binocular


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binocular,

small optical instrument consisting of two similar telescopestelescope,
traditionally, a system of lenses, mirrors, or both, used to gather light from a distant object and form an image of it. Traditional optical telescopes, which are the subject of this article, also are used to magnify objects on earth and in astronomy; other types of
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 mounted on a single frame so that separate images enter each of the viewer's eyes. As with a single telescope, distant objects appear magnified, but the binocular has the additional advantage that it substantially increases the range of depth perception of the viewer because the magnified images are seen with both eyes. The frame of a binocular is usually hinged to permit adjustment of the distance between the telescopes. Focusing can be done by means of a wheel on the central axis between the telescopes; turning the wheel changes the distance from the objective lenses of the telescopes to the eyepieces. Separate focusing of each telescope from the eyepiece may be provided in some types of binocular. The term binocular now usually refers to the prism binocular, in which light entering each telescope through its objective lens is bent first one way and then the other by a pair of prisms before passing through one or more additional lenses in the eyepiece. The prisms aid in reducing the length of the instrument and in enhancing the viewer's depth perception by increasing the distance between the objective lenses. Other types of binocular include the opera glass and the field glass; both use Galilean telescopes, which do not employ prisms and which usually have less magnifying power than the telescopes in prism binoculars. A binocular is often specified by an expression such as "7×35" or "8×50"—the first number indicates how many times the binocular magnifies an object and the second number is the diameter of either objective lens in millimeters. The size of an objective lens is a measure of how much light it can gather for effective viewing.

Bibliography

See J. T. Kozak, Deep-Sky Objects for Binoculars (1988).

binocular

[bī′näk·yə·lər]
(biology)
Of, pertaining to, or used by both eyes.
Of a type of visual perception which provides depth-of-field focus due to angular difference between the two retinal images.
(optics)
Any optical instrument designed for use with both eyes to give enhanced views of distant objects, whose distinguishing performance feature is the depth perception obtainable.
References in periodicals archive ?
Contributing Editor JERRY OLTION uses binoculars ranging from 7x25 to 300x317.
Looking through a wobbly binocular is like trying to read fine print when traveling in an automobile over a rough road.
The second number is the aperture of the binoculars - the width of the main lens at the front - measured in millimetres.
The binoculars feature rubber armor protection for a firm grip with or without gloves.
But farther left of Albireo on the December map you'll find Sagitta and Delphinus, small constellations that fit into one or two binocular fields of view.
Twilight factor provides an indication of the relative performance of sizes of optics in low-light levels, and it is dependent on both the objective diameter (how much light enters the binocular or scope) and the exit pupil (how much light passes from the binocular or scope to the eye).
TIME WAS, FINDING A DECENT PAIR OF BINOCULARS without spending a fortune was tough to do, hut not any more.
Potential licensees in the eyewear products industry are currently being targeted as candidates to eventually commercialize the Binocular Wear on a worldwide basis.
The development and characteristics of binocular vision
Binoculars are an ideal solution for the weight-conscious traveller, as they can be used for other activities such as bird watching, in addition to astronomy.
Peddlers Cross has already beaten Binocular, though I doubt Nicky Henderson's horse was 100 per cent.
Auctioneer Andrew Aldridge said yesterday: "We knew about the crow's nest key but we never knew this second key for a binocular box on the Titanic existed until recently.