Affordable DSO Astrophotography

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Affordable DSOAstrophotographyCraig Stark, Stark LabsMonday, November 23, 2009


Typical advice: Think big or go home“To really start doing astrophotography, you’re going toneed a solid mount. Don’t even think about trying thiswithout something like a G-11. ... lesser mounts justaren’t up to the task... GOTO is also a real help”Losmandy G-11 withGemini GOTO: $3200Can we get the mount, scope,and camera for ~$2000?Monday, November 23, 2009


$49,000 QuestionMonday, November 23, 2009


Michael FulbrightGSO 8” f/4, Baader MPCC, Canon Rebel XT, AtlasMonday, November 23, 2009


Tony HitchcockMeade LXD55 SN10, Baader MPCC, Canon 300DMonday, November 23, 2009


Jim SolomonCelestron C8-N ASGT, Baader MPCC, Canon Rebel XTMonday, November 23, 2009


Garrett GraingerOrion ED80, Canon Rebel XT, Orion Sirius EQ-GMonday, November 23, 2009


Mel Wurth8” f/5, Canon Rebel XTi, Atlas EQMODMonday, November 23, 2009


Scott AnttilaHPN 8” f/5, MPCC, Canon Rebel XT, ASGTMonday, November 23, 2009


Chuck KimballExplore Sci 152, Canon Rebel XT, on LX200 classicMonday, November 23, 2009


Chuck KimballExplore Sci ED80, Canon Rebel XT, on LX200 classicMonday, November 23, 2009


Chuck KimballOrion 6” Newt, Canon Rebel XT, on LX200 classicMonday, November 23, 2009


Stephen HamiltonMeade LXD-75 SN8, Meade DSI Pro IIMonday, November 23, 2009


Moral: Throwing money at it isn’tnecessary & won’t always helpBetter equipment does not ensure better images.Excellent images can be had from relatively affordableequipment.Learning how to image and process / learning how to bestuse your gear and software as big if not bigger factors thanequipment cost.That said, not all affordable equipment is good. How dowe choose affordable equipment that won’t limit us?Monday, November 23, 2009


RoadmapTelescope: Keep the focal length ~1000 mm or less80 mm ED refractorNewtonian or Schmidt-Newtonian (Mak-Newt)MountMass-market GOTOAutoguidedCameraGarrett GraingerBasic DSLRSmaller-chip dedicated camsSoftwareFreeware / inexpensiveMonday, November 23, 2009


Telescope: Think short and/or smallFocal lengthAim for ~2 (1.5 - 3) arcsec / pixel (Your skies won’t give youmuch more than this in any case).WeightAs light as possible. Really.No, really.Monday, November 23, 2009


Telescopes: Short and sweet8” f/5 Newtonian (Synta, Orion, Antares, Celestron)OTA: $290-$4008” f/4 Newtonian (e.g. AstroTech 8” f/4, used GSO)OTA: $45080 mm ED Refractor (Orion, Skywatcher, WO, AstroTech, SV)OTA: $550-$70066 mm ED Refractor (WO, AstroTech)OTA: $330-360Monday, November 23, 2009


Newt Pros: Lots of photons, nofalse color, and inexpensiveNo chromatic aberrationNo purple haloNo IR-induced star bloatLight Gathering vs. Size8000600040002000By far, biggest aperture per $03” 4” 6” 8”SNR in DSO images driven heavily by aperture.Available in focal lengths well-suited to current camerasMonday, November 23, 2009


Newt Cons: Size and comaCons:Weigh more than SCT OTAs or small refractorsBigger target for windTubes prone to flex with heavy camerasDifficult to use focal reducers withCollimation a mustComaMonday, November 23, 2009


Newt Cons: Size and comaCons:Weigh more than SCT OTAs or small refractorsBigger target for windTubes prone to flex with heavy camerasDifficult to use focal reducers withCollimation a mustComaMonday, November 23, 2009


