Install guide

ARMY TM 5-6675-308-34
MARINE CORPS TM 08837A-34/2
(1)
(2)
(3)
(4)
(5)
Grasp the carrying strap with both hands just
above the two clamping levers and pull out-
ward to release the clamping levers from the
base assembly.
Lift the dome-shaped cover directly off the
instrument and lay it to one side,
Release the three clamps which secure the
theodolite to the case base. Grasp the theodo-
lite by the standard that has the trademark
inscribed on it and lift the theodolite off the
base.
Attach the instrument to the tripod head by
screwing the fixing screw snugly into the base
of the tribrach.
Replace the cover on the base of the case to
prevent dust and moisture from entering the
case.
c. plumbing and Leveling the Theodolite. The pro-
ocedure. for plumbing and l eveling the theodolite is as
follows:
(1) Loosen the fixing screw slightly and carefully
move the instrument around on the head of
the tripod until the point of the plumb bob is
centered exactly over the station.
Tighten the instrument to the tripod head,
making sure that the point of the plumb bob
remains centered over the station.
Excessive tightening of the fixing screw
will bend the slotted arm and damage the
tripod head.
(3)
(4)
5-6
Loosen the leveling screws to expose sufficient
thread (3/8 to 1/2 inch) on the three screws to
permit the instrument to be leveled. Rotate
the instrument until the axis of the tubular
level is parallel to any two of the three level-
ing screws. Center the bubble by using these
two leveling screws. Grasp the leveling screws
between the thumb and forefinger of each
hand and turn the screws simultaneously so
that the thumbs of both hands move either
toward each other or away from each other at
the same time. This movement tightens one
screw as it loosens the other. The bubble
always moves in the same direction as the left
thumb.
Rotate the instrument 1,600 roils; this places
one end of the plate level over the third
leveling screw. Using this screw, center the
bubble,
(5)
(6)
(7)
(8)
(9)
(10)
Return the instmment to the first position ((3)
above) and again center the bubble.
Return the instrument to the second position
((4) above) and again center the bubble.
Repeat (5) and (6) above until the bubble
remains centered in both positions,
Rotate the instrument 3,200 roils from the first
position. If the bubble remains centered in this
position,
rotate the instrument 3,200 roils
from the second position. If the bubble re-
mains centered in this position, rotate the
instrument throughout 6,400 roils. The bubble
should remain centered; if it does, the instru-
ment is level.
If the bubble is not centered when the instru-
ment is rotated 3,200 roils from the first posi-
tion ((8) above), the level vial is out of adjust-
ment. To compensate, move the bubble half-
way back to the center of the level vial, using
the same leveling screws that were used for
the first position. Rotate the instrument 3,200
roils from the second position and move the
bubble halfway back to the center of the level
vial, using the one remaining leveling screw.
The instrument is now level, and the bubble
will come to rest in its vial at the same off-
center position regardless of the direction in
which the instrument is pointed. The level vial
should be adjusted at the first opportunity.
After the instrument is leveled, check the
optical plumb to ensure that the instrument is
centered exactly over the station. If it is not,
center the instrument over the station by shift-
ing it on the tripod head, and again check the
level of the instrument. If necessary, repeat
the leveling process and again check the opti-
cal plumb. Repeat this process until the instru-
ment is level and centered over the station,
d. Focusing the Telescope to Eliminate Parallax.
Before a theodolite is used f
or measuring angles, the
telescope must be focused to eliminate parallax by
bringing the focus of the eyepiece and the focus of the
objective lens to the plane of the reticle (crosslines).
This is accomplished as follows: Point the telescope
toward the sky or a neutral background and rotate the
knurled ring on the telescope eyepiece until the reticle
crosslines are sharp, distinct lines. (In doing this, the
observer should be very careful to focus his eye on the
crosslines, not the sky). Next, point the telescope
toward a well-defined distant point and, still focusing
the eye on the crosslines, bring the point into a clear,
sharp image by rotating the knurled focusing ring on
the telescope. Use the horizontal tangent screw to
center the vertical crossline on the point. To check for
elimination of parallax, move the eye horizontally back
and forth across the eyepiece. If the parallax has been