229:
236:
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160:, 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 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
39:
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625:, 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 a multiple axis mount allowing it to follow satellites in the sky – were used by the
31:
559:
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Bernhard Schmidt's "Schmidt camera", but the design was unpublished.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
296:
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 the vacuum was
301:
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
283:
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
637:
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 the same function of the correcting plate of the conventional Schmidt. This form was
313:
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 is then polished flat creating a corrector with the correct shape once the vacuum is released. This removes the need to
508:
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
537:
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 a design was used to construct a working 1/8-scale model of the
Palomar Schmidt, with a 5° field. The
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438:
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
152:, thus requiring that 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
584:
modified the
Schmidt camera design to include a convex secondary mirror, which reflected light back toward the primary. The photographic plate was then installed near the primary, facing the sky. This variant is called the Baker-Schmidt camera.
260:. 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 "
251:
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
420:
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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
46:
was originally equipped with photographic film, and an engineer is here showing the film-box, which was then placed behind the locker at the center of the telescope (at the telescope's prime focus)
501:, 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 the object.
365:
Because of its wide field of view, 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
133:, 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
176:
Exaggerated cross section of a
Schmidt corrector plate. The real curves are hard to detect visually, giving the corrector plate the appearance of being an optically flat window.
1077:, Johnson, Thomas J. & O'rourke, John F., "Method for Making Replica Contour Block Masters for Producing Schmidt Corrector Plates", issued 1974-09-24
91:
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
470:. 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
220:, the Schmidt camera. It is now used in several other telescope designs, camera lenses and image projection systems that utilise a spherical primary mirror.
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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:
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invented by Paul in 1935. A later paper by Baker introduced the Paul-Baker design, a similar configuration but with a flat focal plane.
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Schmidt corrector plates can be manufactured in many ways. The most basic method, called the "classical approach", involves directly
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1197:. Presented at the IAU Colloq. 148: The Future Utilisation of Schmidt Telescopes. Vol. 84. Bandung; Indonesia: ASP. p. 8.
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f/2.5 or faster. Also, for fast focal ratios, the curve obtained is not sufficiently exact and requires additional hand correction.
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524:. Large Schmidt projectors were used in theaters, but systems as small as 8 inches were made for home use and other small venues.
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have to hold a shape by applying an exact vacuum and allows for the mass production of corrector plates of the same exact shape.
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The addition of a convex secondary mirror to the Schmidt design directing light through a hole in the primary mirror creates a
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Carter, B. D.; Ashley, M. C. B.; Sun, Y.-S.; Storey, J. W. V. (1992). "Redesigning a Baker-Nunn camera for CCD imaging".
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The last two designs are popular with telescope manufacturers because they are compact and use simple spherical optics.
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of the particular type of glass that was being used. The glass plate was sealed to the ground edge of the pan. Then a
235:
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609:
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John F. Gills, Ph.D, From James Gregory to John Gregory - The 300 Year Evolution of the Maksutov-Cassegrain Telescope
408:. Between 1945 and 1980, about eight more large (1 meter or larger) Schmidt telescopes were built around the world.
264:". The Schmidt corrector only corrects for spherical aberration. It does not change the focal length of the system.
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The technical difficulties associated with the production of Schmidt corrector plates led some designers, such as
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released, the lower surface of the plate returned to its original flat form while the upper surface had the
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Wright, Franklin B. (1959). "Theory and Design of Aplanatic Reflectors Employing a Correcting Lens". In
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Wright, Franklin B. (1959). "Theory and Design of Aplanatic Reflectors Employing a Correcting Lens". In
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11. The spherical mirror used in this telescope was extremely accurate; if scaled up to the size of the
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43:
1649:"From Satellite Tracking to Space Situational Awareness: The USAF and Space Surveillance: 1957 to 2007"
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In addition, Schmidt cameras and derivative designs are frequently used for tracking artificial Earth
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ESO: "National and Project Telescopes at ESO's La Silla Observatory" (accessed November 12, 2010)
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423:(POSS, 1958), the POSS-II survey, the Palomar-Leiden (asteroid) Surveys, and other projects.
