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|  MIL-T-48554A(AR)
3.7.1 Collimation chanqe, - lost vibration. This requirement
shall be met with conditions of 3.7 re-established without
readjusting boresight subsequent to vibration. The line of sight
established prior to vibration shall not deviate more than .25 mil
in deflection due to subjecting the telescope to Vibration "A" or
Vibration "B".
3.8 Sealing and Purging.
3.8.1 Optical assembly area. The telescope optical assembly
area shall be capable of sustaining an internal pressure of 7 +
0.10 pound per square in gage (psig) for a minimum of one hour with
no evidence of leakage.
3.8.2 Counterbox area. The counterbox area of the telescope
shall be purged with dry nitrogen supplied at a pressure of 5 +
0.10 psig for a minimum of one hour with no evidence of leakage.
3.8.3 Purging. The optical assembly and counterbox area of
the telescope shall be purged with dry nitrogen supplied at a
pressure of 8 + 1/4 psig until the dew point of the emergent gas
is not higher than -25F. Purging apparatus shall be removed when
relief valve is reseated and maintains a minimum pressure of 5
psig.
3.9 Cleanliness.
3.9.1 Dirt. Inspection for dirt and foreign particles
(classed as dirt) shall be made from the eye end only. The
maximum size of any particle appearing on the reticle surface
shall not exceed the width of the reticle line. The maximum
number of dirt particles appearing within a central field of view
of 50 mils diameter shall be three (3). The maximum number of
dirt particles appearing outside this field of view shall be three
(3). The minimum angular separation between dirt particles shall
be 15 mils. Dirt particles smaller than 1/4 of the reticle line
width shall be ignored regardless of distribution.
3.9.2 Other defects. There shall be no evidence of
moisture, grease, fingerprints, condensates, fractures, and
adhesive separations when viewing through the objective and eye
end of the instrument.
3.10 Optical
characteristics.
3.10.1 Eyepiece focus. The best eyepiece focus of the
reticle image shall be fixed between the limits of -0.50 and
-1.00 diopters. The variation in eyepiece focus between the
horizontal and vertical image shall not exceed 0.25 diopter.
3.10.2 Parallax. Parallax at the center of the field shall
not exceed 0.15 mil when viewing a target at 80 + 10 meters.
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