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44-621: The photographs were taken with the 48 inches (1.2 m) Samuel Oschin telescope at Palomar Observatory, and the astronomical survey was funded by a grant from the National Geographic Society to the California Institute of Technology . Among the primary minds behind the project were Edwin Hubble , Milton L. Humason , Walter Baade , Ira Sprague Bowen and Rudolph Minkowski . The first photographic plate

88-407: A blue sensitive Kodak 103a-O plate. This allowed the color of celestial objects to be recorded. The survey was originally meant to cover the sky from the north celestial pole to -24° declination. This figure specifies the position of the plate center, hence the actual coverage under the original plan would have been to approximately -27°. It was expected that 879 plate pairs would be required. However

132-429: A broader spectrum. Between 2000 and 2001, it was converted to use a CCD imager. The corrector plate was recently replaced using glass that is transparent to a wider range of wavelengths. The telescope was originally hand-guided through one of two 10-inch-aperture (0.25 m) refracting telescopes mounted on either side. The camera is now fully automated and remote-controlled. The data collected are transmitted over

176-403: A curve for telescopes of focal ratio f/2.5 or faster. Also, for fast focal ratios, the curve obtained is not sufficiently exact and requires additional hand correction. A third method, invented in 1970 for Celestron by Tom Johnson and John O'rourke, uses a vacuum pan with the correct shape of the curve pre-shaped into the bottom of the pan, called a "master block". The upper exposed surface

220-553: A design was used to construct a working 1/8-scale model of the Palomar Schmidt, with a 5° field. The retronym "lensless Schmidt" has been given to this configuration. 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Väisälä originally designed an "astronomical camera" similar to Bernhard Schmidt's "Schmidt camera", but the design was unpublished.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

264-509: A multiple axis mount allowing it to follow satellites in the sky – were used by the Smithsonian Astrophysical Observatory to track artificial satellites from June 1958 until the mid-1970s. The Mersenne–Schmidt camera consists of a concave paraboloidal primary mirror, a convex spherical secondary mirror, and a concave spherical tertiary mirror. The first two mirrors (a Mersenne configuration) perform

308-463: A wide-field photographic catadioptric telescope , the Schmidt camera. It is now used in several other telescope designs, camera lenses and image projection systems that utilise a spherical primary mirror. Schmidt corrector plates work because they are aspheric lenses with spherical aberration that is equal to but opposite of the spherical primary mirrors they are placed in front of. They are placed at

352-742: Is also a Schmidt camera. The Schmidt telescope of the Karl Schwarzschild Observatory is the largest Schmidt camera of the world. A Schmidt telescope was at the heart of the Hipparcos (1989–1993) satellite from the European Space Agency . This was used in the Hipparcos Survey which mapped the distances of more than a million stars with unprecedented accuracy: it included 99% of all stars up to magnitude 11. The spherical mirror used in this telescope

396-526: Is an aspheric lens which corrects the spherical aberration introduced by the spherical primary mirror of the Schmidt or Schmidt–Cassegrain telescope designs. It was invented by Bernhard Schmidt in 1931, although it may have been independently invented by Finnish astronomer Yrjö Väisälä in 1924 (sometimes called the Schmidt–Väisälä camera as a result). Schmidt originally introduced it as part of

440-450: Is at the center of curvature of the primary mirror in this design the tube length can be very long for a wide-field telescope. There are also the drawbacks of having the obstruction of the film holder or detector mounted at the focus halfway up the tube assembly, a small amount of light is blocked and there is a loss in contrast in the image due to diffraction effects of the obstruction and its support structure. A Schmidt corrector plate

484-545: Is then polished flat creating a corrector with the correct shape once the vacuum is released. This removes the need to have to hold a shape by applying an exact vacuum and allows for the mass production of corrector plates of the same exact shape. The technical difficulties associated with the production of Schmidt corrector plates led some designers, such as Dmitri Dmitrievich Maksutov and Albert Bouwers , to come up with alternative designs using more conventional meniscus corrector lenses. Because of its wide field of view,