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ast.cam.ac.uk (The Institute of Astronomy (IoA), at the University of Cambridge (UoC)) –
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could only hold one frame of film. About 300 Celestron Schmidt cameras were produced.
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as a result). Schmidt originally introduced it as part of a wide-field photographic
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Cannon, R. D. (7–11 March 1994). Jessica Chapman; Russell Cannon; Sandra Harrison;
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1125:
Everhart, Edgar (May 1966), "Making Corrector Plates by Schmidt's Vacuum Method",
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256:" of the mirrors for a pure Schmidt camera and just behind the prime focus for a
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in 1931, although it may have been independently invented by Finnish astronomer
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Rod Mollise, Down with Love, uncle-rods.blogspot.com, Sunday, February 21, 2010
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telescopeѲptics.net, 10.2.2. - Full-aperture Schmidt corrector: Schmidt camera
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Hodges, Paul C. (January 1948), "Bernhard Schmidt and his Reflector Camera",
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30:
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M. Paul (May 1935). "Systèmes correcteurs pour réflecteurs astronomiques".
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Baker, J.G. (1969). "On improving the effectiveness of large telescopes".
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Fawdon, P.; Gavin, M. V. (December 1989), "A Lensless Schmidt Camera",
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1278:"Astrometry with a small Schmidt telescope - The position of NGC 7027"
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to track artificial satellites from June 1958 until the mid-1970s.
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243:) and a spherical mirror combined with a Schmidt corrector plate (
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489:(2009–2018), is the largest Schmidt camera launched into space.
450:(LONEOS) is also a Schmidt camera. The Schmidt telescope of the
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A short list of notable and/or large aperture Schmidt cameras.
325:, to come up with alternative designs using more conventional
411:
One particularly famous and productive Schmidt camera is the
421:
National Geographic Society – Palomar Observatory Sky Survey
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The first relatively large Schmidt telescopes were built at
239:
Example of an optical system using just a spherical mirror (
114:
The Schmidt camera was invented by Estonian-German optician
656:
at 45° to the optical axis of the Schmidt design creates a
1327:"Three new ways to low-cost, super-bright giant-screen TV"
605:
cameras used by the Smithsonian satellite-tracking program
1557:"Paul-Baker and other three-mirror anastigmatic aplanats"
542:"lensless Schmidt" has been given to this configuration.
1109:
The American Journal of Roentgenology and Radium Therapy
1282:
Publications of the Astronomical Society of the Pacific
478:, bumps on its surface would be about 10 cm high.
419:, completed in 1948. This instrument was used in the
164:
effects of the obstruction and its support structure.
1692:
Jim Schwilling "Baker-Nunn Satellite Tracking Camera"
1514:
IEEE Transactions on Aerospace and Electronic Systems
1216:
Pratt, N. M. (1977). "The COSMOS measuring machine".
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Tammy Plotner, universetoday.com, Celestron Telescope
512:
The Schmidt system was popular, used in reverse, for
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in 1930. Its optical components are an easy-to-make
1195:Schmidt Telescopes: Their Past, Present and Future
1601:"Kvistaberg Observatory: The Schmidt Telescope"
1348:Journal of the British Astronomical Association
694:
8:
462:A Schmidt telescope was at the heart of the
454:is the largest Schmidt camera of the world.
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1067:
1065:
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615:Baker-Nunn satellite tracking camera in use
448:Lowell Observatory Near-Earth-Object Search
361:is the largest Schmidt camera in the world.
1495:Revue d'Optique Théorique et Instrumentale
1464:"SeeSat-L Nov-96 : Baker-Nunn Camera"
148:Schmidt cameras have very strongly curved
1681:- includes Baker-Nunn satellite tracking
1301:
42:The 77 cm Schmidt-telescope from 1966 at
695:
692:
608:
171:
907:
1668:
1607:from the original on 21 September 2014
697:Selected Large Schmidt Cameras by Year
284:disk was ground at a precise angle or
204:telescope designs. It was invented by
1276:Cudworth, K. M.; Oravecz, M. (1978).
