A monocular is a compact refracting telescope used to magnify images of distant objects, typically using an optical prism to ensure an erect image, instead of using relay lenses like most telescopic sights. The volume and weight of a monocular are typically less than half of a pair of binoculars with similar optical properties, making it more portable and also less expensive. This is because binoculars are essentially a pair of monoculars packed together — one for each eye. As a result, monoculars only produce two-dimensional images, while binoculars can use two parallaxed images to produce binocular vision, which allows stereopsis and depth perception.
Galilean type Soviet-made miniature 2.5 × 17.5 monocular
The highest specification 8× monocular from Opticron – 8×42 DBA
Two 8× monoculars showing eye lens diameter comparison
Asika 8×42 and Visionary 12×50 showing top-wheel focusing
A telescopic sight, commonly called a scope informally, is an optical sighting device based on a refracting telescope. It is equipped with some form of a referencing pattern – known as a reticle – mounted in a focally appropriate position in its optical system to provide an accurate point of aim. Telescopic sights are used with all types of systems that require magnification in addition to reliable visual aiming, as opposed to non-magnifying iron sights, reflector (reflex) sights, holographic sights or laser sights, and are most commonly found on long-barrel firearms, particularly rifles, usually via a scope mount. Similar devices are also found on other platforms such as artillery, tanks and even aircraft. The optical components may be combined with optoelectronics to add night vision or smart device features.
View through a 4× telescopic sight
Leupold and Stevens Mark 6 scope with variable magnification X3-X18, mounted on an M24 SWS
Telescopic sight (German made ZF Ajack 4×90 (4×38 in modern terminology) for the World War II pattern Swedish sniper rifle m/1941.
The Zielgerät ZG 1229 Vampir displayed by a British soldier (ca 1945)