The SUIT sight is a 4×

prism sight A prism sight or prismatic sight, sometimes also called prism scope or prismatic scope, is a type of telescopic sight which uses a reflective prism for its erect image, image-erecting system, instead of the series of relay lenses found in traditio ...

with

tritium Tritium () or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with a half-life of ~12.33 years. The tritium nucleus (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus of the ...

-powered illumination, utilised at

dusk Dusk occurs at the darkest stage of twilight, or at the very end of astronomical twilight after sunset and just before nightfall.''The Random House College Dictionary'', "dusk". At predusk, during early to intermediate stages of twilight, enoug ...

dawn Dawn is the time that marks the beginning of twilight before sunrise. It is recognized by the diffuse sky radiation, appearance of indirect sunlight being Rayleigh scattering, scattered in Earth's atmosphere, when the centre of the Sun's disc ha ...

. The full name is the L2A2 Sight Unit Infantry Trilux. The sight is not designed as a

sniper A sniper is a military or paramilitary marksman who engages targets from positions of concealment or at distances exceeding the target's detection capabilities. Snipers generally have specialized training and are equipped with telescopic si ...

sight, but as a standard issue infantry sight to improve the infantryman's night fighting capability and to assist target identification at long range in daylight and in poor light conditions. The sight was mounted on the

L1A1 Self-Loading Rifle The L1A1 Self-Loading Rifle (SLR), also known by the initial Canadian designation C1, or in the U.S. as the "inch pattern" FAL, is a British version of the Belgian FN FAL battle rifle. The L1A1 was produced under licence and adopted by the arme ...

GPMG A general-purpose machine gun (GPMG) is an air-cooled, usually belt-fed machine gun that can be adapted flexibly to various tactical roles for light and medium machine guns. A GPMG typically features a quick-change barrel design calibered for ...

. The SUIT sight was developed in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

by Royal Armaments Research Development Establishment (RARDE) and is manufactured by Avimo Ltd., now known as

Thales Thales of Miletus ( ; ; ) was an Ancient Greek philosophy, Ancient Greek Pre-Socratic philosophy, pre-Socratic Philosophy, philosopher from Miletus in Ionia, Asia Minor. Thales was one of the Seven Sages of Greece, Seven Sages, founding figure ...

UK. It was first produced in 1976 by Avimo Ltd. in

London London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...

and is regarded as an early optical combat sight. The SUIT sight was an optional optical sighting system for the

British Army The British Army is the principal Army, land warfare force of the United Kingdom. the British Army comprises 73,847 regular full-time personnel, 4,127 Brigade of Gurkhas, Gurkhas, 25,742 Army Reserve (United Kingdom), volunteer reserve perso ...

and was also used by the Australians and New Zealanders. It was not widely issued amongst nor used in combat by the British Infantry, Royal Marines and

RAF Regiment The Royal Air Force Regiment (RAF Regiment) is part of the Royal Air Force and functions as a specialist corps. Founded by Royal Warrant in 1942, the Corps carries-out security tasks relating to the protection of assets and personnel dedicated ...

. A similar unit known as the

SUSAT The Sight Unit Small Arms, Trilux, or SUSAT, is a 4× telescopic sight, with Tritium illumination , tritium-powered illumination utilised at dusk or dawn. The full name of the current model is the SUSAT L9A1. The sight is not designed as a sniper ...

( Sight Unit Small Arms, Trilux) was fitted to the later SA80 series weapons.

L1A1 mounting system

The

FN FAL The FAL (, English: Light Automatic Rifle) is a battle rifle designed in Belgium by Dieudonné Saive and manufactured by FN Herstal and others since 1953. During the Cold War the FAL was adopted by many countries of the NATO, North Atlantic Trea ...

from which the L1A1 Self-Loading Rifle was derived was not designed for mounting optical sights like the SUIT. To mount the SUIT, a new top cover was designed. This had a rail welded to the top to accept the sight mount, and two tabs at the rear of the pressed sheet steel cover which butted against the back of the upper receiver, preventing the cover from sliding on its rails and affecting the weapon's zero. The custom top receiver cover rail mounting causes an offset of the optical sight axis to the left side in relation to the receiver and barrel center axis. This prismatic offset design of the sight helped to improve clearance around the action, reduce the overall length of the sight,

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

errors and heat mirage from the barrel as it heated up during firing. The mounting system was technically complex as it combined interfaces between the rifle and the top cover and the rail and the SUIT sight unit itself. Sight adjustment was performed on the front of the SUIT unit base for elevation and on the right bottom side for windage.

