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A prism paralleloscope is a piece kit used by artillery units as a gun aiming point. It is a type of paralleloscope that uses a prism instead of a plain mirror. Its purpose was to function as an aiming point in the horizontal plane when laying for indirect fire artillery.
The prism paralleloscope entered service with the British Army in the late 1950s. It was permanently fitted in a fibre-glass case with a lid. This case was mounted on two short metal vertical poles so that it was about 2 ft (0.6 m) above the ground, these vertical poles were held together by two horizontal rods slightly shorter that the paralleloscope case. Once mounted the lid of the case provided a 'canopy' above the paralleloscope.
Paralleloscopes entered British service in the 1920s-1930s. These early versions were a mirror about 3 ft (0.9 m) long and 4 in (100 mm) wide, mounted on a tripod about 3 ft (0.9 m) high and positioned a few yards (or meters) away from and to the side of a gun on its dial sight side. Each gun in a battery had at least one. When a gun was oriented in its centre of arc it recorded the paralleloscope as one of its aiming points (other types of aiming point were a distinctive distant topographical feature or a pair of aiming posts).
With a paralleloscope the gun layer set the zero line deflection or bearing of fire on his dial sight and aimed his sight at its reflection in the paralleloscope. As the gun fire and its trail(s) bedded in and the gun moved back, the reflected image of the sight moved along the paralleloscope. It was particularly useful at night because it removed the need for aiming points with lights attached to them. If the gun had a very wide arc of fire then more than one paralleloscope was required for each gun.
A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation.
A sundial is a device that tells the time of day when there is sunlight by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a flat plate and a gnomon, which casts a shadow onto the dial. As the Sun appears to move across the sky, the shadow aligns with different hour-lines, which are marked on the dial to indicate the time of day. The style is the time-telling edge of the gnomon, though a single point or nodus may be used. The gnomon casts a broad shadow; the shadow of the style shows the time. The gnomon may be a rod, wire, or elaborately decorated metal casting. The style must be parallel to the axis of the Earth's rotation for the sundial to be accurate throughout the year. The style's angle from horizontal is equal to the sundial's geographical latitude.
Indirect fire is aiming and firing a projectile without relying on a direct line of sight between the gun and its target, as in the case of direct fire. Aiming is performed by calculating azimuth and inclination, and may include correcting aim by observing the fall of shot and calculating new angles.
A periscope is an instrument for observation over, around or through an object, obstacle or condition that prevents direct line-of-sight observation from an observer's current position.
A theodolite is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying, but they are also used extensively for building and infrastructure construction, and some specialized applications such as meteorology and rocket launching.
External ballistics or exterior ballistics is the part of ballistics that deals with the behavior of a projectile in flight. The projectile may be powered or un-powered, guided or unguided, spin or fin stabilized, flying through an atmosphere or in the vacuum of space, but most certainly flying under the influence of a gravitational field.
Levelling or leveling is a branch of surveying, the object of which is to establish or verify or measure the height of specified points relative to a datum. It is widely used in cartography to measure geodetic height, and in construction to measure height differences of construction artifacts. It is also known as spirit levelling and differential levelling.
Iron sights are a system of shaped alignment markers used as a sighting device to assist in the aiming of a device such as a firearm, crossbow, or telescope, and exclude the use of optics as in reflector (reflex) sights, holographic sights, and telescopic sights.
A milliradian is an SI derived unit for angular measurement which is defined as a thousandth of a radian. Milliradians are used in adjustment of firearm sights by adjusting the angle of the sight compared to the barrel. Milliradians are also used for comparing shot groupings, or to compare the difficulty of hitting different sized shooting targets at different distances. When using a scope with both mrad adjustment and a reticle with mrad markings, the shooter can use the reticle as a "ruler" to count the number of mrad's a shot was off target, which directly translates to the sight adjustment needed to hit the target with a follow up shot. Optics with mrad markings in the reticle can also be used to make a range estimation of a known size target, or vice versa, to determine a target size if the distance is known, a practice called "milling".
In field artillery, the accuracy of indirect fire depends on the use of aiming points. In air force terminology the aiming point refers to holding the intersection of the cross hairs on a bombsight when fixed at a specific target.
Gun laying is the process of aiming an artillery piece or turret, such as a gun, howitzer, or mortar, on land, in air, or at sea, against surface or aerial targets. It may be laying for direct fire, where the gun is aimed similarly to a rifle, or indirect fire, where firing data is calculated and applied to the sights. The term includes automated aiming using, for example, radar-derived target data and computer-controlled guns.
A level is an optical instrument used to establish or verify points in the same horizontal plane in a process known as levelling, and is used in conjunction with a levelling staff to establish the relative heights levels of objects or marks. It is widely used in surveying and construction to measure height differences and to transfer, measure, and set heights of known objects or marks.
