The first attempts to equip guns with sniper sights were made during the Wild West times in the USA in the 19th century. The idea was to fix a telescopic tube to a rifle, replacing standard sights with it. A crosshair of thin metal rods on one of the lenses of the telescopic tube was used to aim the target.

At first sniper sights were cumbersome – their length exceeded the length of the rifle itself and their accuracy left much to be desired. That situation changed during World War I (1914-1918), when the sniper sights were significantly modernized and became widespread in the armies of all the warring parties. As a result of the refinement, the telescopic sight became removable, its weight and dimensions were reduced, and its optical capabilities were improved by prismatic lenses.

After the Second World War in 1949 the American inventor Frederick Kales developed a telescopic sight with variable magnification, and in 1953 a telescopic sight with electronic illumination was adopted by the US Army. Since then optical sights design has not undergone significant changes.

Optical sights
An optical sight is an optical tube with several lenses and a reticle. Typically, such sights have a magnification of 2x to 20x. Also they have correction mechanism – vertical and horizontal. The corrections are made by rotating two corresponding screws.

In order to make a shot with a telescopic sight, it is enough to connect the crosshairs with the enlarged image of the target. Also, some models of scopes are equipped with LED illumination, which allows you to aim in poor lighting conditions, such as at dusk.

Advantages of telescopic sights:
possibility of repair in the field;
Possibility to use in any weather conditions and temperatures;
High accuracy at great distances.

Optical sights are quite reliable, but they can fail from mechanical impacts, so they require some caution in use. It is also extremely difficult to fire at close range from a telescopic sight, especially at moving targets.