Range setting feature

The SUIT sight features a Bullet drop compensation (BDC, sometimes referred alternatively as ''ballistic elevation''). The range setting feature consists of a selection lever to select a pre-determined zero cam for (rear setting) or (forward setting) range. The feature is tuned only for the

ballistic trajectory In physics, projectile motion describes the motion of an object that is launched into the air and moves under the influence of gravity alone, with air resistance neglected. In this idealized model, the object follows a parabolic path determin ...

of a particular gun- cartridge combination with a predefined

projectile A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found ...

weight/type,

muzzle velocity Muzzle velocity is the speed of a projectile (bullet, pellet, slug, ball/ shots or shell) with respect to the muzzle at the moment it leaves the end of a gun's barrel (i.e. the muzzle). Firearm muzzle velocities range from approximately t ...

and

air density The density of air or atmospheric density, denoted '' ρ'', is the mass per unit volume of Earth's atmosphere at a given point and time. Air density, like air pressure, decreases with increasing altitude. It also changes with variations in atmosph ...

Reticle

The

reticle A reticle or reticule, also known as a graticule or crosshair, is a pattern of fine lines or markings built into the eyepiece of an optical device such as a telescopic sight, spotting scope, theodolite, optical microscope or the electronic v ...

of the SUIT sight is of unusual design. Unlike the traditional crosshair layouts commonly used, which are in essence a cross intersecting the target, the SUIT has a single

obelisk An obelisk (; , diminutive of (') ' spit, nail, pointed pillar') is a tall, slender, tapered monument with four sides and a pyramidal or pyramidion top. Originally constructed by Ancient Egyptians and called ''tekhenu'', the Greeks used th ...

-shaped post protruding from the top edge of the sight so as not to obscure the target. The reticle is

-illuminated for low-light condition aiming. The Trilux radioactive tritium illuminator light source produces a red glow, that can be selected and brightness adjusted on the top of the unit and has to be replaced every 8–12 years, since it gradually loses its brightness due to

radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

Body

The SUIT sight has an

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

body, into which the eyepiece, objective

lens A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'') ...

and prisms are fitted as assemblies.

Specifications

SUIT L2A2 *Overall dimensions: (L x W x H): 188 x 76 x 69 mm *Weight: 340 grams *

Magnification Magnification is the process of enlarging the apparent size, not physical size, of something. This enlargement is quantified by a size ratio called optical magnification. When this number is less than one, it refers to a reduction in size, so ...

: 4× *

Field of view The field of view (FOV) is the angle, angular extent of the observable world that is visual perception, seen at any given moment. In the case of optical instruments or sensors, it is a solid angle through which a detector is sensitive to elec ...

: 8 degrees (140 mils) *

Objective Objective may refer to: * Objectivity, the quality of being confirmed independently of a mind. * Objective (optics), an element in a camera or microscope * ''The Objective'', a 2008 science fiction horror film * Objective pronoun, a personal pron ...

diameter: 25.5 mm *

Exit pupil In optics, the exit pupil is a virtual aperture in an optical system. Only ray (optics), rays which pass through this virtual aperture can exit the system. The exit pupil is the image of the aperture stop in the optics that follow it. In a optic ...

: 6.375 mm *

Eye relief {{unref, date=June 2023 The eye relief of an optical instrument (such as a telescope, a microscope, or binoculars) is the distance from the last surface of an eyepiece within which the user's eye can obtain the full viewing angle. If a viewer's eye ...

: 35 mm *Light permeability: 86% *Reticle illumination: Red tritium, glass ampoule *Illumination strength: Adjustable *Tritium ampoule lifetime: 8–12 years *Range Settings: 300 meters (rear) or 500 meters (forward). *NATO Stock Number (NSN): 1240-99-964-7647 (Sight Unit Infantry Trilux (SUIT) L2A2)

References