The meridian circle is an instrument for timing of the passage of stars across the local meridian, an event known as a culmination, while at the same time measuring their angular distance from the nadir. These are special purpose telescopes mounted so as to allow pointing only in the meridian, the great circle through the north point of the horizon, the north celestial pole, the zenith, the south point of the horizon, the south celestial pole, and the nadir. Meridian telescopes rely on the rotation of the sky to bring objects into their field of view and are mounted on a fixed, horizontal, east–west axis.
The Mark 12 5"/38 caliber gun was a United States naval gun. The gun was installed into Single Purpose and Dual Purpose mounts used primarily by the US Navy. On these 5" mounts, Single Purpose (SP) means that the mount is limited to 35° elevation with no provision for AA shell fuze setters, and is designed to fire at surface targets only. Dual Purpose (DP) means that it is designed to be effective against both surface and aircraft targets because it can elevate to 85° and has on mount AA shell fuze setters. The 38 caliber barrel was a mid-length compromise between the previous United States standard 5"/51 low-angle gun and 5"/25 anti-aircraft gun. United States naval gun terminology indicates the gun fired a projectile 5 inches (127 mm) in diameter, and the barrel was 38 calibers long, making the 5"/38 dual purpose midway in barrel length between the 5"/51 surface-to-surface and the 5"/25 anti-aircraft guns. The increased barrel length provided greatly improved performance in both anti-aircraft and anti-surface roles compared to the 5"/25 gun. However, except for the barrel length and the use of semi-fixed ammunition, the 5"/38 gun was derived from the 5"/25 gun. Both weapons had power ramming, which enabled rapid fire at high angles against aircraft. The 5"/38 entered service on USS Farragut, commissioned in 1934. The base ring mount, which improved the effective rate of fire, entered service on USS Gridley, commissioned in 1937.
The Iowa-class battleships were the most heavily armed gunships the United States Navy has ever put to sea due to the continual development of their onboard weaponry. The first Iowa-class ship was laid down in June 1940; in their World War II configuration, each of the Iowa-class battleships had a main battery of 16-inch (406 mm) guns that could hit targets nearly 20 statute miles (32 km) away with a variety of artillery shells designed for anti-ship or bombardment work. The secondary battery of 5-inch (127 mm) guns could hit targets nearly 9 statute miles (14 km) away with solid projectiles or proximity fuzed shells, and were effective in an anti-aircraft role as well. Each of the four battleships carried a wide array of 20 mm and 40 mm anti-aircraft guns for defense against enemy aircraft.
A weapon mount is an assembly or mechanism used to hold a weapon onto an platform in order for it to function at maximum capacity. Weapon mounts can be broken down into two categories: static mounts and non-static mounts.
In the U.S. Army Coast Artillery Corps, the term fire control system was used to refer to the personnel, facilities, technology and procedures that were used to observe designated targets, estimate their positions, calculate firing data for guns directed to hit those targets, and assess the effectiveness of such fire, making corrections where necessary.
The directing point (DP) was a term used in the U.S. Coast Artillery to identify a precisely surveyed point that was used as the point of reference for preparing the firing data used to aim the guns of a given Coast Artillery battery.
The T-54 and T-55 combines a high-velocity gun with a highly mobile chassis, low silhouette, and exceptional long-range endurance. The T-54/55 tanks have been produced in greater quantity than any other tank in the world. Seven main production models have been widely used throughout the Warsaw Pact and in many other countries. The T-54/55 series has been manufactured in Czechoslovakia and Poland as well as in China where it is known as Type 59. More than a dozen countries have produced upgraded T-55 variants with similar capabilities in protection and lethality. The tank featured many innovations, many of these being in the fire controls of the T-54 and the T-55.
The depression range finder (DRF) was a fire control device used to observe the target's range and bearing to calculate firing solutions when gun laying in coastal artillery. It was the main component of a vertical base rangefinding system. It was necessitated by the introduction of rifled artillery from the mid-19th century onwards, which had much greater ranges than the old smoothbore weapons and were consequently more difficult to aim accurately. The DRF was invented by Captain H.S.S. Watkin of the Royal Artillery in the 1870s and was adopted in 1881. It could provide both range and bearing information on a target. The device's inventor also developed a family of similar devices, among them the position finder, which used two telescopes as a horizontal base rangefinding system, around the same time; some of these were called electric position finders. Some position finders retained a depression range finding capability; some of these were called depression position finders. Watkin's family of devices were deployed in position finding cells, a type of fire control tower, often in configurations that allowed both horizontal base and vertical base rangefinding. Watkin's system included automatic electrical updating of range and bearing dials near the guns as the position finders were manipulated, and a system of remotely firing the guns electrically from the position finding cell. The improved system was trialled in 1885 and widely deployed in the 1890s. Functionally equivalent devices were developed for the United States Army Coast Artillery Corps and its predecessors, called depression position finders or azimuth instruments depending on function, adopted in 1896 and deployed widely beginning in the early 1900s as the Endicott program of modern coastal defences was built. These devices were also used by both countries to control submarine (underwater) minefields.