Leonis,andnotmuchmorenoticeable brightness oftheheadwouldbeabout2Jmagnitudes lessthan three magnitudeslessthanthecomparisonstar (estimatedmagni- small, 2"or3"indiameter,andsurroundedbyadensenebulosity. tude 9=1=;seeAstronomicalJournal,27,149,1912), butthegeneral than thatstar. the star. (magnitude 4.1)andmoreconspicuousthanthatstar.Thetail, © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm hm hm June 5,97.Tothenakedeyeheadwasaboutone-half At 8iointhe5-inchnucleuswasveryfaintandsmall The cometwasfirstseeninthefinderof40-inchat89. VISUAL OBSERVATIONSOFHALLEY'SCOMET 401 1914ApJ 39. . 37 3B 0 hm hm 0hm 0hm hm hm 0 hm 0 0 4O2 At bestthetailcouldbeveryfaintlytraced to87Leonis,or E.D.+o264i, orabouttheninthmagnitude. a brightstarlikenucléus,whichwasaboutone-halfmagnitudeless its formerself. June i,andthoughanoticeableobject,wasonlytheghostof was onitsupper(north)edge,andcouldbeseenfeeblyseveral Leonis (whichstarwasinthenorthedgeoftail),adistance bright thanthestarE.Z).+o°264i(magnitude8.0).At835 degrees beyond.Skygood.At957thetailcouldbetraced of 18.At9ioitwasnoticeableasfar87Leonis,which of 5.At87itcouldbeseenfaintlyto87Leonis,adistance tude 3.8).At85othetailcouldbetracedforadistance The headwasnotquiteasnoticeablethestarpLeonis(magni- eye asafainthazyspot.At847thetailwasnotyetvisible. a strongcondensationwhichwasratherhardtoguideon. with mistyclouds. everywhere elsebutintheregionofcomet, whichwascovered for 15.Inthelatterpartofobservations theskywasgood clouds. Thecometwasonlyfairlyvisible tothenakedeye. In the40-inchtelescopeitselfnucleus,whichwasinavery clouds, however. The skywaspoorandtheMilkyWaydull.Therewereno fainter withrespecttothetailthanatpreviousobservations. of aboutthesamebrightnessasstarpLeonis.Itwasrelatively best seenat942thenucleuswasaboutonemagnitudelessthan condensation thatfadedrapidlyandwasitselfnebulous.When as far87Leonis.Thecomethadfadedsadly,however,since to xVirginis,orfor32.Thoughveryfaint,itwasnoticeable strong condensation,wasveryilldefinedand blurred. the nucleuswasbeautifullystarlike,andimbeddedinaverystrong 17. TheentirecometwasfainterthanonJune6.head © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm hm hm hm hm At 825itwasquiteconspicuousinthe5-inchtelescope,with June 7.At940thetailwasfaint,butcouldbetracedto87 June 6.Atabout827thecometbecamevisibletonaked In the5-inchtelescopenonucleuswasvisible.Thereonly June 9.Atio35theskywasmurky and brokenwith The cometwasfirstvisibleinthefinderof40-inchat8. E. BARNARD 1914ApJ 39. . 37 3B © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm io-inch Lens.June6,i549G.M.T.Exposurei2o Scale: icm=o?44

PLATE XII

North 1914ApJ 39. . 37 3B hm hm hm glasses, withwhichperhapsfainttracesofthe tailcouldbeseen. be seenwiththenakedeye,butitwasquitenoticeable inthefield- scope, wasveryfeebleandtoofainttoattempt anexposure. longer befollowed.Theskywasverygood. The cometcouldnot rather smallanddiminthe5-inchtelescope. By 952itcouldno 942 itbecametoofaintindensehazetoguideonwiththe5-inch. magnitude. Itwasnotcertainlyseenwiththenakedeye.At visible inthe5-inchtelescope.Thecometwasveryfaintanddim diameter. Theskywasthickandbrightwithstrongmoonlight. which diffusedintothegeneralnebulosityofhead.Thenucleus strongly condensedwithnonucleus,andwasperhapsoftheeighth throughout theexposures. with moonlight. little lessbright,butwasdefinite.Theskyverywhite magnitude 10=«=;seeAstronomicalJournal,27,149,1912),ora was ofaboutthesamebrightnessascomparisonstar(estimated stellar andaboutone-halfmagnitudelessthanthecomparisonstar naked eye. intervals forperhapshalfanhour.Theheadalonewasvisibleasa stellar. Itwasplacedinasmalldensenebulosity5"diameter, covering theplacesothatexposureswerebadlyinterrupted. dim hazystar,andwasonlyjustseenwithcertainty.Cloudskept 1912). Itwasinthecenterofastrongcondensationabouti' shining. Fromabout9i5thecometcouldbeseenfaintlyat a traceoftail.Itwasveryfaintinthe5-inchtelescope.. with thenakedeye,butlateritcouldbeseenfaintly,possibly (estimated magnitude9.5-10;seeAstronomicalJournal,27,149, © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem hm hm hm hm June 27.At9othecomet,thoughseenin the5-inchtele- June 25.At840itwasofabouttheeighth magnitudeand June 24.At9iointhe5-inch'cometwassomewhat June 15.Onlythefaintnucleusandcentralcondensationwere June 14.Withthe40-inchtelescopenucleuswasalmost June 12.Inthe40-inchnucleuswasveryilldefined—not A faintsmallnucleuscouldbeseeninthe5-inchtelescope. This wasthelastdateonwhichcometseenwith June ii.Theskywasclearatdarkbutacrescentmoon June 10.Crescentmoon.At847.thecometwasnotvisible VISUAL OBSERVATIONSOFBALLETSCOMET 403 1914ApJ 39. . 37 3B physical SocietyofAmerica. 4O4 report oftheCometCommitteeAstronomicalandAstro- the Brucephotographictelescopeisgivenincatalogueof contains thegreatestlengthsoftailasseenwithnakedeye during theseobservations. © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem A listofthephotographsobtainedwithvariouslenses For theconvenienceofthoseinterestedinmatter,TableII Yerkes Observatory Williams Bay,Wis. March 7,1914 30 June i May 3 T GREATEST VISIBLELENGTHOFTHETAIL 27 29 26 25 18 I? 14 24 9 4 6 9 6 5 7 Date E. E'BARNARD TABLE II Length ofTail 0 I 107 120 ormore .1 7°-i8 33 47 52 65 53 S 32 54 17 -18 53 iS 29 iS 17 25 . Onhazysky On poorsky On verybadsky