Brunson 771 - Reticle Projection

27 Operation and Adjustment Manual
encelinerequiresonlycollimation.Butsometimes,ifyouare try‐
ingtotransferaspecifichorizontalelevationoraverticalplane
fromonesideofanobjecttoanother,thetechniqueofcollineation
canprovidetheanswer.
Aswithmostoftheothertechniquesdiscussed,thecollineation
procedureissimply
abuck‐in.Tounderstandthedefinitionsofthe
nearandfartargetsinthisinstance,let’stakealookattheproce‐
dure.
1. Collimate.Asthefirststep,collimateyourtransittothe
referenceinstrument.

2. Bringfocalpointstoamiddledistance.Temporarily
insertapiece
ofpaperorotherverythinmaterial(ithelps
tohaveawhitenon‐reflectivesurface)aboutmidwaybe‐
tweenthetwoinstrumentsandfocusbothtelescopeson
thissurface.

3. Centeryourtransitonthe“near”target.Removethepa‐
perandlookthroughtheworkinginstrument—you
shouldbeabletoseethereticleimageofthereferencein‐
strument.Focuspreciselyonthisimage.We’lldefine
thisastheneartarget.Makelateraladjustmentsusing
yourcrossslideorprecisionliftasneededtobringthe
reticleofyourtransitintoalignmentwiththereference
instrument’sreticle.

4. Returnreferenceinstrumentfocustoinfinity.Focusthe
referenceinstrumentbackouttoinfinitywithamirror.

5. Centeryourtransitonthe“far”target.Focusthework‐
inginstrumentatinfinityandfindthereferenceinstru‐
ment’sreticleimage.Thisisdefinedasthefartarget.
Makeangularadjustments
onyourtransit(horizontal
andverticaltangentadjustmentscrews)asneededto
alignthereticleimages.

6. Repeatsteps2through5untilbucked‐in.Whenyour
transitcanbefocusedonboththenearandfartargets
withoutmakingfurtheradjustments,youhaveaccom‐
plishedcollineation.Thetwoinstrumentsnolongersim‐
plyhaveparallellinesofsight,buthavebeenadjusted
ontopreciselythesamelineofsight.
Wehavealreadydiscussedthefactthatatelescopemaybeused
“backwards”(see“Collimation”inthissection).Accordingly,your
Asalways,whenfocused
onthefartarget,onlythe
transit’sangularcontrols
producevisibleresults.For
settingtotheneartarget,
makelateralshiftsusinga
cross‐slideorprecisionlift.
ReticleProjection