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California Extremely Large Telescope
The California Extremely Large Telescope (CELT) was a proposal for an extremely large telescope design first proposed in the 1990s by a consortium of Californian Universities. The design was for a segmented 30 m diameter astronomical telescope. The CELT had a positive reception and continued to be developed, and was renamed the Thirty Meter Telescope (TMT) around 2003–4. The CELT was one of the earlier and more successful proposals for extremely large telescopes. The optical design for CELT is a Ritchey-Chretien two-mirror system, with a segmented mirror mosaic with 1080 segments. This rather naturally provides a large, 20 arcminute field of view with less than 0.5 arcsecond images (100% enclosed energy). This focus is free of coma and only suffers from astigmatism, which grows quadratically with field angle. The primary was planned to be in diameter, and for compactness, the primary f-number will be f/1.5. The final focus will be f/15, delivering a final foc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extremely Large Telescope
The Extremely Large Telescope (ELT) is an astronomical observatory currently under construction. When completed, it is planned to be the world's largest optical/near-infrared extremely large telescope. Part of the European Southern Observatory (ESO) agency, it is located on top of Cerro Armazones in the Atacama Desert of northern Chile. The design consists of a reflecting telescope with a segmented primary mirror and a diameter secondary mirror, and will be supported by adaptive optics, eight laser guide star units and multiple large science instruments. The observatory aims to gather 100 million times more light than the human eye, 13 times more light than the largest optical telescopes existing in 2014, and be able to correct for atmospheric distortion. It has around 256 times the light gathering area of the Hubble Space Telescope and, according to the ELT's specifications, would provide images 16 times sharper than those from Hubble. The project was originally called ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thirty Meter Telescope
The Thirty Meter Telescope (TMT) is a planned extremely large telescope (ELT) that has become controversial due to its location on Mauna Kea, on the island of Hawaiʻi. The TMT would become the largest visible-light telescope on Mauna Kea. Scientists have been considering ELTs since the mid 1980s. In 2000, astronomers considered the possibility of a telescope with a light-gathering mirror larger than 20 meters (65') in diameter. The technology to build a mirror larger than 8.4 meters (28') does not exist; instead scientists considered using either small segments that create one large mirror, or a grouping of larger 8-meter (26') mirrors working as one unit. The US National Academy of Sciences recommended a 30-meter (100') telescope be the focus of U.S. interests, seeking to see it built within the decade. Scientists at the University of California and Caltech began development of a design that would eventually become the TMT, consisting of a 492-segment primary mirror with n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Segmented Mirror
A segmented mirror is an array of smaller mirrors designed to act as segments of a single large curved mirror. The segments can be either spherical or asymmetric (if they are part of a larger parabolic reflector). They are used as objectives for large reflecting telescopes. To function, all the mirror segments have to be polished to a precise shape and actively aligned by a computer-controlled active optics system using actuators built into the mirror support cell. The concept was pioneered by Guido Horn D'Arturo, who built the first working segmented mirror in 1952, after twenty years of research; It was later independently rediscovered and further developed under the leadership of Dr. Jerry Nelson at the Lawrence Berkeley National Laboratory and University of California during the 1980s, and since then all the necessaries technologies have spread worldwide to the point that essentially all future large optical telescopes plan to use segmented mirrors. Application There i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Field Of View
The field of view (FoV) is the extent of the observable world that is seen at any given moment. In the case of optical instruments or sensors it is a solid angle through which a detector is sensitive to electromagnetic radiation. Humans and animals In the context of human and primate vision, the term "field of view" is typically only used in the sense of a restriction to what is visible by external apparatus, like when wearing spectacles or virtual reality goggles. Note that eye movements are allowed in the definition but do not change the field of view when understood this way. If the analogy of the eye's retina working as a sensor is drawn upon, the corresponding concept in human (and much of animal vision) is the visual field. It is defined as "the number of degrees of visual angle during stable fixation of the eyes".Strasburger, Hans; Pöppel, Ernst (2002). Visual Field. In G. Adelman & B.H. Smith (Eds): ''Encyclopedia of Neuroscience''; 3rd edition, on CD-ROM. El ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coma (optics)
