The rangefinder for sale is one of many of several instruments used to measure the distance from the instrument to a selected point or object. One basic type is the optical range finder modeled after a ranging device developed by the Scottish firm of Barr and Stroud in the 1880s. The optical range finder is usually classified into two kinds, coincidence and stereoscopic.
The coincidence rangefinder for sale, used chiefly in cameras and for surveying, consists of an arrangement of lenses and prisms set at each end of a tube with a single eyepiece at its centre. This instrument enables the user to sight an object by correcting the parallax resulting from viewing simultaneously from two slightly separated points. The object’s range is determined by measuring the angles formed by a line of sight at each end of the tube; the smaller the angles produced, the greater is the distance, and vice versa. The stereoscopic rangefinder for sale operates on much the same principle and resembles the coincidence type except that it has two eyepieces instead of one. The design of the stereoscopic instrument makes it more effective for sighting moving objects. It was widely used for land-gunnery ranging during World War II.