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528-701: The Canada–France–Hawaii Telescope . This had a field of view of 7.8 square degrees, and was used for the Palomar Transient Factory . In 2017 the telescope became the host of the Zwicky Transient Facility . Unlike its predecessors, this was custom designed for the Oschin telescope and its wide field of view, using a 16×6144×6160 CCD array (606 megapixels) with a 47 square degree field of view. About half of

572-609: The High Performance Wireless Research and Education Network (HPWREN). It is programmed and operated primarily from Pasadena, California , with no operator on site, except to open and close the observatory dome. The first CCD camera installed was the Near-Earth Asteroid Tracking (NEAT) camera, which had three separate 4k×4k sensors arranged in a north–south line with substantial (1°) gaps between them. The total field of view

616-576: The Ohio State University . This work is commonly found wherever a photographic print edition of the NGS-POSS is held. Many astronomical catalogs are partial derivatives of the NGS-POSS (e.g. Abell Catalog of Planetary Nebulae ), which was used for decades for purposes of cataloging and categorizing celestial objects, especially in studies of galaxy morphology . Innumerable astronomical objects were discovered by astronomers studying

660-610: The Oschin Schmidt , is a 48-inch-aperture (1.22 m) Schmidt camera at the Palomar Observatory in northern San Diego County, California , United States. It consists of a 49.75 inches (1.264 m) Schmidt corrector plate and a 72 inches (1.8 m) (f/2.5) mirror. The instrument is strictly a camera; there is no provision for an eyepiece to look through it. It originally used 10 inches (25 cm) and 14 inches (36 cm) glass photographic plates . Since

704-517: The NGS-POSS photographs. In 1986, work was begun on a digital version of the NGS-POSS. Eight years later, the scanning of the original NGS-POSS plates was completed. The resulting digital images were compressed and published as the Digitized Sky Survey in 1994. The Digitized Sky Survey was made available on a set of 102 CD-ROMs, and can also be queried through several web interfaces. In 1996, an even more compressed version, RealSky ,

748-584: 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. In addition, Schmidt cameras and derivative designs are frequently used for tracking artificial Earth satellites . The first relatively large Schmidt telescopes were built at Hamburg Observatory and Palomar Observatory shortly before World War II . Between 1945 and 1980, about eight more large (1 meter or larger) Schmidt telescopes were built around

792-500: The Survey was ultimately extended to -30° plate centers, giving irregular coverage to as far south as -34° declination, and utilizing 936 total plate pairs. The limiting magnitude of the survey varied depending on the region of the sky, but is commonly quoted as 22nd magnitude on average. The NGS-POSS was published shortly after the Survey was completed as a collection of 1,872 photographic negative prints each measuring 14" x 14". In

836-723: The UK Science Research Council with a 1.2 meter Schmidt telescope at Siding Spring Observatory engaged in a collaborative sky survey to complement the first Palomar Sky Survey, but focusing on the southern hemisphere. The technical improvements developed during this survey encouraged the development of the Second Palomar Observatory Sky Survey (POSS II). The telescope used in the Lowell Observatory Near-Earth-Object Search (LONEOS)

880-455: The center of curvature " C " of the mirrors for a pure Schmidt camera and just behind the prime focus for a Schmidt–Cassegrain . The Schmidt corrector is thicker in the middle and the edge. This corrects the light paths so light reflected from the outer part of the mirror and light reflected from the inner portion of the mirror is brought to the same common focus " F ". The Schmidt corrector only corrects for spherical aberration. It does not change

924-409: The corrector. Schmidt himself worked out a second, more elegant, scheme for producing the complex figure needed for the correcting plate. A thin glass disk with a perfectly polished accurate flat surface on both sides was placed on a heavy rigid metal pan. The top surface of the pan around the edge of the glass disk was ground at a precise angle or bevel based on the coefficient of elasticity of

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968-490: The early 1970s there was another "printing" of the Survey, this time on 14" x17" photographic negative prints. The California Institute of Technology bookstore used to sell prints of selected POSS regions. The regions were chosen to support educational exercises and the set was a curriculum teaching tool. In 1962, the Whiteoak Extension , comprising 100 red-sensitive plates extending coverage to -42° declination,

