Section II. EQUIPMENT DESCRIPTION AND DATA
1-8. EQUIPMENT CHARACTERISTICS, CAPABILITIES, AND FEATURES.
a. M115 Panoramic Telescope. The M115 telescope is a hermetically sealed unit used with the M137 telescope
mount on the M 11 OA2 self-propelled howitzer. It is a 4-power, 10-degree field of view instrument with analog counters.
Counters and reticle are illuminated by LEDs. The telescope consists of three main assemblies: the rotating head, the
body assembly, and the elbow assembly. The rotating head contains the entrance window and serves to house the 90-
degree prism. The body assembly contains two objective lenses, reticle, deflection knob, and adapter assembly. The
elbow assembly has a total excursion of 30 degrees and contains a penta prism, pechan prism assembly, cell assembly
(erector), eyepiece assembly, and assembled gearing.
b. M138 Telescope Mount. The M138 telescope mount adapts the M139 elbow telescope to the M110 A2 self-
propelled howitzer. The mount provides adjustments in elevation and deflection (azimuth) for direct fire with the 8-inch
c. M137 Telescope Mount. The M137 telescope mount adapts the M115 panoramic telescope to the M11 OA2
self-propelled howitzer. The mount provides adjustments in elevation and cant (cross-level) for indirect fire. The M137
telescope mount consists of two subassemblies, one mounted on top of the other, and secured by four screws. The upper
subassembly contains most of the electrical system and the mounting surface for the telescope. The lower subassembly
consists of a mounting bracket, elevation knob and elevation counter, correction knob and counter, and cross-level knob.
d. M139 Telescope Elbow. The M139 elbow telescope is a 3-power, 13-degree, 20-minute field of view
instrument. The reticle, illuminated by the M36 instrument light, is used for direct fire and is graduated in meters for range.