MIL-P-45651B(MU)
point to a sharply defined target located at
lines of sight shall not deviate beyond the
the specified distance from the periscope
tolerance specified in 3.8.1.1 and 3.8.1.2.
window. Parallax will be recognized as any
4.5.7.2 Plumb travel. This test shall be
apparent movement of a reticle in relation
performed with the aid of an auxiliary tele-
to' the target image when the observer's
scope containing a vertical reticle line.
head is moved from side to side or up and
Position the input coupling to 67 degrees
down. Parallax at the boresight point with
and 30 minutes. The verticle reticle line of the
respect to the target image shall not exceed
auxiliary telescope shall be adjusted parallel
the tolerance specified in 3.6. Note: 0.1 mil-
to the image of a calibrated plumb line tar-
Thickness of a reticle line.
get. The line of sight (8 power system) shall
not deviate more than the tolerance specified
4.5.5 Torque, parallax adjustment screws.
in 3.8.2 when the coupling is rotated through
The torque required to rotate the parallax
the excursion indicated..
adjustment screw through the range of ob-
jective travel shall be measured with stand-
4.5.7.3 Elevation accuracy. This test shall
ard measuring equipment affixed to the
be performed with the aid of an auxiliary
adjustment screw. The measured torque shall
telescope containing a horizontal reticle line.
not exceed the value specified in 3.6.1 for
Direct a line of sight through the 8 power
the temperature indicated.
system of the head assembly to a calibrated
4.5.6 Sealing. The head assembly and body
target appropriate for measuring elevation
assembly shall be pressurized to the psig
accuracy of the line of sight. Any measured
value specified in 3.7. During the time period
change in the angular position of the input
indicated, the interior pressure shall not
coupling shall cause the same measured
decrease in excess of the tolerance specified
change in the line of sight within the toler-
when checked by suitable measuring equip-
ance specified in 8.8.3. Elevation accuracy
ment. Upon satisfactory completion of the
shall be measured at a minimum of four
sealing tests, the assemblies shall be flushed
positions in elevation and three positions in
with dry nitrogen. The flushing shall con-
depression starting with the line of sight
tinue until the gas bled from the assemblies
horizontal. One of these positions shall be
has a dew-point at least as low as --25° F.
at 22 degrees elevation and another at 18
at the pressure specified. The assemblies
degrees depression.
shall then be sealed. This is a post environ-
4.5.7.4 Backlash. This test shall be per-
mental test that shall be performed at +60°
formed utilizing the target specified in
to 90° F.
4.5.7.3. With the backlash excluded for di-
4.5.7 Head assembly. The following tests
rection of travel, record position of the input
shall be conducted with the head assembly
coupling and line of sight. Increase or de-
secured in special testing equipment that
crease the angular position of the coupling
shall position the datum planes X and Y,
approximately 10 degrees; then, With the
and side Y of the input coupling, as specified
backlash included, return the coupling to the
in 3.8. The equipment shall be capable of
recorded position without overtravel and
positioning the input coupling to any
record position of the line of sight. The dif-
measured angular position throughout its
ference between the two recorded positions
entire excursion.
of the line of sight is the amount of back-
lash. Backlash shall not exceed the tolerance
4.5.7.1 Collimation, eight power and unity
specified in 3.8.3.1.
power system. This test shall be performed
4.5.7.5 Coupling travel. The excursion of
with special test equipment that shall
measure any error in the reflected lines of
the input coupling shall be tested manually,
sight when the incident lines of sight are
and shall meet the requirements specified
established as specified in 3.8.1. The reflected
in 3.8.4.
8
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