Schneider battery telescope
The 75mm quick-firing field guns M. 194 were equipped with a Schneider battery telescope composed by the telescope, the goniometer, and the tripod.
The telescope (1) is of the same type as that adopted by the French artillery. It is inserted and fixed in the socket (2), in which, if necessary, it can be rotated around its axis. Its magnification is 17.5 times; its field of view is 3° 20’, which equates to 58 m at a distance of 1000 m.
In its ocular is visible:
a) a horizontal scale in a millièmes, to measure the angular positions, the divisions of the scale being numbered every 10 divisions, with zero in the middle;
b) two horizontal dashes, whose vertical standing is equal to the normal height of the burst, at 3/1000;
c) a vertical line which passing through the axis of the telescope, used to aim in direction.
The telescope can be rotated in its socket until the horizontal scale took a vertical position, to measure the angle of sight. The socket is connected by a hinge to the movable drum (3) of the goniometer; there is a level (3) on it, to position the telescope horizontally. In order for the socket to be springy, there is a slot along its outlet; once the telescope is inserted into the socket, the latter is fixed with a flat head screw (25).
The goniometer of the telescope has the same device as the gun goniometric sight and consists of two parts : a movable dial plate (9) and a fixed base (4). The fixed base is inserted into a tube (5), in which the clamping ring (6) is fixed by means of a butterfly nut (7), which, according to demand, either holds the base stationary or allows it to rotate in the tube (5). Along its circumference, the base is divided into 64 equal parts, and the cam gear (8) is fixed on its upper part. The scale of the base is made in the same way as the scale of the dial plate of the gun goniometric sight, the unit of measure of the angles and the numbering are the same.
The dial plate (9) is wedged in the base, from the socket of which it cannot come out, because the screw (10) does not allow it. In the dial plate is the lead screw (11), which is inserted in the teeth of the cam gear (8) of the fixed base, and which has a handle (12) at one end. A drum with two indicators (13) is fixed to the handle, and moves in front of a scale divided into 100 equal parts, drawn on one half of the dial (14). One of the two markers is hidden by a cover.
The rear end of the stem of the lead screw, which is spherical, is placed in a spherical socket (16), and its front end is placed in a ring, which can move slightly sideways. This device is designed to eliminate the gap that would form after time due to friction in the screw : by means of the pressure exerted by a spring (17) the screw rests constantly on the toothed wheel.
The dial plate has a line with a spherical level, which serves as indicator to calculate the divisions of the base. The upper end of the dial plate ends with a fork (30), in which the nut of the coupling (2) is placed; through the fork and the nut passes the stem (28) around which the coupling moves together with the optical tube.
On the left end of the stem, there is an indicator, which can be fixed to the stem, or move independently of it. It moves on a small scale (29), which allows the angles of sight to be measured to a magnitude that the telescope is not able to determine. This scale extends 200 millièmes or about 11° 30’ to the left and to the right.
The lower end of the base is wound in a small box, which ends with a sphere (18), serving as the axis of rotation of the goniometer and which is covered by two jaws (19). The jaws can be brought closer or further away, by means of a butterfly nut (20), to make the entire goniometer immobile, or allow it to occupy the desired position. The sphere rests on a support (21) threaded into the head (22) of the tripod.
The tripod consists of two parts : the head (22) and the legs (23). The support (21) is inserted into the upper part of the head (22), and its lower end ends in sockets, in which the upper ends of the three legs are placed.
The legs (23) are each composed of three brass tubes that fit into each other. Their cross section is triangular. The legs are placed with their upper end in the sockets of the head, in which they can move, each around its own axis, independently of each other. In their opposite end there is with a steel blade (31), with which they are driven into the ground.
Use of the battery telescope
To place the battery telescope, open the legs, pull their three tubes to extend them, place the tripod on the ground and fix the legs by driving their steel blade into the ground. Place the goniometer and then the optical tube in the coupling, inserting it with the objective forward and, loosening and tightening the screw (25). Place the stem of the goniometer vertically, loosening the jaws, with the help of the butterfly nut (20), and move the goniometer around the sphere (18) until the bubble of the spherical level stands exactly in the middle. Clamping the butterfly nut (20), the goniometer becomes completely stationary in a given position.
To carry the battery telescope, first separate the optical tube and the goniometer from the tripod. To separate and withdraw the optical tube, first loosen the screw (25) and pull the tube out of the coupling, and to remove the goniometer, loosen the butterfly nut (7). The legs are folded up and the tripod disassembled is placed in a leather case. The optical tube, after covering the lens and the eyepiece with special caps, is placed in the same case, but in a separate compartment. The goniometer is placed in the separate case that is carried in one of the ammunition wagon along with fuze-setter. The leather case is placed in a tarpaulin box and is tied to the outside of the front wall of the same wagon.
To focus the telescope, by loosening the butterfly nut (7) on the fixed drum, the goniometer together with the optical tube can be revolved about a vertical line. Looking either through lateral adjustment sight and the front-sight, or through the upper derivate of the optical tube, and rotating at the same time, the tube can be laid approximately at any point. Then, taking with the left hand the body of the tube, and with the right hand the knurled knob of the ocular, unscrew it from right to left until it stops, then, looking through the tube, turn the same knob slowly in reverse direction until the target is seen at best.
To lay the optical tube, at first lay the telescope in elevation. For this purpose rotate the tube in the coupling (2) until the divisions of the scale become vertical, then rotated it about its horizontal axis until the aiming point projects against the lower end of any of the scale divisions. Subsequently, laid the tube in direction, rotating it on its vertical axis as much as is necessary to bring the point of sight into line with the large vertical line of the scale, and then the goniometer butterfly nut (7) is fastened.
To measure the angular distances by determining immediately the corresponding division in millèmes :
1) Using the micrometre : point the telescope at the target, since each division correspond to a millème, it suffices to read the number of divisions which are included between the two points. This method is applied especially when measuring the lateral deviations of the shells from the target, but the micrometre of the telescope can only assess angular deviations of less than 60 millièmes.
2) Using the scale of the telescope dial plate : set the scale of the goniometer so that the indicator points to 1000. Lay the telescope at the first point, which must be the target, if the angular distance between it and any other point is determined; clamp the goniometer butterfly nut (7), then act on the handle (12) until a vertical line passes through the second point. By means of the indicators of the goniometer and of the lead screw read the division obtained, which is the angular distance between the two points. If the absolute height of the angular distance is required, the reported division is reduced by 1000. Since the scale of the telescope and the gun goniometer are the same, if the telescope is close to the gun, the division read on the telescope matches that of the gun.
To mark the normal height of burst of the shrapnel, look at the two horizontal lines that occupy the upper half of the telescope field of view : when the telescope is laid at the target so that the base of the target coincides with the lower edge of the vertical line, the first horizontal line marks the normal height of the lateral bursts above the target, and the upper line, marks the double normal height.
To measure the angle of sight using the micrometre, laid the telescope in direction, place the horizontal scale vertically and, with the help of the level, place the telescope horizontally, then look into the telescope and count the division against which the target is projected : this division expresses the angle of sight in millièmes. If the target is projected above the large horizontal line, this angle is positive, if it is below it, it is negatives.
The angle of sight can also be measured using the scale of the telescope dial plate, but only for angles between 90 and 30 millièmes. If the angle is greater, its measurement can be done either by successive directions of the telescope or by the scale of the fork.
SOURCE : Материалната часть на 75 м/м полско скорострелно оръдие образец 1904 година. II. Описание и употребление на мерните инструменти. Описание на предника и на зарядната ракла. Sofia : Придворна Печаница на Братия Прошекови 1906, pp. 21-29.