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. The optical components may be combined with optoelectronics to add night vision or smart device features. History The first experiments directed to give shooters optical aiming aids go back to the early 17th century. For centuries, different optical aiming aids and primitive predecessors of telescopic sights were created that had practical or performance limitations. In the late 1630s, English amateur astronomer William Gascoigne was experimenting with a Keplerian telescope and left it with the case open. Later he found that a spider had spun its web inside the case, and when he looked through the telescope he found that the web was in focus with distant objects. Gascoigne realised that he could use this principle to make a telescopic sight for use in his astronomical observations. In 1776, Charles Willson Peale collaborated with David Rittenhouse to mount a telescope to a rifle as a sighting aid, but was unable to mount it sufficiently far forward to prevent the eyepiece impacting with the operator's eye during recoils. In the same year, James Lind and Captain Alexander Blair described a gun which included a telescopic sight. The first documented telescopic rifle sight was invented between 1835 and 1840. In a book titled The Improved American Rifle, written in 1844, British-American civil engineer John R. Chapman documented the first telescopic sights made by gunsmith Morgan James of Utica, New York. Chapman gave James the concepts and some of the design, whereupon they produced the Chapman-James sight. In 1855, optician William Malcolm of Syracuse, New York began producing his own telescopic sight, used an original design incorporating achromatic lenses such as those used in telescopes, and improved the windage and elevation adjustments. These Malcolm sights were between 3× and 20× magnification (possibly more). Malcolm's sights and those made by Vermont jeweller L. M. Amidon were the