Upgradingthe30-inchTelescopeatLindenObservatory

RobHorvat(WSAAG)NACAAXXVII:Easter2016

The30inchTelescopeComestoLinden

1997.UnderthedirecPonoffamedsupernovahunterandLindentrusteeBobEvans,the30inchStarspliUerTelescopewasshippedfromtheUSAtoprovideareallylargetelescopeforuseatLindenandtobeafocusforobservaPonalastronomythere.ItwasrecognisedthattheBeames24inchprobablycouldnotbeusedinitspresentconfiguraPonbythepublic-forsafetyreasons.

Bob Evans with his 16inch Dob atLinden(2006)-picturebyNickLomb.

The Beames 24inch is a “bent cassegrain” design: 152mm secondary at top and asmallopPcalflatintheboUomtube.Eyepieceswereinsertedtothesideofthetube.

30inchtelescopeshedonle_.Beamesdomewith24inchtelescopeonright.

WSAAGMembersBecomeCaretakersofthe30inchThe30inchtelescopebecamelessusedoverPmeandwasinneedofsomeaUenPon.LindenTrusteeBobEvansremarked:“the30inchtelescopeneedssomebodytoloveitandtouseit”.October2012.WSAAGexpressedinterestinoperaPngthetelescope.AsprimarilyDobusers,BobmadeGerryFlanaganandInewcaretakersofthescope.

OldOpPcalSpecs

Primarymirrordiameter: 30inch(762mm).Primarymirrorfocallength: 132.5inch(3362mm).Primarymirrorweight: 44kg.FocalraPo: f/4.42.Secondarymirrorsize: ~5inch(125mm).

• Manualwinchtorolltheshedoffwasslowandlabourintensive.• Baseofshedwasinneedofrusttreatment.• Concreteslabwasnotwideenoughforladders.Thiswasamajorsafetyconcern.• EQplajormwasabitofalemonsothescopewasessenPallymanuallyoperated.• Notenoughin-focusforseveraleyepiecese.g.Ethos21mm.• Straightthroughfinderscopeatthetopofthescopewasafallrisk.• ScopeneededfrequentcollimaPon.SomePmesmorethanonceinanight’sviewing.

EarlyIssueswenotedwiththeShedandScope

• Old 2-wheel wooden ladder was unusable. Metal 3-wheel step ladder wascumbersome,couldroll-awayand,atPmes,hadtobejimmiedovertherails.• Scopecouldbepointedbelowhorizontal!riskofprimarymirrorfloppingforward.• Primarymirrorwasnowsome18yearsoldandwell-overdueforarecoat.

ARight-anglefinderscopewasplacedlowertofrontofscope(relocatedagainlater).OriginalfinderscopesPllaUachedinphotobelow.Note:low-profilerackandpinionfocuserwithnofinefocus.

SomeIniPalSoluPons

Low-elevaPonstopaddedtorockerbox.

Gorilla0.8mStepLadder.

Gorilla1.8mPlajormLadder.Spring-loaded wheels wereaddedlater.

NewLadders:

Red lights were added totheboUomofbothladders.

A 12V boat winchwas purchased tomovetheshed.

EarlyMay2013-Theconcreteplajormaroundthe30inchwasextended.Layingtheconcretewastrickyaswewantedthesmallestgaple_nexttotherailsthatwouldsPllallowtheshedtorolloff.

TheConcretePlajormisExtended

TrusteeIanBridgesinspectsthearea.

The0.8mstepladderand1.8mplajormladdercanbele_atanycornerwithoutinterferingwiththemovementofthescope.

FindingObjectsbeforetheArgoNavisandServoCATInstallaPons

TheEVANS30”Telescope(T-Rex)wasupgradedbySDMTelescopes

midMay-earlyJune2013

May2013.The30”telescopewasstrippeddownandpackedbyadedicatedcrewofWSAAGmembersunderthecompetentsupervisionofDaveGault.ItwasferriedtoSDMTelescopesBunbartha(Victoria)byDaveGaultandmyself.

