188.8.131.52 Image wander.- This test can be performed concurrently with
the test specified above. The auxiliary telescope, positioned at the eye-
piece, shall contain a calibrated reticle capable of measuring reticle
image wander within the limits specified in 3.7.3. Sight through the
auxiliary telescope and note the position of the reticle image. Rotate
the head assembly through 2 complete revolutions and note the position
of the reticle image. The position of the image shall not have deviated
from the position first noted by more than the tolerance specified in 3.7.3.
This examination shall be repeated with the elbow positioned against the
right and left swing stops.
4.6.9 Parallelism of reticle and image.- This test can be performed
concurrently with the test specified in 4.6.8. The vertical reticle line
of the telescope shall not deviate from the image of the vertical target
line by more than the tolerance specified in 3.7.4. The vertical reticle
line of the auxiliary telescope shall again be used as the index to measure
the error in the telescope. This examination shall also be repeated with
the elbow positioned against the right and left swing stops through at
least one full revolution of the telescope head in azimuth.
4.6.10 Eyepiece focus.- The telescope eyepiece is a fixed focus
assembly and it shall be set between the tolerances specified in 3.7.5.
To determine the correct setting of the eyepiece, a dioptometer of three
power (3X) shall be used that has been adjusted to the individual eye.
This can be accomplished by sighting through the dioptometer at a white
background and adjusting the eyepiece of the dioptometer until the reticle
is at the sharpest point obtainable. Position the barrel of thr dioptometer
to set the index at zero. When this has been accoplished, sight through
the dioptometer and the eyepiece of the telescope. Observe the reticle
of the telescope, and compare it with the reticle of the dioptometer.
Adjust the barrel of the dioptometer to make the reticle of the telescope
go out of focus; then re-adjust the barrel to bring the telescope reticle
into focus at the sharpest point. Read the error on the scale on the
barrel of the dioptometer. Several repeat readings in both directions
should be made to determine conformance to requirements.
4.6.11 Parallax.- Parallax shall be determined by viewing a target
at the distance specified in 3.7.6. Parallax can be distinguished by
adjusting the vertical and horizontal lines of the telescope reticle
parallel to the image of the target lines without touching, leaving a
minimum of space or light between the lines. The observer shall move
his head from side to side or up and down. Any movement of the target
in either direction (the space getting wider or narrower) is considered
parallax. The amount of parallax observed shall not exceed the tolerance
requirements of 3.7.6.
4.6.12 Resolution.- This test shall be performed in accordance with
the resolution test specified in MIL-O-13830. The telescope shall permit
resolution of a target within the limit specified in 3.7.7.
4.6.13 Reticle.- The test for reticle graduation accuracy shall be
conducted in accordance with the reticle requirements in MIL-O-13830 to
determine conformance with the requirements of 3.7.8.