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Topic: Schmidt corrector plate

	Sky-Watcher Telescope. How does a telescope work?
		Schmidt-Cassegrain telescopes use a thin aspherical corrector plate, which is a lens carefully matched to the primary concave mirror to correct for spherical aberration.
		Parallel light rays enter the telescope through the corrector plate and are then reflected by the primary mirror to a convex secondary mirror which is mounted inside the focal point and concentric with the corrector plate.
		Light enters through the concave side of the corrector plate and the primary mirror reflects it back up the tube to the secondary which is often a mirrored spot on the convex side of the corrector plate.
	www.skywatchertelescope.com /EducationTBOD.html (1247 words)

	Schmidt camera
		This same wavefront modification is accomplished with the Schmidt corrector with the neutral zone at 0.707 of the radius.
		being the corrector radius of curvature, b and b' the third- and fifth-order aspheric coefficient (for the ray aberration; fourth- and sixth-order for the wavefront), and n' the index of refraction of the exit media (media to the right of the Schmidt surface, normally air, with n'=1).
		While corrector with the 0.866 radius neutral zone brings the circles of least confusion for all wavelengths to a common focus (left), corrector with the neutral zone at 0.707 of the radius, brings diffraction (best) foci for all wavelengths to a common focus.
	www.telescope-optics.net /Schmidt-camera.htm (1716 words)

	Bernard Schmidt - His Camera and Its Derivatives - By Mark Christensen, Ph.D.
		The key concept behind the Schmidt Camera is the use of a spherical mirror (the easiest shape to make), arranged symmetrically so as to avoid off axis aberrations, together with an aspheric (that is, non-spherical) corrector plate, whose function is to eliminate the residual spherical aberration of the mirror.
		Schmidt's solution was to introduce a plate (called variously a Schmidt corrector or a Schmidt plate) in front of the mirror.
		This plate has a gentle curve ground into it designed expressly to bend the rays precisely the amount needed to bring the rays from the various (radial) zones of the mirror to a single focus.
	www.fvastro.org /articles/schmidtp2.htm (1652 words)

	esp@cenet visualizar la descripción
		An oversize but otherwise finished Schmidt corrector plate to be duplicated which is flat on one side and figured on the other is apertured at the optical center thereof and shallow grooves ground into the corrector on the curve side.
		The corrector plate is placed flat side to flat spindle master surface and a thin piece of glass to constitute a replica piece is placed on the corrector plate with a vacuum drawn therebetween to conform their surfaces.
		The corrector plate and replica piece are then removed from the spindle master and the replica piece alone placed flat side to flat surface of the spindle master in optical contact in a semi-permanent bond therewith and constituting together a contour block master.
	v3.espacenet.com /textdes?CY=es&LG=es&DB=EPODOC&IDX=US3837124&DOC=dcb65d04ab6524de9c540dc89048efbf66&QPN=US3837124 (2022 words)

	Schmidt Corrector Mathematics
		In the normal method of making a Schmidt corrector plate, a vacuum is pulled on the back side of the disk until the center deflection of the plate is Zc.
		Equations (7) are used to determine the amount of center deflection, Zc, of the plate under vacuum, and the sagitta, S, of the spherical tool used to grind the plate.
		In this case, the corrector plate is characterized by a relative power, g, and the location of the neutral zone, D, which is given as a fraction of the radius of the corrector plate, i.e., if the neutral zone is at 85%, then D=0.85.
	www.considine.net /drowesmi/vacmath/schmath2.htm (1298 words)

	Spartanburg SC \| GoUpstate.com \| Spartanburg Herald-Journal (Site not responding. Last check: 2007-10-23)
		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.
		Schmidt cameras have very strongly curved focal planes, thus requiring that the film, plate, or other detector be correspondingly curved.
		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.
	www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=Schmidt_telescope (745 words)

	National Park Service: Astronomy and Astrophysics (Palomar 48-inch Oschin (Schmidt) Telescope)
		[4] Schmidt's solution was to design a telescope that used a spherical mirror with a "corrector plate," a lens that could be placed at the center of curvature of the sphere and through which the light would pass.
		The corrector plate lens is thickest in the center, less thick at the edges and least thick between the edges and the center.
		Schmidt designed the plate to refract the light passing through it in such a way as to make up for the spherical aberration introduced by the mirror, without introducing visual errors such as chromatic aberrations commonly found in large reflectors.
	www.cr.nps.gov /history/online_books/butowsky5/astro4f.htm (1472 words)

	[No title]
		For a Schmidt 30x30-degree camera, the fraction of obscured light is approximately 33%, compared to approximately 15% for a 15x15-degree field of view.) The required unobscured collecting area was calculated using known fluorescence fluxes, expected background light, expected optical and photosensor efficiencies, etc.
		In the case of a Schmidt corrector plate, the filter could be bonded to the one-sided lens.
		The corrector plate can be added to the reference design when and if it has been demonstrated to improve performance reliably and at reasonable cost.
	www.physics.utah.edu /~sommers/hybrid/correspondence/optics_memo.html (3082 words)