TonyBarry,AlanPlummer,LachlanDavis,DaveGault,PeterNosworthy

DaveGault,PeterRead,RobHorvatatPeterRead’sresidence(SDMTelescopes),Bunbartha.

EarlyJune2013.ThescopewasreturnedtoLindenbyPeterRead.PhotoscourtesyofKimRead.

• Newpoweredgroundboard(EQplajormdiscarded)• FullServoCATGOTOwithArgoNavisand10Kencoders• New27pointstainlesssteelmirrorcellwithcablesling• 2.5inchFeathertouchfocuser

TelescopeUpgrades–PeterRead

The trusses were also shortenedtoprovideabeUerrangeoffocusfor eyepieces and some videocameras.

At some Pme in the future, wewill replace the 5inch secondarymirrorwitha5.5inchmirror.

Whenupright, thescope isaboutonefoot(30cm)lowertotop.Theold EQ plajorm added about20cmtotheheight.

This also improves safety on thetall ladders as we don’t have tostandashigh.

InhonourofBobEvans,thescopewasofficiallynamedTheEVANS30”Telescope.Previously,ithadamorecasualnameofT-Rex.DecalsbyPeterRead.

StalkwithArgoNavishandpad(blue)andServoCAThandpad(black).

ThetopendofthescopealsohasawirelessServoCAThandpad.Peter moved the boards with Finderscope, Telrad & ServoCAT handpadclosertothefocuserforbeUeraccess.

2.5inchFeatherTouchFocuserwitha10:1reducPonfinefocusknob.

SkyFiwirelessadapterinrockerbox.ThescopeisrouPnelycontrolledusingSkySafarionaniPad.

AfloataPoncellshouldbedesignedsothatallpointssupportthemirrorevenly.Oldmirrorcell(le_photo)–• Manyofthetriangularpieceswerelocked(theyshouldswivel)andnonewereflat.• Trianglesofthesamesizewereofdifferentthicknesses.• SomehadthewrongproporPonswiththeboltholeinthewrongplace.Netresult:notalltheteflonpadswereinpropercontactwiththemirror.Fabricslingsupportedmirrortoonly140degreesofcircumference.

Petermadeupacompletenewcageandcellofstainlesssteeltriangles(rightphoto).Thestainlesssteelwireslingsupportsthemirrorto180degreesofcircumference.

AdapterswereconstructedbyTonyBarryand Dave Gault to insert a Point GreyFlea3videocameradownthe2”focuserandaGrasshopperExpressvideocameradown the 2.5inch focuser when using a0.5xfocalreducer.

The scope was one of a largeconPngent used for the PlutooccultaPon of June 29th 2015 justpriortotheNewHorizonsflyby.

The Grasshopper Express camerawasrunbyDaveGaultat7.5framespersecond.

Flea3inthe2inchadapter

Grasshopperin2.5inchdrawtube

NGC1566-TakenbyTonyBarryinOct2014usingtheEvans30”andGrasshopperExpress.

SupernovaASASSN-14ha,mag14.6,clearlyseenatcentreintheinsetatboUomright.

Stackof100imagesat2secseach.Nodarks,flatsorpostprocessing.

Thesupernovacouldalsobespiedvisuallyinthetelescope.

TPAS

The Argo Navis can be used to improve telescope poinPng using its inbuiltTelescope PoinPngAnalysis System (TPAS). The system can, for example, takeintoaccountthegravitaPonalflexureofthescope.

Thetwomostusedeyepiecesinthetelescopeare:21mmEthos!160xandTFOV~38’13mmEthos!260xandTFOV~23’

Withoutanydefinedmodel,aslewtoanobjectwillusuallyput itsomewherewithinthefieldofviewofthe13mmEthos(radius~12’).

ManyhourswerespentbyGerryFlanaganandIdevelopingapoinPngmodel.Ifweneedto,wecanperforma6-staracquireandpoinPngwillusuallybewellwithin6’ofthetarget.

AnUnexpectedProblem

In November 2013, we experienced some issues where thescopewouldseeminglystopwhenslewingtoanobject.Atestwithasetofscalesshowedittook3.2kgofforcetopullthescoperoundfromthetopend.The scope is heavy. Peter Read and Dave Gault surmised thatthegroundboardmayhavedished.Dave had a shim assembly made-up to li_ the centre of thegroundboard.