Coma is driven by position & f-ratio~1 Pixel at corner of 1/3” chipf/43 mm11μ6 mm24μf/53 mm7μ6 mm15μ9 mm36μ12 mm49μ15 mm62μ9 mm23μ12 mm31μ15 mm40μTo use a Newtonian with a reasonable focal length, weneed to tame the coma on many chips (esp. DSLRs)Monday, November 23, 2009Images from James Mulherinhttp://www.opticalmechanics.com/about_coma.htm


Two good coma corrector choicesBaader MPCC$144No shift in focal lengthBig chips: f/4 limit, cleaner at f/5TeleVue ParaCorr$220 & $310 (Photo vs. Visual)Extends focal length by 15% (f/4→f/4.6)Big chips: Good to f/3.5Monday, November 23, 2009


Baader MPCCCorner of Trifid2(~12 mm) at f/4.6Corner of HX-916 (~5.5 mm) at f/4Images from Tom Lichahttp://www.licha.de/astro_review_mpcc.phpImages from Christope Demeautishttp://demeautis.christophe.free.fr/test/baader/baader.htmMonday, November 23, 2009


Short refractor pros: Wide field, lightweight, & super-easy guidingShort focal lengths (400-500 mm)Let you go WIDE even with smaller chipsGuiding is easy ... really easy.Light weight is easy on the mountTube flex much less an issueMonday, November 23, 2009


Short refractors cons: Samplingrate, color, and non-flat fieldResolution is a bit limited400 mm, 6 u pixels = 3” / pixelSmall targets won’t show as much detailChromatic aberration in doubletsField is not typically flatAstrotech & Hotech flatteners, TV and WO reducers, ...Monday, November 23, 2009


Think small scopes can’t go deep?Monday, November 23, 2009


Think small scopes can’t go deep?Monday, November 23, 2009


Think small scopes can’t go deep?Monday, November 23, 2009


Think small scopes can’t go deep?Monday, November 23, 2009


Image Sampling: 400 vs. 1000 mmMonday, November 23, 2009


Image Sampling: 400 vs. 1000 mmGoing very wide will limit resolution (but for manycams, going much above 1 m won’t gain much)Monday, November 23, 2009


Other options8” SCTFocal reducer required (yet still only gets you to ~1300 mm)Not big-chip friendlyAstroTech 6” or 8” RCExplore Scientific “Comet Hunter” 150 Mak-NewtMeade SN-8 and Orion 190 mm (if on an EQ6 / Atlas)Whatever you have if it’s a reasonable focal lengthMonday, November 23, 2009


What spending more gets you:Stability and size of usable FOVMechanics:Most focusers on these scopes have real issues with flex asthe camera weight goes up.Newt OTAs likewise have flex issues w/heavier cameras.Overall precision / repeatability, etc.Size of corrected or correctable field can be limitedNone pull APS-size w/o correction and APS is as big asyou’ll get corrected.Color purity on ED doubletsMore aperture and more photons cost more money.Monday, November 23, 2009


Affordable GOTO mounts existCelestron ASGT: $575 (new)Bundled with scopes like the C8-N 8” f/5Meade LXD-75: $600 (new)Bundled with scopes like the SN-8 8” f/4Celestron CGEM / Orion Atlas / EQ-6$1400 - $1500Heavier payloadMonday, November 23, 2009


Rules of affordable mountsDo not overload the mountOTA < 20 lbs for ASGT / LXD-75OTA < 35 lbs for AtlasGuideBalance set to just slightly east (resisting RA drive)Adjust / tune up as neededEliminate all flex / loose jointsPolar align reasonably wellPolar scopeIterative GOTODriftMonday, November 23, 2009


Peter KennettMeade LXD-75 SN8, 30 m, Film, Manual guidingMonday, November 23, 2009