	Schmidt camera
		A type of photographic telescope that uses a spheroidal primary mirror with a corrector plate at its center of curvature to eliminate spherical aberration; it is named after its inventor, the Estonian-born instrument-maker Bernhard Schmidt (1879-1935).
		Schmidt cameras address a weakness of reflecting telescopes that are based on parabolic mirrors, namely, which is that the accurate focusing only occurs for light falling on the center of the paraboloid.
		A Baker-Schmidt telescope is a modified type of Schmidt camera designed, by James Baker (1914-) of Harvard in 1940, to produce an image free of astigmatism and coma.
	www.daviddarling.info /encyclopedia/S/Schmidt_camera.html (330 words)

	Strapdown stellar sensor and holographic multiple field of view telescope therefor - Patent 5206499
		Also disclosed is a Schmidt telescope embodiment of the invention having a concave spherical mirror and a corrector plate positioned at a center of curvature of the spherical mirror.
		The corrector plate is positioned at the center of curvature (R) of the mirror and corrects for the spherical aberration of the mirror.
		Radiation, corrected by the corrector plate 186, reflects from the spherical mirror 192 to fold mirror 188b, and from fold mirror 188b is directed through an aperture 190 within fold mirror 188a and is focussed upon a detector 194.
	www.freepatentsonline.com /5206499.html (9875 words)

	mirror, focal, focus, light, reflector, field, optical, corrector, Schmidt, mirrors, curvature, large, while - ...
		The spherical aberration is overcome by using a corrector lens in front of the telescope at the radius of the curvature of the mirror.
		The plate is figured by placing a vacuum on one side, and grinding the exact correction required to correct the spherical aberration caused by the primary mirror.
		The corrector, which is thicker in the middle and the edges, corrects the light paths so that the outer and inner parts of the mirror focus at the same distance.
	www.alphasearch.org /Reflecting-telescope.html (2156 words)

	Reflecting telescope at AllExperts
		The spherical aberration is overcome by using a corrector lens in front of the telescope at the radius of the curvature of the mirror.
		The plate is figured by placing a vacuum on one side, and grinding the exact correction required to correct the spherical aberration caused by the primary mirror.
		The corrector, which is thicker in the middle and the edges, corrects the light paths so that the outer and inner parts of the mirror focus at the same distance.
	en.allexperts.com /e/r/re/reflecting_telescope.htm (2124 words)

	Schmidt camera at AllExperts
		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.
		Schmidt cameras have very strongly curved focal planes, thus requiring that the film, plate, or other detector be correspondingly curved.
		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.
	en.allexperts.com /e/s/sc/schmidt_camera.htm (666 words)

	Newsworthy Articles
		The vacuum technique was successfully used because the corrector was made from fused silica which is considerably stronger than crown, the correction was divided between the two sides, and special procedures were incorporated in the processing of the blank.
		The corrector plate was null tested in double pass by placing the corrector very close to an accurate concave spherical mirror.
		The corrector plate is close to the focus requiring a smooth figure, but the overall correction is not very critical.
	www.dfmengineering.com /news_naval_obsrv.html (1506 words)

	PDR material for FD reviewers
		Corrector plate This design exploits the possibility of reducing the spherical aberration, which is not eliminated by the diaphragm, by putting a corrector plate at the center of curvature of the mirror, turning the FD into a true Schmidt camera.
		This approach can be reversed and the use of a corrector plate is then seen as a way of increasing the diaphragm aperture while keeping the spot size under control, thereby increasing the effective light collection area of the detector, which increases the S/N ratio.
		Like the other Schmidt corrector plates, it remains to be demonstrated that it is practical to incorporate such a lens in a camera of this large size that must operate for many years.
	www.physics.utah.edu /~sommers/hybrid/reviews/pdr_materials.html (12784 words)

	Exhibits: Astronomy in California 1850-1950
		Schmidt's life is as interesting as the novel optical system he introduced.
		The camera he introduced, generally referred to as the basic "Schmidt Camera," consists of a concave spherical mirror in front of which is a thin and optically weak corrector plate.
		The Survey was completed in 1959 and copies of the photographic plates (taken in both red and blue light) have been used worldwide for research and discovery.
	www.chabotspace.org /vsc/exhibits/califastronomy/schmidtcamera.asp (562 words)

	Celestron Telescopes -- Product Support
		A: The outside of the corrector plate can be cleaned using a solution of 60% distilled water and 40% isopropyl alcohol with one drop of clear liquid dish soap per quart of solution.
		The solution is applied to a soft tissue or cotton ball and is carefully rubbed onto the corrector plate using radial strokes from the secondary mirror housing outward.
		The corrector plate is optically matched to the mirrors in alignment and in rotation.
	www.celestron.com /support/faq.htm (1337 words)

