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Amateur Telescope Making in the Internet Age: Finding Parts, Getting Help, and More PDF

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Patrick Moore’s Practical Astronomy Series Forfurthervolumes: http://www.springer.com/series/3192 Amateur Telescope Making in the Internet Age Finding Parts, Getting Help, and More Robert L. Clark 123 RobertL.Clark Westminster,MD21157,USA ISSN1431-9756 ISBN978-1-4419-6414-4 e-ISBN978-1-4419-6415-1 DOI10.1007/978-1-4419-6415-1 SpringerNewYorkDordrechtHeidelbergLondon LibraryofCongressControlNumber:2010935731 ©SpringerScience+BusinessMedia,LLC2011 Allrightsreserved.Thisworkmaynotbetranslatedorcopiedinwholeorinpartwithoutthewritten permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY10013,USA),exceptforbriefexcerptsinconnectionwithreviewsorscholarlyanalysis.Usein connectionwithanyformofinformationstorageandretrieval,electronicadaptation,computersoftware, orbysimilarordissimilarmethodologynowknownorhereafterdevelopedisforbidden. Theuseinthispublicationoftradenames,trademarks,servicemarks,andsimilarterms,eveniftheyare notidentifiedassuch,isnottobetakenasanexpressionofopinionastowhetherornottheyaresubject toproprietaryrights. Printedonacid-freepaper SpringerispartofSpringerScience+BusinessMedia(www.springer.com) Acknowledgments Many people should share in the credit or blame for this book, some for direct contributionsandsomeforencouragementandsupportoftheactivitiesleadingup tothisbook. Of the first group my wife, Nancy, tolerated lots of things not getting done as timewenttothebook.Shecopiedfilesandpictures,providingneededtechnicalsup- port.GerryFrishkornfromtheWestminsterAstronomicalSocietyprovidedtheneat photoofaspiderfromhisfamousbinoculars.Healsocheckedanddetectederrors in my math. Numerous folks from the same club provided leads for the supplier appendix. Cousins Ann Herbert and Faith Marchal provided help with the conver- sion material. Cousin Hughes Gemmill gave me some old Dallmeyer lenses with whichIlearnedhowtogetthemungluedandcleaned. In the second group are Duane Shie, who is inspiring as a dumpster diver; GeorgeLockwood,whowasalwaysavailableforideatestingandeBayhints;Teresa Rosales;BlasChavez;RogerBaker;andMarkDennis,whohelpedwiththelugging oftelescopesandtheirparts. The folks at Springer publishing have been very tolerant of the questions of a beginningauthorandhaveprovidedimportantguidelines. v Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Tools. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 AbsolutelyNecessary . . . . . . . . . . . . . . . . . . . . . . . . 3 VeryHelpfulorNecessaryforParticularTasks . . . . . . . . . . . 3 NicetoHave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Ergonomics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 What’sNotIncludedinthisBook. . . . . . . . . . . . . . . . . . . . 5 GeneralAdvice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 SafetyTips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2 ToBuyorBuildaTelescope . . . . . . . . . . . . . . . . . . . . . . 9 3 TelescopeTypesandDesigns . . . . . . . . . . . . . . . . . . . . . 19 TelescopeTypes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 ReflectorTelescopes . . . . . . . . . . . . . . . . . . . . . . . . . 19 RefractorTelescopes . . . . . . . . . . . . . . . . . . . . . . . . . . 21 TelescopeDesignConsiderations . . . . . . . . . . . . . . . . . . . . 22 ARealSimpleTelescope . . . . . . . . . . . . . . . . . . . . . . . . 27 4 BuildaGoodCopyscope . . . . . . . . . . . . . . . . . . . . . . . 33 TheSmallCopyscope . . . . . . . . . . . . . . . . . . . . . . . . . . 33 OpticalParts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 MechanicalParts . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 TheMediumCopyscope . . . . . . . . . . . . . . . . . . . . . . . . 35 OpticalParts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 MechanicalParts . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 TheLargeCopyscope . . . . . . . . . . . . . . . . . . . . . . . . . . 36 OpticalParts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 vii viii Contents MechanicalParts . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 HowtoMakeYourCopyscope . . . . . . . . . . . . . . . . . . . . . 38 FocalLength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 MountingaCopyscope . . . . . . . . . . . . . . . . . . . . . . . . . 42 5 The80mmRefractor . . . . . . . . . . . . . . . . . . . . . . . . . 