Brunson 771 - Pointing the Telescope; Installing Lighting Accessories

Model 771, 75, and 76-RH190 Transits 12
other,orcollimated.
Thefocusknobonthetelescopehasan
indicatorofthedirectionyoumustturn
ittofindinfinityfocus,butyoucan’t
justturnitallthewayinthatdirection
andexpecttothetelescopetobefo‐
cusedatinfinity.
Theeasiestwaytofindtrue“infinity
focus”istoholdanopticallyflatmirror
(suchasourmodel185)rightup
againsttheobjectiveendofthetele‐
scope.Turnonthetransit’sinternalillumination(see“Installing
lightingaccessories”below).Turnthefocusknoballthewayinthe
directionofinfinity(indicatedontopofthefocusknob).Then,turn
theknobslowlyintheoppositedirection,andwatchcloselyforthe
reflectedimageofthereticle.Itcangobyprettyquickly,sogoing
slowlyisimportantwhilelookingthroughthetelescope.Onceyou
havefocusedthetelescopesothatyoucanclearlyseethereflected
reticleimage,youknowthatthetelescopeis,bydefinition,focused
atinfinity.



Releaseboththehorizontalandverticaltangentclamplocks,and
movetheinstrumentbyhand.Precisepointingisaccomplishedby
re‐lockingbothclampswhenyougetclosetothetarget,andthen
turningthetangentadjustmentscrewsforpreciseplacementofthe
reticle.Bothtangentadjustmentscrewsareoutfittedwithwobble
pinswhichallowforsmoothtranslationoftheaxes.Thefinalset‐
tingshouldbemadebyturningthetangentscrewinaclockwise,or
pushing,direction.Thiswilleliminateanypotentialsubsequent
movementduetofrictionofthespring‐loadedplungerswhichop‐
posethetangentadjustmentscrews.



Forcertainproceduresthatwewilldiscussinthismanual,(e.g.,col‐
limation,autocollimation,andreticleprojection)itisnecessaryto
illuminatethereticleofyourtransitfromtheinside.A
model76‐x
transithastworeticles(oneinthemaintelescopeandoneinthe
cross‐axistelescope)whichmayneedtobeilluminated,depending
uponwhatyouaredoing.

Illuminatingthecross‐axistelescopereticle.Yourtransitcomes
equippedwithalightsourceforthecross‐axistelescope(model76‐
Thereflectedimageofa
reticle(here,located
aboveandtotherightof
center)willappearonly
atinfinityfocus.
Figure2.7
Installinglightingaccessories
Pointingthetelescope