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|  MIL-T-46311B(MU)
4.6.4.2 Purging.- The optical assembly area of the telescope shall
be flushed with dry nitrogen gas to conform to the requirement of 3.4.3.
A dew point tester (commercially available standard equipment) shall be
attached to the telescope. Gas emerging from the scope hole in the
rotating head of the telescope shall be bled through the tester until it
conforms to the value specified in 3.4.3. The telescope shall then be
quickly sealed. Pressure of the gas remaining in the telescope shall be
brought up to 0.1 to 0.25 psi. Purging shall be conducted at a temperature
of +60F to +90F.
4.6.5 Cleanliness.- The assembled optical components shall be inspected
for dirt by viewing a uniformly illuminated field having a brightness of
300 20 apparent foot candles. Inspection for all other defects shall be
made by the technique of shadowing. All defects shall lie within the
limits specified in 3.5.
4.6.6 Orientation.- The telescope shall be mounted on Azimuth Test
Fixture, Drawing F7691596, by means of an adapter provided with appropriate
locating surfaces to receive and position the telescope in the fixture,
with the mounting surface, elbow assembly, indices, counters, and lead
knob oriented as prescribed in 3.6.
4.6.7 Collimation.
4.6.7.1 Collimation, pre-vibration. - The telescope shall be mounted
and set as in 4.6.6 with the line of sight, established by the intersection
of the reticle cross lines, in coincidence with a point on the target (or
collimator target reticle). Record the position of the telescope reticle
on the target. Record the azimuth position on the vernier scale of the
counter. These points or settings shall be within the tolerance specified
in 3.7.1.1.
4.6.7.2 Collimation, post vibration.- Subsequent to the vibration
test of 4.6.3, as required by 3.3.3, the telescope shall meet the require-
ments of 3.7.1.2 after the telescope has been remounted on the fixture
specified in 4.6.6. The line of sight shall not have changed by more than
the tolerance specified in 3.7.1.2.
4.6.7.3 Open sight.- The line of sight shall be set to zero elevation
(Horizontal). A wall target shall be utilized showing individual targets
that have been laid out, one for the line of sight through the telescope
optics and one for the line of sight through the open sight. The line of
sight through the open sight of the telescope shall be parallel in deflect-
ion to the optical line of sight within the tolerance specified in 3.7.1.3.
4.6.8 Image tilt.- The telescope shall be oriented in accordance with
4.6.6. Using an adjustable auxiliary telescope and a flat surface to
position the auxiliary telescope at the eyepiece of the telescope under
test, adjust the auxiliary telescope to the height of the telescope eye-
piece. Adjust the auxiliary telescope's vertical reticle line in coincidence
with a plumb line. Sight through the auxiliary telescope and the eyepiece
of the telescope to the target. The vertical target line image shall be
parallel to the vertical reticle line of the auxiliary telescope within the
tolerance specified in 3.7.2. The tolerance can be measured by rotating the
deflection (azimuth) knob and reading the error on the 3200 counter vernier
scale. The auxiliary telescope's vertical reticle line shall be used as an
index.
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