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38-681: In 1964 Markarian decided to search for this kind of galaxy. The First Byurakan Survey commenced in 1965 using the Schmidt telescope at the Byurakan Astrophysical Observatory in Armenian SSR. The telescope used a 132 cm mirror and 102 cm correcting plate. When this started it was the largest telescope to have a full aperture objective prism. The purpose of the survey was to find galaxies with an ultraviolet excess. The optics used were corrected for blue violet. Prisms in this had

76-422: 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 the film, plate, or other detector be correspondingly curved. In some cases

114-403: 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

152-546: 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Väisälä originally designed an "astronomical camera" similar to Bernhard Schmidt's "Schmidt camera", but the design was unpublished.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

190-462: A dual lens system of a plano-convex and a plano-concave lens fitted into an eyepiece adaptor which superficially resembles a Barlow lens . Coma of a single lens or a system of lenses can be minimized (and in some cases eliminated) by choosing the curvature of the lens surfaces to match the application. Lenses in which both spherical aberration and coma are minimized at a single wavelength are called bestform or aplanatic lenses . Vertical coma

228-490: A full spectra survey at high galactic latitudes. 1980 saw the completion of plate analysis and picking the objects that would be included. Twelve more papers with objects from the First Byurakan Survey brought the list up to 1500 galaxies. A list titled "First Byurakan Survey" circulated in 1986, including the original 1500 galaxies and 32 extras numbered from 9001 to 9032. In 1989 an extended list numbering up to 1515

266-419: A low dispersion of 180 nm/mm in order not to spread out the galactic core spectrum too much and confuse it with other objects. This permitted classification of galaxies with magnitudes down to 17.5. Seventy galaxies with UV-continuum appeared on lists, and the term "Markarian galaxies" came into use. Two more lists brought the number of galaxies up to 302 in 1969. The FBS continued observations till 1978 with

304-494: 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

342-406: 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

380-473: Is Mrk 20, Mrk 1318 is Mrk 49, and Mrk 890 is Mrk 503. The various objects in this catalogue include Seyfert galaxies , starburst galaxies , H II regions , active galactic nuclei , BL Lac objects and quasars . Some objects are actually giant glowing regions of ionized hydrogen in a galaxy including Mrk 59, 71, 86b, 94, 256b, 404, 489b, 1039, 1236, 1315, and 1379a. Other galaxies have black holes shooting hot gas in energetic jets. Many are variable, showing

418-404: Is a form of chromatic aberration . 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

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456-708: 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

494-545: 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,

532-739: 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 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

570-403: 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

608-487: 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 a wide-field photographic catadioptric telescope ,

646-634: 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

684-405: 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 the center of curvature " C " of the mirrors for

722-535: The Schmidt design directing light through a hole in the primary mirror creates a Schmidt–Cassegrain telescope . The last two designs are popular with telescope manufacturers because they are compact and use simple spherical optics. A short list of notable and/or large aperture Schmidt cameras. Coma (optics) In optics (especially telescopes ), the coma ( / ˈ k oʊ m ə / ), or comatic aberration , in an optical system refers to aberration inherent to certain optical designs or due to imperfection in

760-680: 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)

798-455: The brightness comes from a small region. Schmidt telescope 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 was invented by Bernhard Schmidt in 1930. Some notable examples are the Samuel Oschin telescope (formerly Palomar Schmidt),

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836-409: 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

874-402: 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 is at the center of curvature of the primary mirror in this design

912-404: 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

950-407: 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

988-409: The galaxy core of "s" for star-like or "d" for diffuse was used, with hybrids of "ds" or "sd". A digit 1,2 or 3 indicated strong, moderate or weak UV emission. A letter "e" was appended if emission lines were apparent. Eleven galaxies had a blue star in the foreground creating the ultraviolet excess, so these galaxies do not really fall into the class. Another problem is duplicate entries where Mrk 107

1026-404: The incoming rays strike the mirror at an angle, individual rays are not reflected to the same point. When looking at a point that is not perfectly aligned with the optical axis, some of the incoming light from that point will strike the mirror at an angle. This causes an image that is not in the center of the field to appear as wedge-shaped. The further off-axis (or the greater the angle subtended by

1064-459: 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

1102-416: 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

1140-424: The point with the optical axis), the worse this effect is. This causes stars to appear to have a cometary coma , hence the name. Schemes to reduce coma without introducing spherical aberration include Schmidt , Maksutov , ACF and Ritchey–Chrétien optical systems. Correction lenses, " coma correctors " for Newtonian reflectors have been designed which reduce coma in newtonian telescopes. These work by means of

1178-457: 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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1216-421: 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 is an aspheric lens which corrects

1254-443: 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

1292-666: 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

1330-518: 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

1368-472: 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

1406-501: Was published. In 2005, the " Second Byurakan Survey " (SBS, SBSSS, BSS, MrkII, Markarian II) was carried out, extending the MrkI survey to fainter objects, making a catalogue of 3563 objects of 1863 galaxies (SBSG) and 1700 stars (SBSS); 761 of the galaxies are AGN (155 Seyferts, 596 quasars, 10 blazars). The catalogues of galaxies included a name, coordinates, spectral type, visible size and morphological type of galaxy. A custom designator for

1444-574: 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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