1012-404: 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 . 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. The photographic plate

1056-411: The film, plate, or other detector be correspondingly curved. 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 . A field flattener , in its simplest form a planoconvex lens in front of the film plate or detector, is sometimes used. Since the corrector plate

1100-407: The focal length of the system. Schmidt corrector plates can be manufactured in many ways. The most basic method, called the "classical approach", involves directly figuring the corrector by grinding and polishing the aspherical shape into a flat glass blank using specially shaped and sized tools. This method requires a high degree of skill and training on the part of the optical engineer creating

1144-516: The focal plane is curved, these plates had to be preformed in a special jig before being loaded into the camera. Construction on the Schmidt telescope began in 1939 and it was completed in 1948. It was named the Samuel Oschin telescope in 1986. Before that it was just called the 48 inches (1.2 m) Schmidt. In the mid-1980s, the corrector plate was replaced using glass with less chromatic aberration , producing higher quality images over

1188-864: The go-ahead, she recruited eleven volunteers from the Mount Wilson Observatory Association (MWOA) and the Los Angeles Astronomical Society (LAAS), and the team then spent 13 weekends (more than one thousand hours) poring over the stacks, placing plates in protective sleeves, and packing them in more than 500 boxes that were transported to Palomar. All of the volunteers were presented with the gift of having asteroids named after them, compliments of Carolyn S. Shoemaker : 10028 Bonus , 12680 Bogdanovich , 13914 Galegant , 16452 Goldfinger , 19173 Virginiaterése , 20007 Marybrown , 21148 Billramsey , 22294 Simmons , 27706 Strogen , and 29133 Vargas . Mueller

1232-616: The large photographic glass plate negatives exposed on the telescope, some 19,000 in all, had been accumulating in the sub-basement of the Robinson building at the California Institute of Technology since 1949. In 2002, astronomer Jean Mueller approached Richard Ellis , the director of the Caltech Optical Observatories , to volunteer to the task of organizing the Oschin Telescope plate archive. Given

1276-459: The object. Starting in the early 1970s, Celestron marketed an 8-inch Schmidt camera. 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 35 mm film, as the film holder could only hold one frame of film. About 300 Celestron Schmidt cameras were produced. The Schmidt system

1320-416: The particular type of glass that was being used. The glass plate was sealed to the ground edge of the pan. Then a vacuum pump was used to exhaust the air between the pan and glass through a small hole in the center of the pan until a particular negative pressure had been achieved. This caused the glass plate to warp slightly. The exposed upper surface of the glass was then ground and polished spherical. When

1364-463: The same function of the correcting plate of the conventional Schmidt. This form was invented by Paul in 1935. A later paper by Baker introduced the Paul-Baker design, a similar configuration but with a flat focal plane. The addition of a flat secondary mirror at 45° to the optical axis of the Schmidt design creates a Schmidt–Newtonian telescope . The addition of a convex secondary mirror to

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1408-443: The vacuum was released, the lower surface of the plate returned to its original flat form while the upper surface had the aspheric figure needed for a Schmidt corrector plate. Schmidt's vacuum figuring method is rarely used today. Holding the shape by constant vacuum is difficult and errors in the o-ring seal and even contamination behind the plate could induce optical errors. The glass plate could also break if bent enough to generate

1452-619: The world. One particularly famous and productive Schmidt camera is the Oschin Schmidt Telescope at Palomar Observatory , completed in 1948. This instrument 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 European Southern Observatory with a 1-meter Schmidt telescope at La Silla and

1496-498: Was 3.75 square degrees. From 2003 to 2007, it was the home of the Quasar Equatorial Survey Team camera. This consisted of 112 CCDs, each 2400×600 pixels (161 megapixels total), arranged in four columns of 28 (with gaps between), the largest CCD mosaic used in an astronomical camera at the time. The next camera installed (in 2009) was a 12,288 by 8,192 pixel mosaic (100 megapixel) originally built for

