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

205 Pages·2011·2.84 MB·English

by  Robert L. Clark (auth.)

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
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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