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|  MIL-T-45688D(MU)
3.5.3 Vibration.- The telescope shall show no evidence of physical
failure due to being vibrated successively along three (3) mutually
perpendicular axes. Vibration shall be a simple harmonic motion, the
frequency varying either linearly or logarithmically from 5 to 55 to
5 CPS in five minute cycles for a total of 15 minutes along each of the
axes. The amplitude of vibration shall be maintained constant at 1/64
inch (1/32 inch total excursion). Following the vibration test the
telescope shall meet all subsequent requirements.
3.6 Sealing.- The telescope shall show no evidence of leakage in
excess of 0.2 pounds per square inch gage when subjected to an internal
pressure of 5 0.10 pound per square inch (psig) for a minimum of 2 hours.
The interior atmosphere of the accepted telescope shall contain nitrogen
having a dew point at least as low as -25F.
3.7 Cleanliness.
3.7.1 Dirt.- Inspection for dirt and foreign particles (classed as
dirt) shall be made from the eye end only. The maximum size of any visi-
ble particle, when the reticle is brought into sharp focus, shall be a re-
ticle line width. The maximum number of dirt particles appearing within a
central field of view of 50 mils diameter shall be four (4). The maximum
number of dirt particles appearing outside this field of view shall be
five (5). The minimum angular separation between dirt particles shall
be 15 mils. Dirt particles smaller than reticle line width shall be
ignored regardless of distribution.
3.7.2 Other defects.- There shall be no evidence of moisture,
grease, fingerprints, condensates, fractures, and adhesive separations
when viewing thru the objective and eye end of the instrument.
3.8 Accuracy.
3.8.1 Orientation.- The telescope shall meet the requirements of
3.8.2 to 3.8.3 inclusive while positioned as follows:
a. The geometric axis of the objective tube, as determined by
the spherical surfaces of the mounting ring adjacent to Window Assembly
and the mounting ring adjacent to the articulated joint, shall be in a
horizontal plane.
b. The locating pin shall be set 30 degrees, plus or minus
one minute counter-clockwise from the horizontal as viewed from the
eyepiece.
c. The eyepiece shall form an angle of 20 15' below the
geometric axis of the objective tube when measured on the hanger bracket
flat surface at the eyepiece end.
3.8.2 Collimation.
3
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