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binoculars
binoculars A pair of low-power telescopes mounted side by side so that both eyes can be used simultaneously. Conventional prismatic binoculars use a pair of Porro prisms to fold each light path, thus shortening the distance between the objective lenses and the eyepieces. These prisms also erect the image. An alternative to Porro prisms are roof prisms, which do the same thing but more compactly since the light emerges along the same axis as it enters. Binoculars are specified by a pair of numbers, such as 7 × 50. The first number refers to the magnification, and the second to the aperture in millimetres. Sizes commonly used for astronomy are 7 × 50, 10 × 50, and 11 × 80. The aperture divided by the magnification gives the size, in millimetres, of the exit pupil. Amateur astronomers use binoculars for observing comets and large deep-sky objects such as star clusters, nebulae, and galaxies. They are also useful for locating stars somewhat fainter than can be seen by the naked eye, and for observing the brighter variable stars.
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"binoculars." A Dictionary of Astronomy. 1997. Encyclopedia.com. 30 May. 2012 <http://www.encyclopedia.com>. "binoculars." A Dictionary of Astronomy. 1997. Encyclopedia.com. (May 30, 2012). http://www.encyclopedia.com/doc/1O80-binoculars.html "binoculars." A Dictionary of Astronomy. 1997. Retrieved May 30, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-binoculars.html |
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binoculars
bin·oc·u·lars / biˈnäkyələrz/ • pl. n. an optical instrument with a lens for each eye, used for viewing distant objects. |
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Cite this article
"binoculars." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 30 May. 2012 <http://www.encyclopedia.com>. "binoculars." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (May 30, 2012). http://www.encyclopedia.com/doc/1O999-binoculars.html "binoculars." The Oxford Pocket Dictionary of Current English. 2009. Retrieved May 30, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-binoculars.html |
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binoculars
binoculars
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Cite this article
"binoculars." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. 30 May. 2012 <http://www.encyclopedia.com>. "binoculars." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. (May 30, 2012). http://www.encyclopedia.com/doc/1O233-binoculars.html "binoculars." Oxford Dictionary of Rhymes. 2007. Retrieved May 30, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O233-binoculars.html |
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