Representative Fire Control Instruments

ated in mils in the form of a cross with each arm being graduated from 5 to 50 mils. The reticle is lighted by an electric lamp. The eyepiece assembly may be focused to accommodate the eye. The diopter scale, graduated from plus 3 to minus 3 diopters, permits prefocusing. Two internal filters, one amber and one blue, are provided in the telescope. Each is controlled by a lever extending outside the housing.

e. Elbow Telescope M35. The objective, penta prism, reticle, reticle lens, and filter assembly of the Elbow Telescope M35 are identical with those of Telescope M3. The same provision is made to focus the eyepiece to accommodate the eye. The three-element eyepiece consists of a compound eyelens, equi-convex center lens, and compound field lens. The magnification may be varied between 10 and 20 power by rotation of the knurled focusing sleeve which changes the positions of the erectors of the lens erecting system with relation to each other and with the reticle lens and the eyepiece diaphragm. In all positions, the erectors are over 2 inches apart. The focusing sleeve mechanism contains a cam tube which is attached to the focusing sleeve. The cam tube has two helical slots of different pitch. Shoes attached to the erector lens cells ride in these slots and cause the erector cells to slide backward and forward when the focusing sleeve is rotated. The magnification secured at any setting is indicated by the marking on the focusing sleeve.

f. The telescope body has two bearing surfaces along the eyepiece leg of the telescope for clamping to the mount. These straddle the portion of the body holding the penta prism. A pocket extending from the telescope body is filled with lead to counteract the unbalance of the objective legs of the two elbow telescopes. A leather objective cap attached to the sunshade protects the objective when the telescope is not in use.

Section III

PANORAMIC TELESCOPES

97.

GENERAL.

a. The panoramic telescope is a type of fire control instrument employed to aim a gun or howitzer in azimuth. It is used in conjunction with a telescope mount to which it is assembled. The telescope mount travels in azimuth with the weapon, carrying the line of sight of the telescope, The telescope provides the mechanism for setting the azimuth angle while the mount or other associated equipment supplies the elevation, angle of site (vertical angle), and cross-leveling mechanism.

b. The characteristic feature of the panoramic telescope is that it raises the line of sight and maintains an upright image regardless of

Representative Fire Control Instruments

whether the line of sight is directed forward, to the side, or to the rear of the observer. The upper or rotating head of the instrument and the line of sight may be rotated 360 degrees or through any desired angle in the horizontal plane without requiring the observer to change his position. The mount provides for the raising or lowering of the line of sight to any required angle. By the combination of these motions, the line of sight can be directed on any aiming point. The different types and models of panoramic telescopes are of the same basic design. They differ in the components of their optical systems, the angle at which the eyepiece is mounted with relation to the upright body of the instrument, the indexing of the scales, provisions for setting in deflections, method of mounting, reticle patterns, manner of adjustment, lighting, and other details. A number of these differences are determined by the characteristics of the materiel with which the instrument is used.

C.

d. An objective prism, a rotating prism, and an Amici prism (fig. 124) comprise the erecting system of the great majority of panoramic telescopes. An erecting prism assembly (fig. 126) may be used in place of the rotating prism.

98. PANORAMIC TELESCOPE M12 (FIELD ARTILLERY).

a. The Panoramic Telescope M12 (fig. 124) is one of the most modern adaptations of the conventional design. It has a magnification of 4 power and a field of view of 10 degrees. It is used on a telescope mount primarily to point a gun or howitzer in azimuth for indirect fire and may also be used for direct fire.

b. The erecting system is comprised of an objective prism, rotating prism, and Amici prism (figs. 88 and 99). A plane glass window in the rotating head protects the optical system from dirt, dust, and other foreign matter; it particularly protects the objective prism from scratches and breakage. A compound objective is mounted between the rotating prism and the Amici prism. The eyepiece is of the Kellner type with an achromatized doublet field lens and an equiconvex eyelens. A reticle with appropriate pattern for the type of materiel used is mounted in the focal plane of the objective between the Amici prism and the eyepiece. The model designation of the telescope indicates the reticle pattern. The reticle is illuminated by a lighting system for night use. An open sight on the side of the rotating head enables the observer speedily to pick up the designated target.

99. PANORAMIC TELESCOPE M1 (FIELD ARTILLERY).

a. A distinguishing feature of the Panoramic Telescope M1 (fig. 125) is that the eyepiece leg of the instrument slants upward at an angle of 25 degrees, permitting the observer to look downward at this angle and yet maintain a true horizontal line of sight.