CHAPTER 5 - REPRESENTATIVE FIRE CONTROL INSTRUMENTS Section I 86. GENERAL. a. Telescope is the standard nomenclature designation for instruments of a number of different types. Some of the representative types of telescopes illustrated and described in this section are used for observation; others are employed to aim weapons. Of these, the Telescope M6, Telescope M1, and Telescope M70 are of the straight tube type; the Observation Telescope M48 and Telescope M31 are of the prism-offset type; and the Telescope M60 is of the periscopic type. 87. TELESCOPE M6 (ANTITANK). a. The Telescope M6 (fig. 114) is a straight tube telescope with no magnification. With the Telescope Mount M19, it comprises the on-carriage sighting equipment for an antitank gun. This instrument has a lens erecting system and a symmetrical eyepiece. This eyepiece provides a large exit pupil (0.6 in.) and large eye relief (over 4 in.). The large eye relief is provided to avoid contact between the eye of the gunner and the eyepiece when the gun recoils. The field of view is 11 degrees. b. The telescope reticle (fig. 101g) is graduated for various leads and ranges. To aim the gun, the elevating and traversing mechanisms on the weapon are operated and the target is viewed through the reticle until the dot on the reticle which indicates the proper lead and range is imposed on the target. The reticle is illuminated through a window by an electric lamp, retained by and a part of the mount. 88. OBSERVATION TELESCOPE M48 (OBSERVATION POSTS). 8. The chief purpose of the Observation Telescope M48 (fig. 115) is to assist in the observing of artillery fire. The instrument has a large achromatic objective and an orthoscopic eyepiece. The image is erected by a Porro prism system which gives the instrument its characteristic "offset." There are diaphragms between the objective and the erecting system and between the erecting system and the eyepiece. There is no reticle. b. This instrument is a 19.6-power telescope having a field of view of 2 degrees 8 minutes and an exit pupil of 0.1-inch diameter. To provide the steadiness required in the use of a high-powered instrument, the telescope is strapped into a cradle mounted on a |