45 TelescopeDescriptionandCapabilities . . . . . . . . . . . . . . . . . 45 SpecificationsandComponents . . . . . . . . . . . . . . . . . . . 46 6 NewtonianTelescopes . . . . . . . . . . . . . . . . . . . . . . . . . 57 TypicalNewtonianTelescopes . . . . . . . . . . . . . . . . . . . . . 57 TheObjectiveMirror . . . . . . . . . . . . . . . . . . . . . . . . . . 59 MirrorMounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 ASpiderinYourTelescope . . . . . . . . . . . . . . . . . . . . . . . 65 MirrorCells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 SimpleCollimation . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 7 TheF174-InchRefractor . . . . . . . . . . . . . . . . . . . . . . . 73 TheRotatingStarDiagonal . . . . . . . . . . . . . . . . . . . . . . . 74 TheBackTwoBulkheads . . . . . . . . . . . . . . . . . . . . . . . . 75 TheDiagonalMirror . . . . . . . . . . . . . . . . . . . . . . . . . . 77 MountingtheRefractorUsingaCradle. . . . . . . . . . . . . . . . . 81 8 Focusers,Eyepieces,Barlows,andFinders . . . . . . . . . . . . . 83 Focusers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 TelescopingTubes. . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 RackandPinionDesign. . . . . . . . . . . . . . . . . . . . . . . . . 85 HelicalDesign. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 CrayfordDesign. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Eyepieces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 EyeRelief . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 ExitPupil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 Achromats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 VeryModernWideAngleEyepieces . . . . . . . . . . . . . . . . . . 90 CompoundProjectionandCameraLenses . . . . . . . . . . . . . . . 91 BarlowLenses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 ImageInverter(ErectingLens) . . . . . . . . . . . . . . . . . . . . . 93 Finders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 RequirementsforaWorkableFinderScope . . . . . . . . . . . . . . 94 SatisfyingtheFinderRequirements. . . . . . . . . . . . . . . . . . . 95 PeepSightFinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 LaserPointerasaFinder . . . . . . . . . . . . . . . . . . . . . . . . 99 9 Tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 ClosedTubeApproaches . . . . . . . . . . . . . . . . . . . . . . . . 102 WoodenTubes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Contents ix GettingStarted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 AssemblyoftheTube . . . . . . . . . . . . . . . . . . . . . . . . . . 106 UsingGussets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 WoodTubesWithoutGussets . . . . . . . . . . . . . . . . . . . . . . 110 OpenTubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 TrussTubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 10 Buildinga12.5-InchNewtonianwithRotatingCage . . . . . . . . 113 DimensionsoftheTube(Box) . . . . . . . . . . . . . . . . . . . . . 114 Diagonal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 Spider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 UpperTubeRotation . . . . . . . . . . . . . . . . . . . . . . . . . . 121 DoughnutstoPreserveAlignment . . . . . . . . . . . . . . . . . . . 121 Stabilizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 11 ErgonomicMounts . . . . . . . . . . . . . . . . . . . . . . . . . . 127 MountingTypes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 Supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 BalanceandMoment . . . . . . . . . . . . . . . . . . . . . . . . . . 129 Wedges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 AnErgonomicAltazimuthMount . . . . . . . . . . . . . . . . . . . 133 12 Evaluation,QualityTesting,andOpticalAberrations . . . . . . . 137 HowGoodDoesItNeedtoBe? . . . . . . . . . . . . . . . . . . . . 137 CommonFaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 FocalLength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 QualityTesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 PossibleConstructionProblems . . . . . . . . . . . . . . . . . . . 140 Lenses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 Mirrors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 MirrorReflectiveCoatings . . . . . . . . . . . . . . . . . . . . . . 142 OpticalQualityTerminology . . . . . . . . . . . . . . . . . . . . . . 142 Wavelength-BasedMeasurements . . . . . . . . . . . . . . . . . . 143 RaysandWaves . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 ScratchandDigOpticalSurfaceSpecifications . . . . . . . . . . . 