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Consumer version of this design typically achieve focus by adjusting the position of the primary mirror rather than a traditional eye-piece. This means that small changes in the position of the mirror are magnified by the focal length of the telescope. As the mirror is not permanently fixed in place,
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One very well-corrected type of non-compact design is the concentric (or monocentric) Schmidt–Cassegrain, where all the mirror surfaces and the focal surface are concentric to a single point: the center of curvature of the primary. Optically, non-compact designs give better aberration correction and
265:, or one of each), they can be divided into two principal types: compact and non-compact. In the compact form, the corrector plate is located at or near the focus of the primary mirror. In the non-compact, the corrector plate remains at or near the center of curvature (twice the
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it is possible for it to move by a small amount and cause the image to shift. This is otherwise known as "mirror flop". Some
Schmidt-Cassegrain telescopes are equipped with mirror locks to fix the primary mirror in place once focus has been achieved.
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Compact designs combine a fast primary mirror and a small, strongly curved secondary. This yields a very short tube length, at the expense of field curvature. Compact designs have a primary mirror with a
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located behind the primary. Some designs include additional optical elements (such as field flatteners) near the focal plane. The first large telescope to use the design was the
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of around f/2 and a secondary with a focal ratio also around f/2, the separation of the two mirrors determining a typical system focal ratio around f/10.
493:. The Society for Astronomical Sciences 25th Annual Symposium on Telescope Science. Big Bear, Calif.: Society for Astronomical Sciences. p. 191.
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is also recognized as the largest
Schmidt-Cassegrain. The telescope is noted for its large field of view, up 60 times a full moon.
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The
Schmidt–Cassegrain design is very popular with consumer telescope manufacturers because it combines easy-to-manufacture
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manufactured the first one during World War II as part of their research into optical designs for the military. As in the
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means they are not a wide-field telescope like their
Schmidt camera predecessor, but they are good for more narrow-field
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While there are many variations of the
Schmidt–Cassegrain telescope design (both mirrors spherical, both mirrors
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a flatter field than most compact designs, but at the expense of longer tube length.
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People demonstrating a
Schmidt–Cassegrain telescope at a sidewalk gathering
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optical surfaces to create an instrument with the long focal length of a
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420:. Vol. 2, Part 2. Cambridge University Press. 1984. p. 177.
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View of the corrector and primary mirror of a
Schmidt–Cassegrain.
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432:"The Mount Wilson Optical Shop During the Second World War"
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to make a compact astronomical instrument that uses simple
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Magnet Loader for
Schmidt-Cassegrain Mirror Flop Reduction
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Linfoot, E.H. (1956). "Colloquium on
Schmidt optics".
434:, American Astronomical Society Meeting 205, #02.01;
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60:. Unsourced material may be challenged and removed.
453:"A short history of Scotland's largest telescope"
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501:– via SAO/NASA Astrophysics Data System.
476:V. Sacek, Telescope-Optics.net page 10.2.2.4.2
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436:Bulletin of the American Astronomical Society
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230:and relays the image through the perforated
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487:Vander Haagen, G.A. (23 May 2006).
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418:The General History of Astronomy
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451:Dvinsky, Dalcash (2018-04-05).
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69:"Schmidt–Cassegrain telescope"
27:Type of catadioptric telescope
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522:Schmidt-Cassegrain telescopes
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192:in 1940. The optical shop at
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305:with the lower cost per
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194:Mount Wilson Observatory
345:List of telescope types
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524:at Wikimedia Commons
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499:2006SASS...25..191V
438:, Vol. 36, p. 1339.
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355:Newtonian telescope
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178:James Gilbert Baker
350:Maksutov telescope
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399:: 170–177.
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376:References
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215:. In this
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