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Chinese Future Giant Telescope
The Chinese Future Giant Telescope is a proposed optical telescope with a primary mirror that has a 30-meter diameter. Major characteristics The Chinese Future Giant Telescope has a primary focal ratio of 1.2. Its primary mirror is segmented with 1020 annular submirrors arranged in 17 concentric annuli. Each segment has average length and width both of 0.8 m. Apart from a conventional Cassegrain focus, four Nasmyth telescope, Nasmyth foci on two double-deck platforms on both sides are also present. There is a Coudé focus provided for there interferometric array. The comparatively small secondary mirror is 2.74 m in diameter, which will serve active corrections. Other characteristics include: #Partial annular submirrors #One of coude planar mirrors is aspherical; better image quality is obtained from such a system. #A pair of lens-prisms are used in a wide field of view system. Better image quality is obtained and atmospheric dispersion is corrected. See also * Lists of telesc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Telescope
An optical telescope is a telescope that gathers and focuses light mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct visual inspection, to make a photograph, or to collect data through electronic image sensors. There are three primary types of optical telescope: * Refracting telescopes, which use lenses and less commonly also prisms ( dioptrics) * Reflecting telescopes, which use mirrors ( catoptrics) * Catadioptric telescopes, which combine lenses and mirrors An optical telescope's ability to resolve small details is directly related to the diameter (or aperture) of its objective (the primary lens or mirror that collects and focuses the light), and its light-gathering power is related to the area of the objective. The larger the objective, the more light the telescope collects and the finer detail it resolves. People use optical telescopes (including monoculars and binoculars) for outdoor activities such as obser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primary Mirror
A primary mirror (or primary) is the principal light-gathering surface (the objective) of a reflecting telescope. Description The primary mirror of a reflecting telescope is a spherical or parabolic shaped disks of polished reflective metal ( speculum metal up to the mid 19th century), or in later telescopes, glass or other material coated with a reflective layer. One of the first known reflecting telescopes, Newton's reflector of 1668, used a 3.3 cm polished metal primary mirror. The next major change was to use silver on glass rather than metal, in the 19th century such was with the Crossley reflector. This was changed to vacuum deposited aluminum on glass, used on the 200-inch Hale telescope. Solid primary mirrors have to sustain their own weight and not deform under gravity, which limits the maximum size for a single piece primary mirror. Segmented mirror configurations are used to get around the size limitation on single primary mirrors. For example, the Gia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focal Ratio
In optics, the f-number of an optical system such as a camera lens is the ratio of the system's focal length to the diameter of the entrance pupil ("clear aperture").Smith, Warren ''Modern Optical Engineering'', 4th Ed., 2007 McGraw-Hill Professional, p. 183. It is also known as the focal ratio, f-ratio, or f-stop, and is very important in photography. It is a dimensionless number that is a quantitative measure of lens speed; increasing the f-number is referred to as ''stopping down''. The f-number is commonly indicated using a lower-case hooked f with the format ''N'', where ''N'' is the f-number. The f-number is the reciprocal of the relative aperture (the aperture diameter divided by focal length). Notation The f-number is given by: N = \frac \ where f is the focal length, and D is the diameter of the entrance pupil (''effective aperture''). It is customary to write f-numbers preceded by "", which forms a mathematical expression of the entrance pupil diameter in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cassegrain Focus
The Cassegrain reflector is a combination of a primary concave mirror and a secondary convex mirror, often used in optical telescopes and Antenna (radio), radio antennas, the main characteristic being that the optical path folds back onto itself, relative to the optical system's primary mirror entrance aperture. This design puts the Focus (optics), focal point at a convenient location behind the primary mirror and the convex secondary adds a Telephoto lens, telephoto effect creating a much longer focal length in a mechanically short system. In a symmetrical Cassegrain both mirrors are aligned about the optical axis, and the primary mirror usually contains a hole in the center, thus permitting the light to reach an eyepiece, a camera, or an image sensor. Alternatively, as in many radio telescopes, the final focus may be in front of the primary. In an asymmetrical Cassegrain, the mirror(s) may be tilted to avoid obscuration of the primary or to avoid the need for a hole in the prima ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nasmyth Telescope
The Nasmyth telescope, also called Nasmyth–Cassegrain or Cassegrain–Nasmyth, is a reflecting telescope developed by the Scottish inventor James Nasmyth. It is a modified form of a Cassegrain telescope, with light reflected sideways to an eyepiece. Scheme As in the Cassegrain telescope, the light falls on a concave primary mirror, then is reflected towards a convex secondary mirror. A comparatively small tertiary flat mirror reflects the light to one of the sides of the telescope. (The central hole in the primary mirror may still host a Cassegrain focus if the tertiary can be moved out of the way.) This flat mirror is placed on the altitude axis, so that the beam exits through a hole in the middle of the altitude bearing. This means the eyepiece or instrument does not need to move up and down with the telescope as the tertiary mirror's angle with the main telescope axis is adjustable as a function of the telescope's pointing and the star's elevation above the horizon; therefor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lists Of Telescopes
This is a list of lists of telescopes. * List of astronomical interferometers at visible and infrared wavelengths * List of astronomical observatories * List of highest astronomical observatories *List of large optical telescopes * List of largest infrared telescopes *List of largest optical telescopes historically *List of largest optical telescopes in the 18th century *List of largest optical telescopes in the 19th century *List of largest optical telescopes in the 20th century *List of largest optical reflecting telescopes *List of largest optical refracting telescopes *List of optical telescopes * List of proposed space observatories * List of radio telescopes *List of solar telescopes *List of space telescopes *List of telescopes of Australia * List of largest optical telescopes in the British Isles * List of telescope parts and construction *List of telescope types * List of the largest optical telescopes in North America * List of X-ray space telescopes See also * Lists o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chinese Telescopes
Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of various ethnicities in contemporary China ** Han Chinese, the largest ethnic group in the world and the majority ethnic group in Mainland China, Hong Kong, Macau, Taiwan, and Singapore ** Ethnic minorities in China, people of non-Han Chinese ethnicities in modern China ** Ethnic groups in Chinese history, people of various ethnicities in historical China ** Nationals of the People's Republic of China ** Nationals of the Republic of China ** Overseas Chinese, Chinese people residing outside the territories of Mainland China, Hong Kong, Macau, and Taiwan * Sinitic languages, the major branch of the Sino-Tibetan language family ** Chinese language, a group of related languages spoken predominantly in China, sharing a written script (Chinese ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