	The Celestron/Epoch Schmidt Camera
		First, a corrector plate, a thin zero-power aspheric lens, is placed at the radius of curvature of the primary mirror.
		When the pressure plate is clamped against the open frame of the film holder, it curves the photographic emulsion to conform to the Schmidt camera's curved focal plane.
		A Schmidt camera on the other hand will be free of vignetting if the mirror size is equal to the diameter of the corrector plate plus twice the width of the film holder.
	www.robertreeves.com /repair.htm (1811 words)

	spacegazer - Cassegrains (Site not responding. Last check: 2007-10-23)
		This plate reduces the field curvature at the focal plane and physically closes the tube so that air turbulence and dust gathering is eliminated.
		Schmidt Cassegrains are becoming more and more popular and are the most common form of Cassegrain reflector on the market.
		A close brother of the Schmidt Cassegrain is the Maksutov Cassegrain scope which also incorporates a corrector plate, but one of a simpler design, but thicker and therefore heavier.
	www.spacegazer.com /cassegrains-g.asp (710 words)

	Reference.com/Encyclopedia/Schmidt-Cassegrain telescope
		As in the Schmidt camera this design uses a spherical primary mirror and a Schmidt corrector plate to correct for spherical aberration.
		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 focal length) of the primary mirror.
	www.reference.com /browse/wiki/Schmidt-Cassegrain_telescope (497 words)

	Lake County Astronomical Society NightTimes
		The SCT corrector is a shallow, complex curve; the MCT corrector is a deep-dish meniscus.
		An MCT corrector is a spherical meniscus lens, meaning that both the front side and the back side are curved in the same direction, resulting in a concave front and a convex back.
		In comparison, SCT corrector plates, with their weird curve, are difficult to shape correctly and next to impossible to polish to maximum smoothness.
	www.bpccs.com /lcas/Articles/schmidt-cassegrain_and_maksutov-cassegrain.htm (1319 words)

	Optics Demounting Procedure
		Unscrew the 6 or 8 screws surrounding the Schmidt corrector lens.
		The secondary mirror is mounted in the plastic or aluminum fl cell in the center of the corrector lens.
		When returning the corrector lens to the telescope, align the corrector lens serial number with the index mark you made on the tube and return each shim to its proper position.
	www.modelstation.com /rich/demount.htm (534 words)

	Epinions.com - Rich's Telescope Primer Part 1
		In this case, the Schmidt corrector is used to overcome the problems Newtonians face at extremely low focal ratios, and thus these telescopes operate at very short focal ratios of around f/3.6.
		The Maksutov Cassagrain Reflector (MAK) is a somewhat similar instrument to the SCT concept in that it uses a corrector plate at the front of the telescope to bend the light path to come to a focus from spherical secondary.
		This mirror is produced by mirroring a dot on the center of the corrector and is visible from the outside, and yields an essentially collimation-free telescope.
	www.epinions.com /elec-review-C0D-504D19B-39CA3E80-prod5 (5199 words)

	A Glossary for Telescope Buyers and Users
		Common Cassegrain systems include the Schmidt-Cassegrain, in which a corrector plate which appears flat to the unaided eye is mounted just skyward of the secondary mirror, and several varieties of Maksutov-Cassegrain, in which a correcting lens that resembles a thick watch glass is similarly mounted.
		To the naked eye, a Schmidt corrector plate looks like a flat piece of glass, but its surface is actually figured in a subtle manner, to affect the spherical aberration of the system in which it is used.
		A Cassegrain configuration telescope whose optics consist of a concave primary mirror, which is spherical in most of the common commercial designs, a full-aperture Schmidt corrector plate mounted near the focal point of the mirror, and a small, convex secondary mirror positioned in the converging beam, as in a true Cassegrain.
	observers.org /beginner/glossary.html (11783 words)

	[No title]
		Corrector plate is 9 1/16 inch diameter, 11/64 inch thick at edge, with a red alignment mark on the edge.
		A Baker corrector lens for prime focus astrophotography yields a 7 degree field, but requires the primary be stopped down to 20 inches, using a built in aperture ring in the mirror cover.
		The plates revealed the solar corona extending 2 1/2 degrees from the sun, and so impressed Edward Holden of Lick Observatory that he purchased the lens, which was used after July 1889 by E.E. Barnard for photography of comets and the Milky Way.
	www.europa.com /~telscope/tsus.txt (15693 words)

	Astronomy - Buying a telescope - Michael E. Bakich
		The use of a "coma corrector," for scopes with focal ratios of 5 and shorter increases the usable field of view significantly.
		The Schmidt telescope had a spherical primary mirror at the back of the telescope, and a glass corrector plate in the front of the telescope to remove spherical aberration.
		This combination of the Cassegrainian telescope with the Schmidt corrector plate was invented in the 1960s.
	www.astronomy.com /asy/default.aspx?c=ss&id=9 (3237 words)

	Fighting off Dew and Ice
		By radiating heat to the night sky, the corrector plate of a Schmidt-Cassegrain-Telescope is lowering its own temperature.
		The corrector plate of the C-11 is in good thermal contact with the tubus, allowing a heat current to flow from a warmed up outside to the glass.
		On the left side the heaters for the Schmidt corrector plate and the finderscope will be plugged in.
	www.tfh-berlin.de /~goerlich/Tau_e.html (1122 words)

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