Tuning / adjusting is straightforwardand strongly recommendedASGT / LXD-75 / CG-5http://www.astronomyboy.com/cg5/http://www.lxd55.comDIY Kit and ServiceAtlas / EQ-6http://www.beevo.com/rework.htmhttp://www.jamesrobertcook.co.uk/EQ6_dismantle.htmEQMOD: http://eq-mod.sourceforge.net/Monday, November 23, 2009


AutoguidingAll mounts have tracking errors you must account for toimage beyond 10-60s.Use a separate guide scope or an off-axis guider to track astarManualAutomaticSeparate guide camera / chip (same pixels cannot doboth)Computer / mount linkSoftwareMonday, November 23, 2009


Autoguiding HardwareGuide ScopeTypically an inexpensive refractorShorter f/l can work well (e.g. 400 mm)Often doubles as wide-field scope (e.g. William OpticsZS-66 SD doublet)RingsCommunicationStandard USB / serial link + ASCOM (http://www.ascomstandars.org)ST-4 “autoguide” input + ShoeString adapter (http://www.shoestringastronomy.com/)Monday, November 23, 2009


Autoguiding HardwareCameraWebcamsLong-exposure webcams & LPI / NexImageLess-expensive astro-cams (e.g. Meade DSI used or w/scope purchase)Orion Starshoot autoguider1/2”, 1.3 megapixelMonoOnboard ST-4 output$280Monday, November 23, 2009


Autoguding SoftwarePHD Guiding (Free) http://www.stark-labs.comK3CCDTools ($50): http://www.pk3.org/AstroGuideMaster (Free): http://www.guidemaster.deGuideDog (Free): http://www.barkosoftware.comMonday, November 23, 2009


Mike BroussardAtlas EQG, 6 minute, PHDMonday, November 23, 2009


Garrett GraingerAtlas EQG, 6 minute, PHDMonday, November 23, 2009


Monday, November 23, 2009“100 minute” exposure


Monday, November 23, 2009“100 minute” exposure


Michael GarvinCelestron ASGT, HPN 8” f/5, Zhumell 60 refractorCCD Labs QGuide & PHD GuidingRA: 0.16 pixel error (RMS)350mm guide scope, 3"/pixel10.80.60.4Error (pixels)0.20-0.2-0.4-0.6-0.8-11 31 61 91Frame (2s)Monday, November 23, 2009


Michael GarvinCelestron ASGT, HPN 8” f/5, Zhumell 60 refractorCCD Labs QGuide & PHD GuidingRA: 0.48 arcsec error (RMS)350mm guide scope,2.521.51Error (arcsec)0.50-0.5-1-1.5-2-2.51 31 61 91Frame (2s)Monday, November 23, 2009


Flex-induced error is a verycommon source of poor guidingPost-guiding Error302520Setup 1Setup 2Linear (Setup 1)Linear (Setup 2)y = 0.4683x - 1.07861 pixel in 2.1 minPixels151051 pixel in 17 miny = 0.0589x + 0.21760-50 10 20 30 40 50 60 70 80Time (m)Monday, November 23, 2009


What paying more on your mountgets you: Payload & accuracyNeed more than ~30-40 lbs?Want to image at longer focal lengths and higher resolutions?Up to a point, magnitude of PE is not a key concern.Key is how smooth the PE is and how much of it is at ahigh frequency (rapid changes in position).Getting round stars at 1”/pixel (or better) for 5+ minutes isnot trivial and not for the faint of heart (or light of wallet)Monday, November 23, 2009


CamerasOne-shot vs. Mono?Big vs. Small chip?Cooled vs. Uncooled?Big and Color:Canon DSLRs: Canon Rebel XS ($500 w/lens)Orion Starshoot Pro ($1200) and QHY8 ($1500)SmallerAtik 16IC ($590) and 16IC-S ($920) - cooledMeade DSI II ($400) and III ($800)Orion Starshoot II ($300)Many more options used (ICX 285 and KAI-2020 cams)Monday, November 23, 2009


