A telescope is an instrument designed for the observation of remote objects.
The term usually refers to optical telescopes, but there are telescopes for most of the spectrum of electromagnetic radiation and for other signal types.
An optical telescope gathers and focuses visible light and other electromagnetic radiation.
Telescopes increase the apparent angular size of distant objects, as well as their apparent brightness.
Telescopes work by employing one or more curved optical elements - lenses or mirrors - to gather light or other electromagnetic radiation and bring that light or radiation to a focus, where the image can be observed, photographed or studied.
Optical telescopes are used for astronomy and in many non-astronomical instruments including theodolites, transits, spotting scopes, monoculars, binoculars, camera lenses and spyglasses.
Radio telescope A radio telescope is a form of radio receiver used in astronomy. In contrast to an "ordinary" telescope, which receives visible light, a radio ... >
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Active optics Active optics is a relatively new technology for reflecting telescopes developed in the 1980s, which has more recently enabled the construction of a ... >
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European Southern Observatory The European Southern Observatory (ESO, also more formally the European Organisation for Astronomical Research in the Southern Hemisphere) is an ... >
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Astrophysics Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties (luminosity, density, ... >
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Chandra X-ray Observatory Chandra X-ray Observatory is a satellite launched on STS-93 by NASA on July 23, 1999. It was named in honor of Indian-American physicist Subrahmanyan ... >
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Quasar A quasar is an astronomical source of electromagnetic energy, including light, which shows a very high redshift. The scientific consensus is that ... >
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Hubble Deep Field The Hubble Deep Field (HDF) is an image of a small region of the sky, based on the results of a series of observations by the Hubble Space Telescope. ... >
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