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| MIL-T-81333A(OS)
3.3.2 Image quality and definition. When subjected to a star test as specified herein, the image shall appear
round with a sharply defined edge The image shall be free from points flare, rays, fog, haze or halos other than
the normal diffraction rings. No difference in coloration between one side of the star and the other shall be seen
A slightly defocused image" shall remain round The ocular setting between the three stars shall not exceed 0.2 diopter.
3.3.3 Resolution. The limit of resolution at any point within 1 degree of true field from the field center shall
be 6 seconds or batter for a magnification of 10 diameters and 10 seconds or better for a magnification of 6 di-
ameters for parallel lines of any orientation.
3.3.4 Reticle A reticle shall be provided for use at either magnification and shall be mounted in the right opti-
cal system of the telescope The reticle pattern at either magnification shall consist of two centrally located concen-
tric circles. The dimensions of the reticle pattern will be specified by the contracting activity (see 6.2.1). The lines
shall be clean-cut, unbroken, and filled with suitable hard, durable and opaque material. The rightoptical system
containing the reticle shall be free from parallax on a distant target.There shall be a nameplate, mounted in a
conspicuous location on the telescope. which will give the diameter of each of the circles of the reticle pattern
in true field at 6 and also at 10 diameters magnification.
3.3.4.1 Reticle illumination. Artificial illumination shall be provided for the reticle Such illumination shall be
bymeans of a Mazda,64" 6 to 8 volt 3 candle power lamp with contact base and spherical bulb 3/4 inch
in diameter. A Lamp Socket Mark 9, as listed on LD16792Q for this lamp will be provided by the contracting activity,
but the contractor shal supply the holder for this socket Illumination shall provide substantially uniform illumina-
tion of both circles of the reticle at either magnification. Furtermore, no bright and troublesome reflections shall
be visible in the field of view nor at a distance in the dark.
3.35 Reflection reducing films- The air-toglass surfaces of each element of the optical system of the tele-
scope, excluding both surfaces of teh reticle plate, or glass surfaces lying in a foclal plane,shall be treated with
a reflection-redudng film in accordance with MIL-C-675.
3.3.6 Stray light. No stray or scattered light, or reflections from surfaces within the telescope shall be visible
in the field of view, or enter the exit pupil, or be visible in the vicinity of the exit pupil when the pupil is viewed
from a distance of 2 0r 3 feet along the Ocular axis extended. All internal surfaces from whichstray or scattered
light might be reflected shall be threaded, knurled, grooved or scored in such manner as to avoid such reflection.
Such surfaces, and any other surfaces from which troublesome reflection might occur, shall be darkened by treat-
ment. No paint, enamel, lacquer, or other material which might become detached from the surface to which ap-
plied, shall be used in the interior of these telescopes.
3.3.7 Collimation.
3.3.7.1 Parallelism. When two parallel pencils or bundles of light rays are projected into the two objective lenses
respectively, the conjugate rays emerging from the two eyepieces shall be parallel within the following limits for
any setting of the interocular distance scale:
a. Fourteen minutes of arc (equivalent to 1.4 minutes of true field at 10x and 2.3 minutes at 6x) in the
direction perpendicular to the plane determined by the two eyepiece axes.
b. Twenty-eight minutes of arc (equivalent to 2.8 minutes of true field at 10x and 4.6 minutes at 6x) diver-
gence and fourteen minutes of arc (equivalent to 1.4 minutes of true fieid at 10x and 2.3 minutes at 6x)
convergence in a direction parallel to the plane of the two eyepiece axes.
3.3.7.2 Squaring. The images of a straight tine formed by the two optical systems, at either magnification, shall
be parallel within one-half degree.
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