MIL-DTL-48558C
3.5.5 Vibration "B". The telescope, mounted to the test equipment using its
standard attachment mechanism, shall be vibrated in the vertical plane shown in Figure 1
for a total of 15 ± 1 minutes of sweep cycle vibration. A complete sweep-cycle shall
consist of vibration from origin (5 Hz at 1 inch double amplitude) to mid-point (5 ± 0.5 g s
at 500 Hz) to origin, and shall have a duration of 15 ± 1 minutes. Double amplitude shall
be constant at 1 inch between 5 Hz and 10 Hz and varied with frequency to maintain a
constant 5 ± 0.5 g s acceleration between 10 Hz and 500 Hz. Upon completion of
vibration, the latch and cam lock used for attachment shall not have loosened, the telescope
shall exhibit no evidence of damage or physical failure, and it shall meet the requirements
of 3.6 through 3.13 inclusive. (See 6.6)
3.6 Collimation change, post shock and vibration. The line of sight established in
3.4.1 prior to the shock or vibration test shall not deviate more than .25 mil in azimuth or
.25 mil in elevation due to subjecting the telescope to Vibration "A", Vibration "B", or
Shock.
3.7 Sealing. The elbow telescope unit shall be capable of holding dry nitrogen at a
minimum internal pressure of 5 psig for a period of 1 hour ± 5 minutes without the loss of
pressure in excess of 0.2 psi for that 1 hour period.
3.8 Purging. The interior of the telescope shall be purged with dry nitrogen
supplied at a pressure of 6.00 ± 0.25 psig until the dew point of the emergent gas is no
higher than -25 °F. Purging apparatus shall be removed when the relief valve is reseated
and maintains a pressure of 3.0 ± 0.1 psig.
3.9 Optical.
3.9.1 Parallax. The parallax at the center cross of the reticle pattern shall not
exceed 0.25 mil when viewing targets between 125 meters and infinity.
3.9.2 Reticle accuracy. The angular separation between the 0 mil and the 60 mil
graduations shall be 60 ± 0.50 mils.
3.9.3 Parallelism of reticle and image. With the telescope oriented as stated in 3.4,
the 20 mil horizontal line of the telescope reticle shall be parallel to the image of a leveled
horizontal line within 30 minutes of arc.
3.9.4 Resolution. The resolution of the optical axis shall be 5 seconds of arc or less
when using an observation telescope of at least 3 power and an entrance pupil of at least
0.4 inches. Resolution consists of detectable line structure and proper line count in all four
meridians. Total spread in focus shift between meridians shall not exceed ½ diopter as
measured at the eyepiece.
3.9.5 Cleanliness. The optical system shall meet the cleanliness requirements of
MIL-PRF-13830 and there shall be no more than 3 particles of dirt visible on the reticle
and the area of such particle shall not be in excess of the area equivalent to a size 10 dig.
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