Install guide

ARMY TM 5-6675-308-34
MARINE CORPS TM 08837A-34/2
b.
c.
Test. To test the optical plumb, suspend the
plumb bob from the leveled instrument and
mark a point on the ground exactly under the
point of the plumb bob. Remove the plumb bob
from the instrument and check to insure that the
instrument is accurately leveled (i.e., the vertical
axis is truly vertical). Look into the eyepiece of
the optical plumb. If it is in correct adjustment,
the mark on the ground will be centered in the
reticle.
Adjustment. If the point on the ground is not
centered
in the optical plumb reticle, center the
point by means of the three capstan adjusting
screws located near the optical plumb eyepiece.
Two of these adjusting screws are located on
opposite sides of the eyepiece, and the third
adjusting screw is located below the eyepiece
opposite a sprint-loaded plunger. The bottom
adjusting screw is locked in place by a capstan
retaining nut, which is located immediately
above the head of the adjusting screw. With an
adjusting pin, loosen the retaining nut and raise
or lower the reticle by turning the bottom ad-
justing screw to move the reticle image along
the axis of the optical plumb in the same direc-
tion that the screw travels. The two side adjust-
ing screws are used to move the image of the
reticle in the opposite direction from their
travel. If it is necessary to use these screws, they
should be rotated an equal amount in opposite
directions, It is usually necessary to loosen the
screw below the eyepiece slightly to adjust the
screws on the side and vice versa. To make the
adjustment, loosen one of the two opposed
screws and the retaining nut slightly. The spring-
opposed adjusting screw should be used for nec-
essary adjustments, and the opposed adjusting
screws should be used to complete these adjust-
ments. When the adjustment is complete, the
two opposed adjusting screws must be faily tight.
Lock the bottom adjusting screw in place by
tightening the retaining nut.
5-17. Verticality Adjustment.
a. Purpose. The purpose of the verticality adjust-
ment is to make the vertical crossline of the
reticle lie in a plane perpendicular to the hori-
zontal axis of the telescope.
b. Test. To test the verticality of the vertical
crossline, select a well-defined distant point as
near as possible to the horizontal plane of the
instrument and center the vertical crossline on
the selected point. With the vertical tangent
screw, elevate and depress the telescope. If the
vertical crossline continuously bisects the point,
the adjustment is correct.
c. Adjustment. There are three adjusting screws on
the telescope, a horizontal screw on the left side
and two slant screws on the right side. If the
vertical line does not continuously bisect the
sighted point, turn the two slant screws an equal
amount in opposite directions to rotate the reti-
cle until the vertical crossline does bisect the
point throughout the elevation and depression of
the telescope.
5-18. Horizontal Collimation Adjustment.
a.
b.
c.
Purpose. The purpose of the horizontal collima-
tion adjusting is to make the line of sight
perpendicular to the horizontal axis of the tele-
scope.
Test. To test the horizontal collimation, select a
well-defined point at least 100 meters from the
instrument and at approximately the same rela-
tive height. With the telescope in the direct
position, center the vertical crossline on the
selected point. Set the horizontal circle to any
reading less than 3,200 mils, close the cover on
the circle-setting knob, and record the reading.
Plunge the telescope to the reverse position and
take a second reading on the same point. The
instrument operator should repeat both readings
to insure that no error was made in reading the
instrument. These two readings should differ by
3,200 mils. Assuming no error in the pointings or
readings, any discrepancy between actual differ-
ence in the two readings and 3,200 mils is the
apparent error, or twice the horizontal collima-
tion error. If this discrepancy exceeds plus or
minus 0.100 mil (20”), the horizontal collimation
adjustment should be performed.
Adjustment. For the purpose of illustration as-
sume that the horizontal circle reading in the
direct position is 0000.200 mil and in the reverse
position is 3,200.800 mils. With the telescope in
the direct position, use the coincidence knob to
set the mean value (0.500) on the micrometer
scale. Using the horizontal tangent screw, bring
the main scale into coincidence with a value of 0
mil on the scale. In doing this, the vertical
crossline is moved off the point by the amount of
the horizontal collimation error. The vertical
crossline is then aligned on the selected point by
lateral movement of the reticle within the tele-
scope. To move the reticle, loosen (tighten) the
two adjusting screws in the slant position on the
right side of the telescope equally, and tighten
(loosen) the single adiusting screw on the left
side of the telescope. For moving the reticle, the
adjusting screw(s) should be loosened before the
screw(s) on the opposite side of the telescope is
tightened. Repeat the test and adjustment proce-
dure until the difference between the direct and
5-12