9
5.
Centering the instrument using the optical plummet
A)
Adjust the eyepiece so the bull's-eye
reticle comes into sharp focus.
B)
Adjust focus knob so ground target comes
into sharp focus.
C)
Slightly loosen the tripod fastening
screw and move the instrument until the
ground target is centered in the optical plummet.
D)
Tighten the tripod fastening
screw and recheck the level
vials by following steps 3 and 4 again.
2.2 Telescope Eyepiece Focus
Point the telescope toward a bright area and turn the telescope eyepiece until the
crosshairs come into sharp focus.
Avoid parallax, the shifting seen between the target and the crosshairs when your eye
moves while sighting through the telescope. Parallax will cause inaccurate measure-
ments.
To avoid parallax, perform the following:
1.
Focus the telescope on a target.
2.
You should be able to move your eye up and down or left and right without
seeing the target shift with respect to the crosshairs.
3.
If there is parallax, readjust the eyepiece.
Always remove any parallax before operation to assure accurate measurements.