146 Scatter(Spot)Diagrams . . . . . . . . . . . . . . . . . . . . . . . 146 StrehlRatio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 Qualityof“Flat”Mirrors . . . . . . . . . . . . . . . . . . . . . . . 148 TestingaFlat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 OpticalAberrations . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 QuickandEasyTests . . . . . . . . . . . . . . . . . . . . . . . . . . 152 13 JunkCollectingandWorkingwithModernMaterials . . . . . . . 153 JunkCollection(CreativeCrossUtilization) . . . . . . . . . . . . . . 153 LensRestoration/UsedLenses . . . . . . . . . . . . . . . . . . . . . 155 LensCementing . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 x Contents GettingaLensApart . . . . . . . . . . . . . . . . . . . . . . . . . 156 PolishingandCoatingIdeas . . . . . . . . . . . . . . . . . . . . . . 157 NoDrag,NoProgress . . . . . . . . . . . . . . . . . . . . . . . . . . 158 HowLongWillItTake? . . . . . . . . . . . . . . . . . . . . . . . 158 LapMaking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 WorkingwithPVCPipe . . . . . . . . . . . . . . . . . . . . . . . . 161 PVCEyepieceCanisters . . . . . . . . . . . . . . . . . . . . . . . 163 ForNCanisters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 OtherUsesforPVC . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 AligningParts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 TelescopeMounts . . . . . . . . . . . . . . . . . . . . . . . . . . 165 LensCells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 RetainingRings . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 FloorUnderlay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 GluesandCements . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 AppendixI WebSuppliersofTelescopeBuildingParts andMaterials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 AlphabeticalListingofSuppliers . . . . . . . . . . . . . . . . . . . . 170 Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 SupplierCodesbyProduct . . . . . . . . . . . . . . . . . . . . . . . 188 AppendixII Telescope-BuildingBooksandWebsites . . . . . . . . . . 193 BookMust-Haves . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 Magazines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 Websites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 AppendixIII PolishingLog. . . . . . . . . . . . . . . . . . . . . . . . . 197 AppendixIV UnitsandConversions . . . . . . . . . . . . . . . . . . . 199 GeneralConversions . . . . . . . . . . . . . . . . . . . . . . . . . . 199 WoodStockandHardwareConversions . . . . . . . . . . . . . . . . 199 EuropeanPlywoodStandards . . . . . . . . . . . . . . . . . . . . 199 Timber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 About the Author Although Clark was born in New Hampshire, he spent his early teen years in the New York City area. There he became acquainted with the Theodore Roosevelt MuseumofNaturalHistoryandattheassociatedHaydenPlanetarium,operated,at thattime,byNewtonandMargaretMayhall.TheirbookSkyshootingprovidedhis firstintroductiontotheideathatsomeonewithonlymoderateskillscanbuildgood scientificinstruments.ThethreevolumesofAmateurTelescopeMaking,editedby AlbertG.Ingalls,completedtheprocessofaddiction. Clark received a B.S. degree in Mathematics from Stanford University. He then served in the US. Air Force at Strategic Air Command headquarters in Nebraska. After his discharge he did graduate work in Mathematics and Computer Science at the University of Maryland. After a few years spent in the Military Operations Researchindustry,hemigratedtoauniversityteachingpositionthatlasted33years attheUniversityoftheDistrictofColumbia. Throughout all this time he continued to be enamored by the process of build- ing telescopes and actually built a few as time permitted. Since retirement he has allowed the addiction to occupy a large part of his enthusiasm, as is made evident byFig.2.3. Clark now resides in Westminster, Maryland, where he has built a hilltop observatoryandisactivewiththeWestminsterAstronomicalSociety. xi

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The Internet Age is changing everything about human invention and the use of technology. The change has been compared to that of the introduction of printing. Making your own telescope isn’t what it used to be, either, thanks partly to the Internet. The old days of grinding and polishing are gone
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