1091:
1089:
627:Smithsonian Astrophysical Observatory
441:Second Palomar Observatory Sky Survey
309:A third method, invented in 1970 for
7:
1581:from the original on 3 December 2013
980:"Obstruction" in optical instruments
621:The Baker–Nunn design, by Baker and
430:with a 1-meter Schmidt telescope at
1658:. U.S. Air Force Historical Society
1647:Sturdevant, Rick W. (Winter 2008).
1452:, Chapter 9, "The Tracking Systems"
302:generate a curve for telescopes of
25:
1474:from the original on 4 March 2016
1374:Astronomical Society of Australia
1034:Amateur Telescope Making Advanced
936:Amateur Telescope Making Advanced
1563:from the original on 2013-06-17.
87:(formerly Palomar Schmidt), the
1258:from the original on 2008-09-13
466:(1989–1993) satellite from the
345:Alfred Jensch Telescope at the
125:, and an aspherical correcting
773:Karl Schwarzschild Observatory
452:Karl Schwarzschild Observatory
347:Karl Schwarzschild Observatory
212:in 1924 (sometimes called the
98:Other related designs are the
83:Some notable examples are the
76:. The design was invented by
1:
1675:: CS1 maint: date and year (
504:Starting in the early 1970s,
428:European Southern Observatory
1575:"2m-Alfred-Jensch-Telescope"
1238:10.1016/0083-6656(77)90001-0
955:"Telescope Optics – Schmidt"
676:Schmidt–Cassegrain telescope
670:Schmidt–Cassegrain telescope
192:introduced by the spherical
658:Schmidt–Newtonian telescope
648:Schmidt–Newtonian telescope
319:Dmitri Dmitrievich Maksutov
27:Astrophotographic telescope
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645:
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446:The telescope used in the
54:, also referred to as the
1631:November 2, 2010, at the
1394:10.1017/S1323358000019305
998:Malacara, Daniel (1994).
849:Siding Spring Observatory
290:coefficient of elasticity
68:designed to provide wide
34:Diagram of Schmidt camera
18:Burrell Schmidt telescope
1534:10.1109/TAES.1969.309914
815:Largest in Scandinavia
799:at Piszkéstető, Hungary
436:Science Research Council
413:Oschin Schmidt Telescope
280:creating the corrector.
104:Lurie–Houghton telescope
1000:Handbook of Lens Design
882:List of telescope types
746:Samuel Oschin telescope
728:first in North America
685:List of Schmidt cameras
652:The addition of a flat
182:Schmidt corrector plate
168:Schmidt corrector plate
131:Schmidt corrector plate
85:Samuel Oschin telescope
805:Kvistaberg Observatory
765:Calar Alto Observatory
618:
606:
562:Schmidt–Väisälä camera
552:Schmidt–Väisälä camera
487:Kepler space telescope
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248:
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218:catadioptric telescope
214:Schmidt–Väisälä camera
177:
93:Kepler space telescope
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35:
1325:C.P. Gilmore (1979),
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516:systems, notably the
514:television projection
468:European Space Agency
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44:Brorfelde Observatory
41:
33:
1520:(2). IEEE: 261–272.
1470:. 12 November 1996.
1252:"Hipparcos overview"
903:Notes and references
837:UK Schmidt Telescope
821:La Silla Observatory
485:, mounted on NASA's
367:astronomical surveys
190:spherical aberration
137:, while controlling
110:Invention and design
89:UK Schmidt Telescope
1722:Estonian inventions
1526:1969ITAES...5..261B
1450:Vanguard: A History
1386:1992PASA...10...74C
1360:1989JBAA...99..292F
1294:1978PASP...90..333C
1230:1977VA.....21....1P
1218:Vistas in Astronomy
1203:1995ASPC...84....8C
1147:10.1364/AO.5.000713
1139:1966ApOpt...5..713E
1041:. pp. 401–409.
1039:Scientific American
1004:Marcel Dekker, Inc.
943:. pp. 401–409.
941:Scientific American
789:Konkoly Observatory
753:Hamburg Observatory
734:Palomar Observatory
718:Palomar Observatory
417:Palomar Observatory
402:Palomar Observatory
398:Hamburg Observatory
188:which corrects the
1712:Optical telescopes
1029:Ingalls, Albert G.
