A Schmidt camera, also referred to as the Schmidt telescope, is an astronomical camera designed to provide wide fields of view with limited aberrations. Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study A camera is a device used to capture images either as still Photographs or as sequences of moving images ( Movies or Videos. The field of view (also field of vision) is the angular extent of the observable world that is seen at any given moment Aberrations are departures of the performance of an optical system from the predictions of Paraxial optics. Other similar designs are the Wright Camera and Lurie-Houghton telescope. In 1935 just a few years after the introduction of the Schmidt camera, Franklin Wright (Berkley California presented his "short" alternative to the original arrangement
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Invention and design
The Schmidt camera was invented by Bernhard Schmidt in 1930[1]. Bernhard Woldemar Schmidt ( March 30, 1879 &ndash December 1, 1935) was an Estonian Swede Optician who spent his adult Year 1930 ( MCMXXX) was a Common year starting on Wednesday (link will display 1930 calendar of the Gregorian calendar. Its optical components are an easy-to-make spherical primary mirror, and an aspherical correcting lens, known as a corrector plate, located at the center of curvature of the primary mirror. "Globose" redirects here See also Globose nucleus. A sphere (from Greek σφαίρα - sphaira, "globe A primary mirror (or primary) is the principal Light -gathering surface of a reflective Telescope. A lens is an optical device with perfect or approximate Axial symmetry which transmits and refracts Light, converging or diverging A Schmidt corrector plate, invented by Bernhard Schmidt in 1930[http //www The film or other detector is placed inside the camera, at the prime focus. The design is noted for allowing very fast focal ratios, while controlling coma and astigmatism. In Optics (especially Telescopes, the coma (aka comatic aberration) in an optical system refers to aberration inherent to certain optical See also Aberration in optical systems, Astigmatism (eye An Optical system with astigmatism is one where rays that propagate
Schmidt cameras have very strongly curved focal planes, thus requiring that the film, plate, or other detector be correspondingly curved. The cardinal points and the associated cardinal planes are a set of special points and planes in an optical system which help in the analysis In some cases the detector is made curved; in others flat media is mechanically conformed to the shape of the focal plane through the use of retaining clips or bolts, or by the application of a vacuum. This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. A field flattener, -in its simplest form, a planoconvex lens in direct contact with the film- is sometimes used. Systems with such lens are called Schmidt-Väisälä camera. The Schmidt-Väisälä camera is an astronomical telescopeIntended for wide-field (5 to 10 degrees of arc photographic work
Applications
The Schmidt camera is typically used as a survey instrument, for research programs in which a large amount of sky must be covered. These include astronomical surveys, comet and asteroid searches, and nova patrols. Astronomical surveys generally involve imaging or mapping of regions of the sky using Telescopes. A comet is a small Solar System body that orbits the Sun and when close enough to the Sun exhibits a visible coma (atmosphere or a tail — Asteroids, sometimes called Minor planets or planetoids', are bodies—primarily of the inner Solar System —that are smaller than planets but A nova (pl novae or novas) is a Cataclysmic nuclear explosion caused by the accretion of hydrogen onto the surface of a White
In addition, Schmidt cameras and derivative designs are frequently used for tracking artificial earth satellites. This article is about artificial satellites For natural satellites also known as moons see Natural satellite.
Starting in the early 1970s, Celestron marketed an 8-inch Schmidt Camera. This article is about the Decade 1970-1979 For the Year 1970 see 1970. Celestron is a company that makes and imports Telescopes Binoculars, Spotting scopes Microscopes and accessories for their products The camera was focused in the factory and was made of materials with low expansion coefficients so it would never need to be focused in the field. Early models required the photographer to cut and develop individual frames of 35mm film as the film holder could only hold one frame of film. About 300 Celestron Schmidt Cameras were produced.
The Schmidt system was popular, used in reverse, for television projection systems. A video projector takes a Video signal and projects the corresponding image on a Projection screen using a lens system Large Schmidt projectors were used in theaters but systems as small as 8-inches were made for home use and other small venues.
