Topcon AT-G4 - Collimation of the Instrument

screws.
(2) Revolve
the telescope 180° around its vertical axis.
If the bubble remains centered, adjustment is not
required.
If the bubble moves from the cen t er, however, adjust·
ment must be made, as follows .
..
(3) Tighten the circular level adjustment screw on the side
that the bubble has moved to, with the accessory adjust·
ing wrench . This will return the bubble towards the
center. However, return the bubble by only one-half
the a mount of er ror, by t his method.
(4) Re·center the circul ar level butlble with the three level·
ing screws.
(5) The bubble shou ld now remain centered, as the tele·
scope is revolved around its axis.
If not, however, repeat the adjustments noted above
until the bubble remains centered when the instrument
is revolved on its axis.
Circular
level --- --
Adjustment
screw
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Collimation of the Instrument
(1) Set the instrument up on a tripod at a po i nt midway
between two walls, which are approximately 50 meters
apart.
(2) Level the instrument properly, by centering the bubble
of the circular level with the three leveling screws.
(3) Place identical scales against both walls and alternately
collim ate both scales on a horizontal line of sight, using,
the same number on both scales for this purpose. Thus,
if necessary, adjust the scales up or down, fo r alignment
to the same scale division or figure.
(4) Move the instrument to a posit ion about 2 or 3 meters
from one of the scales and center the level bubble once
more, with three leveling scre\NS.
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