Brunson 771 - Page 40

Model 771, 75, and 76-RH190 Transits 36
Werecommenddoingthesechecksintheorderlistedabove.Per‐
formingthemoutofordercansometimesyieldmisleadingresults.
Forexample,wedescribehowtousefinitetargets(scales)toper‐
formafieldcheckoftheinstrument’shorizontalcollimation.How‐
ever,thehorizontalcenteringmustbeestablishedfirst.Otherwise,
horizontalcollimationtestsareinconclusive.

Wealsodescribea“doublecenter”check,whichisournickname
foraspecialcheckthatcanbeeasilyandquicklyperformed.Ifthe
transitpassesthistest,youcanskipthehorizontalcentering,hori‐
zontalcollimation,plumbline,andmicrometercenteringchecks.

Rememberthatweofferclassesdetailingtheoperationandcalibra‐
tionofourOpticalToolinginstruments.Likeanythingelsethatisa
newexperience,handlingoftheseprecisionmeasurementinstru‐
mentsbecomesmuchfasterandeasierwithalittlepractice.
 Platevialadjustment
 Micrometerbacklash,cen‐
tering,andrange
 “Doublecenter”check
 Horizontalaxisrunout
 Verticalspindlerunout
 Horizontalcentering
 Horizontalcollimation
 Plumblinecheck
 Cross‐axistelescopecolli‐
mation
 Pegtest(coincidencevial)
NOTE:Thismanual
generallypertainsto
the771,75,and76‐
RH190transits.This
chapter,however,fo‐
cusesonfieldchecks
forthe76‐RH190.
Whilemostofthe
fieldchecksdescribed
hereinalsoapplyto
the75and771,we
don’tfocusonthose
instrumentsspecifi‐
cally.
DON’TSWEATTHEDETAILSIFIT’SNOTNECESSARY:
Wedescribeanumberoffieldchecksinthischapterwhichallowyou
todeterminewhetheryourtransitisintopoperatingcalibration.
Butgoodjudgmentcanbeatimesaver—ifyoudon’tneedtheulti‐
mateinaccuracyforaparticularjob,youcaneditorignorethese
fieldchecksaccordingly.Wepresentthemheretogiveyouacom‐
pletepictureofinstrumentfieldcalibration.