A Schmidt telescope was at the heart of the Hipparcos satellite from the European Space Agency(1989-1993). Hipparcos (an Acronym for Hi gh P recision Par allax Co llecting S atellite) was an Astrometry mission The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member Year 1989 ( MCMLXXXIX) was a Common year starting on Sunday (link displays 1989 Gregorian calendar) Year 1993 ( MCMXCIII) was a Common year starting on Friday (link will display full 1993 Gregorian calendar) This was used in the Hipparcos Survey which mapped the distances of more than a million stars with unprecedented accuracy - this included 99% of all stars up to magnitude 11. The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value The spherical mirror used in this telescope was extremely accurate; if scaled up to the size of the Atlantic Ocean, bumps on its surface would be about 10 cm high[1]. A centimetre ( American spelling: centimeter, symbol cm) is a unit of Length in the Metric system, equal to one hundredth
Another famous and productive Schmidt camera is the Oschin Schmidt Telescope at Palomar Observatory, which was used in the National Geographic Society - Palomar Observatory Sky Survey (POSS, 1958), the POSS-II survey, the Palomar-Leiden (asteroid) Surveys, and other projects. The Samuel Oschin telescope is a 48-inch (122-m aperture Schmidt camera at the Palomar Observatory in northern San Diego County, California Palomar Observatory is a privately owned Observatory located in San Diego County California, 90 miles (145 Km) Southeast of Mount Wilson The National Geographic Society - Palomar Observatory Sky Survey (NGS-POSS is a major photographic survey of the night sky completed at Palomar Observatory in 1958 The telescope used in the Lowell Observatory Near-Earth-Object Search (LONEOS) is also a Schmidt camera. Lowell Observatory Near-Earth-Object Search (LONEOS was a project designed to discover Asteroids and Comets that orbit near the Earth The Schmidt telescope of the Karl Schwarzschild Observatory is the largest Schmidt camera of the world. The Karl-Schwarzschild-Observatorium ( Karl Schwarzschild Observatory) is an astronomical Observatory owned and operated by the institute of Thüringer
Derivative designs
Lensless Schmidt
Prior to Schmidt's design, the solution to spherical aberration was to place an aperture stop at the center of curvature of the mirror, stopping the aperture to f/10. This removes spherical aberration while preserving the wide field of the short focal-length mirror. However, it does so at the cost of light-gathering ability. Although this solution was well-known long before Bernhard Schmidt invented his corrector plate, the design is is sometimes given the retronym "lensless Schmidt". A retronym is a type of Neologism coined for an old object or concept whose original name has come to be used for something else is no longer unique or is otherwise inappropriate
Schmidt-Väisälä
Prof. The Schmidt-Väisälä camera is an astronomical telescopeIntended for wide-field (5 to 10 degrees of arc photographic work Yrjö Väisälä originally designed an "astronomical camera" similar to Bernhard Schmidt's "Schmidt camera", but the design was unpublished. Väisälä did mention it in lecture notes in 1924 with a footnote: "problematic spherical focal plane". Once Väisälä saw Schmidt's publication, he promptly went ahead and solved the field-flattening problem in Schmidt's design by placing a doubly-convex lens slightly in front of the film holder. This resulting system is known as: Schmidt-Väisälä camera or sometimes as Väisälä camera. The Schmidt-Väisälä camera is an astronomical telescopeIntended for wide-field (5 to 10 degrees of arc photographic work
Baker-Schmidt
In 1940, James Baker of Harvard University modified the Schmidt camera design to include a convex secondary mirror, which reflected light back toward the primary. James Gilbert Baker ( November 11, 1914 &ndash June 29, 2005) was an American Astronomer and Optician. The photographic plate was then installed near the primary, facing the sky. This variant is called the Baker-Schmidt camera.
Baker-Nunn
The Baker-Nunn design, by Dr. Baker and Joseph Nunn, replaced the Baker-Schmidt camera's corrector plate with a small triplet corrector lens closer to the focus of the camera, using 65 mm film. Joseph Nunn (1905&ndash1968 was an American Engineer. In 1956 he worked in collaboration with Dr A dozen f/0. 75 Baker-Nunn cameras with 20-inch aperatures – each weighing 3. 5 tons including a multiple axis mount allowing it to follow satellites in the sky – were used by the Smithsonian Astrophysical Observatory to track artificial satellites from the late 1950s to mid 1970s. The Smithsonian Astrophysical Observatory (SAO is a "research institute" of the Smithsonian Institution headquartered in Cambridge Massachusetts, [2]
Mersenne-Schmidt
The Mersenne-Schmidt camera consists of a concave paraboloidal primary mirror, a convex spherical secondary mirror, and a concave spherical tertiary mirror.
Schmidt-Newtonian
The addition of a flat secondary mirror at 45° to the optical axis of the Schmidt design creates a Schmidt-Newtonian telescope. The optical design of the Schmidt-Newton telescope combines elements from both the Schmidt camera and the Newtonian telescope. A secondary mirror (or secondary) is a second light gathering and focusing surface in a Reflector telescope. The optical design of the Schmidt-Newton telescope combines elements from both the Schmidt camera and the Newtonian telescope.
Schmidt-Cassegrain
The addition of a convex secondary mirror to the Schmidt design directing light through a hole in the primary mirror creates a Schmidt-Cassegrain telescope. The Schmidt-Cassegrain is a Catadioptric Telescope. It combines a folded optical path with a corrector plate to make a compact astronomical instrument The Schmidt-Cassegrain is a Catadioptric Telescope. It combines a folded optical path with a corrector plate to make a compact astronomical instrument
The last two designs are popular with telescope manufacturers because they are compact and use simple spherical optics.
Notes, references
External links
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