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 ?
The larger the twilight factor, the better a binocular is for low-light observing.
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Johnson-Stewart contracted product management services leader Innovation Direct[TM] to represent the Binocular Wear to potential licensees for a 2 year period.
The effects of errors in binocular motor control and in sensory fusion of the two images
The right binocular makes the scene look brighter than it actually is.
Binocular could be joined by Spirit Son on the Champion Hurdle trail on the strength of his novice campaign, which included a 13-length defeat of Cue Card at Aintree.
THAT'S CHAMPION Tony McCoy milks the reception as the returns to the winner's enclosure after he had powered to Champion Hurdle success on the impressive Binocular
Binoculars are our common passion their history, the technology and the valuable early models must be preserved for future generations," emphasizes Richard Schmidt, Managing Director of Carl Zeiss Sports Optics GmbH.
Generally, I wear a binocular on a short neck strap.
19, 2011 /PRNewswire/ -- Life's "can't miss" moments are now easier to observe and capture with the world's first digital binoculars to record in AVCHD(TM) 2.
In addition, any tripod that collapses small enough to fit in your luggage will not be sturdy enough for serious binocular observing.
With Overturn adopting his customary front-running tactics, Tony McCoy on Binocular and Ruby Walsh on the progressive Rock On Ruby stalked his every move.