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|  MIL-T-50760(MU)
4.6.4 Cleanliness. - The optical surfaces of the telescope shall be
inspected for cleanliness in accordance with MIL-O-13830. Inspection for
dirt particles shall be made through the eyepiece by viewing a uniformly
illuminated field having a brightness of approximately 300 foot candles.
All dirt size evaluations shall take into account the viewing magnifica-
tion. Inspection far condensates shall be made with the unaided eye view-
ing through the objective and eyepiece ends of the telescope by the shadow-
ing technique. Cleanliness shall conform to the requirements of 3.5.4.
4.6.5 Resolution. - Position the telescope on a holding device capable
of accepting the exterior mounting surface of the objective tube of the
telescope. Perform this test utilizing an observation telescope with a
magnification of at least 3 power (3X) and a resolving power chart on a
wall target. The test methods and procedures shall be in compliance with
the "Resolution Test" specified in MIL-O-13830 and the resolving power
chart shall contain 4 line sets as shown in Figure 1 therein. The focus
of the observation telescope shall be established at one best focus sett-
ing for viewing of the detectable line structure and proper line count of
the resolution target. Resolution of the telescope optical system shall
meet the requirements specified in 3.6.3.
4.6.6 Accuracy. - Perform the following tests with the telescope posi-
tioned on special testing equipment conforming to 4.5.2.3.l.
4.6.6.1 Collimation. - Position the telescope with the eyepiece in a
vertical position. Observe through the eyepiece of the telescope. The
intersectingpoint of the telescope reticle centerlines shall be in co-
incidence with respect to the intersecting point of the target reticle
lines within the tolerance specified in 3.6.1 as measured on the 0.50 mil
diameter circle of the target reticle. Repeat the collimation test pro-
o
cedure above shen the telescope is rotated 90 to the left and 90 to the
right of the original test position. The intersecting point of the tele-
scope reticle shall be within the 0.50 mil diameter circle of the target
reticle at both positions to insure overall compliance with 3.6.1.
4.6.6.2 Parallax. - Parallax requirements shall be met when the tar-
get image is adjusted as specified in 3,6.2. Parallax will be recognized
by any apparent displacement of the telescope reticle lines with respect
to the center target image lines when the observer's head is moved from
side to side or up and down. Patallax shall be measured at the optical
axis (center of the reticle pattern). Displacement between the telescope
reticle and target image shall not exceed the tolerance specified in 3.6.2.
4.6.6.3 Parallelism of reticle and image. - Perform this test in con-
junction with the test in 4.6.6.1 when each of the indices as specified in
3.6.4 are in position and coincident with respect to the index of the "V"
block. One extremity of the telescope vertical reticle shall be coincident
to the vertical target image line. The reticle line shall be parallel to
the target image line within the tolerance specified in 3.6.4, as measured
at the other extremity of the telescope reticle line with respect to the
target image tolerance marks.
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