In optics (especially telescopes), the coma (), or comatic aberration, in an optical system refers to aberration inherent to certain optical designs or due to imperfection in the lens or other components that results in off-axis point sources such as stars appearing distorted, appearing to have a tail (coma) like a comet. Specifically, coma is defined as a variation in magnification over the entrance pupil. In refractive or diffractive optical systems, especially those imaging a wide spectral range, coma can be a function of wavelength, in which case it is a form of chromatic aberration. Overview Coma is an inherent property of telescopes using parabolic mirrors. Unlike a spherical mirror, a bundle of parallel rays parallel to the optical axis will be perfectly focused to a point (the mirror is free of spherical aberration), no matter where they strike the mirror. However, this is only true if the rays are parallel to the axis of the parabola. When the incoming rays strike the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astigmatism (optical Systems)
An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances. The term comes from the Greek α- (''a-'') meaning "without" and στίγμα (''stigma''), "a mark, spot, puncture". Forms of astigmatism There are two distinct forms of astigmatism. The first is a third-order aberration, which occurs for objects (or parts of objects) away from the optical axis. This form of aberration occurs even when the optical system is perfectly symmetrical. This is often referred to as a "monochromatic aberration", because it occurs even for light of a single wavelength. This terminology may be misleading, however, as the ''amount'' of aberration can vary strongly with wavelength in an optical system. The second form of astigmatism occurs when the optical system is not symmetric a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
F-number
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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Very Large Optical Telescope
Very may refer to: * English's prevailing intensifier Businesses * The Very Group, a British retail/consumer finance corporation ** Very (online retailer), their main e-commerce brand * VERY TV, a Thai television channel Places * Véry, a commune in Meuse department, France * Very (lunar crater), on the Moon * Very (Martian crater), on Mars Music * ''Very'' (Pet Shop Boys album), 1993 * ''Very'' (Dreamscape album), 1999 * ''Very'', an album by Miki Furukawa, 2010 People * Edward Wilson Very (1847–1910), US Navy officer, inventor of the Very flare gun * Frank Washington Very (1852–1927), American astronomer * Jones Very (1813–1880), American poet, essayist, clergyman and mystic * Lydia Louisa Anna Very (1823–1901), American author and illustrator * Pierre Véry (1900–1960), French novelist and screenwriter * Very Idham Henyansyah (born 1978), Indonesian serial killer Other uses * Very, the most common type of flare gun See also * Vary, a village in Uk ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giant Segmented Mirror Telescope
In folklore, giants (from Ancient Greek: ''gigas'', cognate giga-) are beings of human-like appearance, but are at times prodigious in size and strength or bear an otherwise notable appearance. The word ''giant'' is first attested in 1297 from Robert of Gloucester's chronicle. It is derived from the ''Gigantes'' ( grc-gre, Γίγαντες) of Greek mythology. Fairy tales such as ''Jack the Giant Killer'' have formed the modern perception of giants as dimwitted ogres, sometimes said to eat humans, while other giants tend to eat the livestock. The antagonist in '' Jack and the Beanstalk'' is often described as a giant. In some more recent portrayals, like those of Jonathan Swift and Roald Dahl, some giants are both intelligent and friendly. Literary and cultural analysis Giants appear in the folklore of cultures worldwide as they represent a relatively simple concept. Representing the human body enlarged to the point of being monstrous, giants evoke terror and remind hum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extremely Large Telescope
The Extremely Large Telescope (ELT) is an astronomical observatory currently under construction. When completed, it is planned to be the world's largest optical/near-infrared extremely large telescope. Part of the European Southern Observatory (ESO) agency, it is located on top of Cerro Armazones in the Atacama Desert of northern Chile. The design consists of a reflecting telescope with a segmented primary mirror and a diameter secondary mirror, and will be supported by adaptive optics, eight laser guide star units and multiple large science instruments. The observatory aims to gather 100 million times more light than the human eye, 13 times more light than the largest optical telescopes existing in 2014, and be able to correct for atmospheric distortion. It has around 256 times the light gathering area of the Hubble Space Telescope and, according to the ELT's specifications, would provide images 16 times sharper than those from Hubble. The project was originally called ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colossus Telescope
The Extremely Large Telescope (ELT) is an astronomical observatory currently under construction. When completed, it is planned to be the world's largest optical/ near-infrared extremely large telescope. Part of the European Southern Observatory (ESO) agency, it is located on top of Cerro Armazones in the Atacama Desert of northern Chile. The design consists of a reflecting telescope with a segmented primary mirror and a diameter secondary mirror, and will be supported by adaptive optics, eight laser guide star units and multiple large science instruments. The observatory aims to gather 100 million times more light than the human eye, 13 times more light than the largest optical telescopes existing in 2014, and be able to correct for atmospheric distortion. It has around 256 times the light gathering area of the Hubble Space Telescope and, according to the ELT's specifications, would provide images 16 times sharper than those from Hubble. The project was originally ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