Result:thescopenowonlytakes1.5kgofforcetopullaroundfromthetop.Recenttestsindicatethishasnotchanged.

SpareSecondary

DaveGault and I replaced thedegraded5inch secondary (le_)with the sparefromthemainshedatLindeninMarch2015.

TheEVANS30”primarymirrorwasre-coatedearlyJuly2015.

Evans30”DisassembledandMirrorPacked

EarlyJuly2015.PeterReadarrivedaround8:45am.

Westrippedthescopedownandremovedtheprimarymirror.The velcro, which centered the sling around the mirror, wasn’t too hard to get off.EucalyptusoilgotthesPckierbitsofglueoff.

WehadthemirrorpackedintoPeter'scrateby9:40orso.Lessthananhouranditwasonitswaynorth.

WSAAGworkcrew:PeterNosworthy,JohnBellingham,SelYusuf,AlanPlummer,me.

TherecoatwasdonebyWayneSaintyofSaintechIonBeamSystems,Taree.PhotoscourtesyofPeterRead.

Evans30”mirrorgoingintochamber

30”mirrorrotaPngface-downandcoatedwithvapourisedaluminiumionsinvacuumchamber

PhotoscourtesyofPeterRead.

Coated30”mirrorbeingli_edout.Noteclamparoundmirror.

AproudWayneSaintyphotographshiswork.AssistantDavidremovingclamp.

PhotoscourtesyofPeterNosworthy.

Evans30”MirrorBackandScopeReassembled

WSAAGworkcrew:PeterRead,TonyBarry,LachlanDavis,DaveGault,PeterNosworthy,SelYusuf,me.

SowhatwastheImprovementachievedbytheRe-Coat?

Expert variable star observer Alan Plummer did a number of limiPng starmagnitudetestsbeforeanda_erthere-coaPngofthemirror.

14/3/15,oldopPcs.AchartforthevariablestarCGCanisMajoriswasused.Astarofmagnitude15.3couldbeseen.Mag16.0couldnotbeconfirmed.19/3/15,oldopPcs.Thesamefieldasabove,withtheskyaliUlebeUerthanonthe14th.Astarofmagnitude16.0wasdefinitelyseen,butnot16.223/5/15,oldopPcs.ThefieldofRScorpiiwasused,withM80inthefield.Astarof15.8magcouldbeseen.

12/9/15,newopPcs.ThefieldofVYSculptoriswasused.Astarofmagnitude17.1couldbeseen.3/10/2015,newopPcs.TheVYSclfieldwasusedagain.Magnitude16.6wasclear,the17.1wasnotconfirmed.

“This isaveryroughandreadytestofatelescope’sopPcs. ItwouldbebeUerifthere were many more observaPons both before and a_er the work on themirrors. However, unlike many modern large telescopes, the point of thisinstrumentisforpeopletolookthrough.

So fromthatpointofviewthis test is reasonable.Beforetheworkwehaveanaverage limi>ng visual magnitude of 15.73, and aFer we have 16.85. Andremember that a1magnitudedifference is adifference in light intensityof 2.5Pmes.”

AlanPlummer

TheEvans30inchTelescopeToday

ThegreatthingaboutthisbigDobisthatitsitsatareasonablydarksitenottoofarfromSydneyand that it is available for visualobserving. It gets lotsofuse in thisregard. IneverPreofthefantasPcallyresolvedviewsofSaturn,47TucorthetwolobesoftheHomunculus.TheTarantulaisjustspectacular.Andyoucanseedetailingalaxiesthatmy12inchDobjustcan’tgrasp.

Thescopepointsandtrackswellandiso_enusedforeventslikeoccultaPonswherethetargetsaretoofaintforthesmallerscopes.

ManythankstotheLindenTrustfor the use of the scope andtheir conPnued support in thisventure.I think we havemade this intoone of the best telescopesaround for use by amateur (orprofessional)astronomers.

MilkyWayoverLinden.PhotobyNarayanMukkavilli.Oct2015.