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telescope

From The Columbia Encyclopedia
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 astronomical telescopes gather radio waves (see radio astronomy ), X rays (see X-ray astronomy ), or infrared or ultraviolet radiation. There are three major types of optical telescopes, classified according to the element that gathers and focuses the incoming light. In the refracting telescope, or refractor, light is bent, or refracted, as it passes through an objective lens. The objective lens is convex, i.e., thicker at the middle than the edges. Parallel light passing through the lens is refracted so that it converges to a point behind the lens, called the focus. The distance from the lens to the focus is called the focal length. In a reflecting telescope, or reflector, light is reflected by a concave mirror and brought…
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Full text Article telescope

From Astronomy Encyclopedia
Device that augments the ability of the eye to observe distant or faint objects, particularly celestial objects. The Egyptians were making glass around 3000BC, and the Greeks had a good understanding of the refraction and reflection of light by glass lenses in 300BC, but it was nearly two thousand…
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Full text Article telescope

From Philip's Encyclopedia
Instrument for enlarging a distant object or studying electromagnetic radiation from a distant source. Optical telescopes can use lenses (refracting telescopes) or mirrors (reflecting telescopes); catadioptric telescopes use both in combination. The lens or mirror is the telescope's main…
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Full text Article telescope

From The Columbia Encyclopedia
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 astronomical telescopes gather…
| 2,335 words
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Full text Article telescope

From The Macquarie Dictionary
an optical instrument for making distant objects appear nearer and larger. There are two principal forms, one (refracting telescope ) consisting essentially of a lens or object glass for forming an image of the object and an eyepiece or combination of lenses for magnifying this image, and the other…
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Full text Article TELESCOPE

From Gaither's Dictionary of Scientific Quotations
He [man] cannot but feel a sense of pleasure, and even of power, when the telescope reveals to his gaze not only the worlds that constitute his own so-called Solar System, but the suns that light up the borders of the Universe, system upon system, sun upon sun, covering the unbounded area almost as…
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Full text Article Telescopes

From Collins Stargazing: Beginners Guide to Astronomy
A reflecting telescope (the light-gathering...
Telescopes have been used for centuries to study the heavens in unprecedented detail. The first telescopes to be used in the early years of the seventeenth century were far less powerful than a modern pair of binoculars. Today, you can buy a very capable telescope for a reasonable price. CHOOSING…
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Full text Article telescope

From Britannica Concise Encyclopedia
Device that collects light from and magnifies images of distant objects, undoubtedly the most important investigative tool in astronomy . The first telescopes focused visible light by refraction through lens es; later instruments used reflection from curved mirrors ( see optics ). Their invention is…
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Full text Article telescope

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
Optical instrument that magnifies images of faint and distant objects; any device for collecting and focusing light and other forms of electromagnetic radiation. A telescope with a large aperture, or opening, can distinguish finer detail and fainter objects than one with a small aperture. The…
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Full text Article telescope

From The Chambers Dictionary
an optical instrument for viewing objects at a distance; a radio telescope (qv). vt to drive or slide one into another like the movable joints of a telescope; to compress, shorten, make smaller, etc; to compact, crush. vi to collapse part within part, like a telescope; to be compressed or compacted. …
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Full text Article telescope

From The Penguin Dictionary of Science
telescope Schematic representations of light...
An optical instrument for viewing distant objects in detail. Rays from an object are brought to a focus where they are magnified by an eyepiece, consisting of one or more lenses in combination. Different methods are used to focus the rays (see the diagram below). Refracting telescopes use lenses; …
| 211 words , 1 image
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