985:2010-06-20 at the
961:on 20 October 2009
931:Ingalls, Albert G.
917:The Schmidt Camera
892:Meniscus corrector
887:Maksutov telescope
664:Schmidt–Cassegrain
619:
607:
582:Harvard University
528:Derivative designs
499:Yerkes Observatory
493:Other applications
363:
327:meniscus corrector
258:Schmidt–Cassegrain
249:
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202:Schmidt–Cassegrain
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95:exoplanet finder.
48:
36:
1656:Air Power History
872:
871:
868:Largest in space
783:Largest aperture
483:Kepler photometer
63:astrophotographic
56:Schmidt telescope
16:(Redirected from
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633:Mersenne–Schmidt
564:or sometimes as
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278:optical engineer
206:Bernhard Schmidt
116:Bernhard Schmidt
78:Bernhard Schmidt
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72:with limited
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1655:
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1432:. Retrieved
1428:the original
1418:
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959:the original
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557:Yrjö Väisälä
555:
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496:
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461:
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406:World War II
395:
392:Ground-based
383:
364:
341:The 2 meter
333:Applications
316:
308:
282:
271:
261:
253:
250:
244:
240:
210:Yrjö Väisälä
181:
179:
150:focal planes
147:
135:focal ratios
113:
97:
82:
60:catadioptric
55:
51:
49:
1224:(1): 1–42.
841:120 cm
825:100 cm
809:100 cm
777:134 cm
738:122 cm
703:Observatory
623:Joseph Nunn
597:One of the
578:James Baker
522:Henry Kloss
497:In 1977 at
458:Space-based
443:(POSS II).
434:and the UK
304:focal ratio
294:vacuum pump
268:Manufacture
162:diffraction
143:astigmatism
74:aberrations
1701:Categories
1662:2021-06-23
1434:2006-05-15
1262:2011-03-02
862:95 cm
859:photometer
793:60 cm
757:80 cm
722:46 cm
589:Baker–Nunn
520:design by
386:satellites
351:Tautenburg
1611:1 October
1585:1 October
1410:118433981
1402:0066-9997
1380:(1): 74.
1312:122376141
965:1 October
763:Moved to
576:In 1940,
506:Celestron
472:magnitude
464:Hipparcos
381:patrols.
355:Thuringia
311:Celestron
120:spherical
80:in 1930.
66:telescope
1629:Archived
1605:Archived
1579:Archived
1561:Archived
1542:51647158
1478:23 April
1472:Archived
1468:SeeSat-L
1256:Archived
1193:(eds.).
1155:20048933
983:Archived
876:See also
767:in 1974
706:Aperture
540:retronym
432:La Silla
375:asteroid
343:diameter
329:lenses.
299:aspheric
274:figuring
224:Function
1522:Bibcode
1382:Bibcode
1356:Bibcode
1290:Bibcode
1288:: 333.
1226:Bibcode
1199:Bibcode
1135:Bibcode
1075:3837124
1031:(ed.).
933:(ed.).
709:Year(s)
359:Germany
198:Schmidt
196:of the
58:, is a
1540:
1448:NASA,
1408:
1400:
1310:
1153:
1081:
1010:
857:Kepler
518:Advent
245:bottom
184:is an
154:vacuum
1652:(PDF)
1538:S2CID
1406:S2CID
1308:S2CID
712:Note
599:Baker
371:comet
286:bevel
1677:link
1613:2014
1587:2014
1480:2018
1398:ISSN
1151:PMID
1008:ISBN
967:2014
865:2009
844:1973
831:ESO
828:1971
812:1963
796:1962
780:1960
760:1954
744:the
741:1948
725:1936
603:Nunn
481:The
426:The
400:and
379:nova
373:and
321:and
156:. A
141:and
139:coma
127:lens
102:and
1530:doi
1390:doi
1298:doi
1234:doi
1143:doi
847:At
580:of
415:at
349:in
241:top
200:or
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601:–
262:F
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