Brunson 771 - Collimation for Parallel Sights

23 Operation and Adjustment Manual
bothtelescopes(mainandcross‐axis)willrotateinthe
sameplane,evenifthetransitistiltedfromaverticalori‐
entation(Figure3.7).Forexample,ifyounowlaidthe
entiretransitoveronitsside,themaintelescopeand
cross‐scopewouldstillrotateinthesameplanearound
thecentralaxisofthetransit.Onceyouhaveprecision
plumbedthetransit,proceedtothenextstep.
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3. Autocollimatethemaintelescope.Followthestepspre‐
viouslydescribedtoautocollimatethemaintelescopeto
themirror.However,youmustobserveoneimportant
differencewhenperformingthatprocessthistime.Dur‐
ingtheautocollimationprocess,donotchangetherelation‐
shipofthetelescopetotheverticalspindle.Thatis,leavethe
verticaltangentadjustmentscrewalone—don’tuseitto
tiltthetelescopeforproperautocollimation.Instead,if
youneedtotiltthemaintelescope,usetheleveling
screwsatthebaseofthetransitandtilttheentiretransit
instead.Onceyouhaveachievedautocollimationinthis
manner,proceedtothenextstep.
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4. Turntransittoautocollimatethecrossscope.Itshould
nowbeasimplemattertoturnthetransit90°inorderto
viewthemirrorwiththecrossscope.Rotatethemain
telescope’sfocusknoballthewayinthedirectionopposite
ofinfinity.Thiskeepsthemaintelescope’sfocusingslide
fromobstructingtheviewthroughthecross‐axistele‐
scope.Besurethecrossscopeilluminationisswitched
“on”.Carefullylookintothecrossscopeeyepieceforthe
reflectedreticleimageasyouslowlyturnthetransitback
andforthwiththecrossscopepointedtowardthemirror.
Youshouldnothavetoadjustanything—justrotatethe
upperbodyofthetransittofindthereflectedimage.
Whenyouseeit,youcanbringthereflectedreticleimage
intopreciseregisterwiththecrossscope’sactualreticle
byusingthehorizontaltangentadjustmentscrewtopre‐
ciselyrotatethestandards,and,ifneedbe,theleveling
screwstobringthereflectedimagetodeadcenter.
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Aswehavesaid,parallellight
raysaresaidtobe“collimated”.
Whenatelescopeisfocusedatinfinity,itmeansthatonlyparallel
lightrayswhichareenteringthetelescope’sobjectivelenswillbe
clearlyseenbyanobserverlookingintotheeyepiece.Whenthe
telescopeisfocusedinthismanner,imagesfromcloserthan
ʺinfinityʺareoutoffocus.
Beforewegettoofar,let’sbringupanotherimportantpoint:your
telescopeiscapableofworking“backwards”.Ifyouputalight
Evenwhenthetransitis
tilted,itispossibletomain‐
taina90
°
relationshipbe‐
tweenthemaintelescope’s
lineofsightandthetran‐
sit’sverticalspindle(which
ofcourseisnolongeractu‐
allyvertical).
Collimation