1540-648: Was also rewarded with a visit to the Keck Observatory in Hawaii . The Oschin Telescope was responsible for the discovery of 90377 Sedna on 2003-11-14 and Eris , the "10th Planet" on 2005-01-05 from images taken 2003-10-21. The peculiar Type Ia supernova SN 2002cx was discovered with the Oschin telescope on 2002-05-12, 21 UT. Other discoveries include 90482 Orcus (in 2004) and 50000 Quaoar (in 2002), both large trans-Neptune objects. In June 2011 it

1584-410: Was completed and published as identically-sized photographic negative prints. The Whiteoak Extension is often found in libraries stored as an appendix or companion to the photographic print edition of the NGS-POSS. This brings the number of prints to 1,972 for most holders of a photographic edition of the NGS-POSS. In 1981, a set of NGS-POSS Transparency Overlay Maps was published by Robert S. Dixon of

1628-407: Was exposed on November 11, 1949. 99% of the plates were taken by June 20, 1956, but the final 1% was not completed until December 10, 1958. The survey utilized 14 inches (36 cm) square photographic plates, covering about 6 ° of sky per side (approximately 36 square degrees per plate). Each region of the sky was photographed twice, once using a red sensitive Kodak 103a-E plate, and once with

1672-525: Was extremely accurate; if scaled up to the size of the Atlantic Ocean , bumps on its surface would be about 10 cm high. The Kepler photometer , mounted on NASA's Kepler space telescope (2009–2018), is the largest Schmidt camera launched into space. In 1977 at Yerkes Observatory , a small Schmidt telescope was used to derive an accurate optical position for the planetary nebula NGC 7027 to allow comparison between photographs and radio maps of

1716-703: Was invented by Bernhard Schmidt in 1930. Some notable examples are the Samuel Oschin telescope (formerly Palomar Schmidt), the UK Schmidt Telescope and the ESO Schmidt; these provided the major source of all-sky photographic imaging from 1950 until 2000, when electronic detectors took over. A recent example is the Kepler space telescope exoplanet finder. Other related designs are the Wright camera and Lurie–Houghton telescope . The Schmidt camera

1760-535: Was invented by Estonian-German optician Bernhard Schmidt in 1930. Its optical components are an easy-to-make spherical primary mirror , and an aspherical correcting lens , known as a Schmidt corrector plate , located at the center of curvature of the primary mirror. 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 . Schmidt cameras have very strongly curved focal planes , thus requiring that

1804-858: Was marketed by the Astronomical Society of the Pacific . in 2001, a catalog identifying over 89 million objects on the NGS-POSS was placed online as part of the Minnesota Automated Plate Scanner Catalog of the POSS I. The catalog was also distributed in a set of 4 DVD-ROMs. The catalog contains accurate sky positions and brightness measurements for all of these objects as well as more esoteric parameters such as ellipticity, position angle, and concentration index. Samuel Oschin telescope The Samuel Oschin telescope ( / ˈ ɔː ʃ ɪ n / ), also called

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1848-476: Was popular, used in reverse, for television projection systems, notably the Advent design by Henry Kloss . Large Schmidt projectors were used in theaters, but systems as small as 8 inches were made for home use and other small venues. In the 1930s, Schmidt noted that the corrector plate could be replaced with a simple aperture at the mirror's center of curvature for a slow (numerically high f-ratio) camera. Such

1892-450: Was reported the telescope discovered 6 supernovae located 8 billion light years from Earth whose composition lacks hydrogen. This is different from normal supernovae, and will contribute to the research of star formation. Schmidt camera A Schmidt camera , also referred to as the Schmidt telescope , is a catadioptric astrophotographic telescope designed to provide wide fields of view with limited aberrations . The design

1936-587: Was then installed near the primary, facing the sky. This variant is called the Baker-Schmidt camera. The Baker–Nunn design, by Baker and Joseph Nunn , replaces the Baker-Schmidt camera's corrector plate with a small triplet corrector lens closer to the focus of the camera. It used a 55 mm wide film derived from the Cinemascope 55 motion picture process. A dozen f/0.75 Baker-Nunn cameras with 20-inch apertures – each weighing 3.5 tons including

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