What spending more gets you:Bigger chipsChip costs rise with increasing chip sizeDSLRs are by far the least expensive way to get big chips(mass-production)Short f/l will still get you a wide FOV.Don’t underestimate what will fit on a “small chip”Monday, November 23, 2009


FOV of 8 mm chipsMonday, November 23, 2009


FOV of 11 mm chipsMonday, November 23, 2009


What spending more gets you:Lower noiseCoolingDrops dark current and dark noise to near zero (no darksneeded or very effective dark subtraction)Makes line filter imaging in the summer possible for someLower and cleaner read noiseMany less expensive cameras have structure in the readnoise that cannot be removed with calibration (streaks,bands, etc)Monday, November 23, 2009


Atik 16IC: Adjacent bias framesMonday, November 23, 2009


Atik 16IC: Adjacent bias framesMonday, November 23, 2009


Canon XSi: Adjacent bias framesMonday, November 23, 2009


Canon XSi: Adjacent bias framesMonday, November 23, 2009


Urban M51: 350XT vs. 3 MonoCCDsVery large gap between the monoastro-CCDs and the Canon.Monday, November 23, 2009Stack of 5 best frames, 1 m apiece, no darks.


Monday, November 23, 2009


Urban M51 Rematch: XSi, Color& Mono CCDsColor filters arethe source ofsome of theloss, but alarge gapbetween DSLRand astro-CCD.Monday, November 23, 2009Single 3 m frame, Ambient ~55F, L-data only


Software: ProcessingIRIS (Free): http://www.astrosurf.com/buil/us/iris/iris.htmWindowsVery powerful. Can do most anything to process imagesMostly command-line driven - many find this difficultDeep Sky Stacker (Free): http://deepskystacker.free.fr/WindowsAligning and StackingPre-processing (darks, flats, etc).Monday, November 23, 2009


Capture & ProcessingK3CCDTools ($50): http://www.pk3.org/AstroMeade, LE-webcams, normal webcams, other videodevices, SAC, Artemis/AtikPre-processing & color reconstructionStacking (incl. alt/az)StretchingGuidingAimed more towards capturing than processing.Monday, November 23, 2009


Capture & ProcessingNebulosity ($45-$60): http://www.stark-labs.comCross-platformCanon, Meade, Orion, SBIG, Starlight Xpress, Fishcamp,CCD Labs, SAC, LE-webcams, OpticStar, Artemis/Atik, FLI,Apogee, Atik, ...Pre-processing (incl. Bad Pixel mapping) & colorreconstructionStacking (incl. alt/az, Drizzle, & standard-deviation)Stretching (incl. DDP), Color control, sharpening, etc.Aimed at both capture and processingMonday, November 23, 2009


Photoshop: Even older versions areinsanely usefulBeastly expensive new ($650)Insanely useful and widely used as a result.Older versions: CS, CS2, etc. available on eBay and are farmore affordable.Astrophotography-Specific ActionsNoel Carboni ($20): http://actions.home.att.netPeter’s Actions ($15): http://petersastro.50webs.comExcellent astrophotography-specific tutorialsMonday, November 23, 2009


Alternatives are less expensive buta lot less powerfulGIMP (Free): http://www.gimp.orgCross-platform8-bit/color (32-bit total) onlyhttp://gimp-savvy.com/PIXEL ($39): http://www.kanzelsberger.com/Cross-platform32-bit/color supportPaint.NET (Free): http://www.getpaint.net/8-bit / colorMonday, November 23, 2009


$49,000 QuestionCelestron C8-N ASGTBaader MPCCCanon Rebel XT~$1700 Jim SolomonTakahashi FRC-300FLI ProLine + CFWParamount ME~$50,700Monday, November 23, 2009


MoralBetter equipment does not ensure better images.Excellent images can be had from relatively affordableequipment.Think small and / or short when it comes to the scope andyou’ll have a lot more success (no C14’s at prime on DSLRs).Learning how to image and process / learning how to bestuse your gear and software as big if not bigger factors thanequipment cost.Monday, November 23, 2009

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