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Topic: Cassegrain telescope

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	Schmidt-Cassegrain telescope (SCT)
		FIGURE 75: Schmidt-Cassegrain telescope is a Cassegrain-like two-mirror system combined with a full-aperture Schmidt corrector.
		Aberration-wise, there are two significant differences between the SCT and all-reflecting Cassegrain varieties.
		The 12" (aplanatic SCT) has much smaller off-axis blurs due to the absence of coma, while most of the increase in chromatism (~40%) is due to its larger aperture (it is roughly at the level of a 4" f/70 achromat).
	www.telescope-optics.net /SCT.htm (1906 words)

	13: Virtual Telescope II: Cassegrain
		This telescope design represents a big leap in sophistication from the Galilean telescope of the previous page, and it represents the passage of many years in the history of astronomy and telescope design.
		In a commercial Cassegrain design (called a "Schmidt-Cassegrain"), a spherical primary mirror is used instead of parabolic, because spherical mirrors are much easier to figure, and the glass plate to the right is shaped to create the optical behavior that would have been obtained with a parabolic mirror.
		Those who have telescope design experience will immediately recognize that the color distortions in the eyepiece view arise from the use of a plain eyepiece lens without any effort to correct for chromatic aberration (and as demonstrated and explained in the prior telescope page of this section).
	www.arachnoid.com /raytracing/telescope2.html (1312 words)

	Cassegrain reflector - Wikipedia, the free encyclopedia
		The Cassegrain reflector is a combination of two mirrors used in some telescopes, which are then known as Cassegrain telescopes.
		First developed in 1672 by Laurent Cassegrain, this reflector is a combination of a primary concave mirror and a secondary convex mirror, both aligned symmetrically about the optical axis.
		Another descendant of the Cassegrain design is the Ritchey-Chrétien telescope, which uses a hyperboloid primary and secondary mirror, eliminating the corrector plate needed for the catadioptic telescopes.
	en.wikipedia.org /wiki/Cassegrain_telescope (298 words)

	Reflecting telescope - Wikipedia, the free encyclopedia
		A reflecting telescope (reflector) is an optical telescope which uses a combination of curved and plane (flat) mirrors to reflect light and form an image, rather than lenses to refract or bend light to form an image.
		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 Coudé design is similar to the Cassegrain except no hole is drilled in the primary mirror; instead, a third mirror reflects the light to the side, and further optics deliver the light to a fixed focus point that does not move as the telescope is reoriented.
	en.wikipedia.org /wiki/Reflecting_telescope (2076 words)

	Telescope - Wikipedia, the free encyclopedia
		Telescopes work by employing one or more curved optical elements - lenses or mirrors - to gather light or other electromagnetic radiation and bring that light or radiation to a focus, where the image can be observed, photographed or studied.
		Newtonian or reflecting telescopes employ the reflective properties of light, using a concave paraboic primary mirror to collect and focus incoming light onto a flat secondary (diagonal) mirror that in turn reflects the image through an opening at the side of the main tube and into the eyepiece.
		The telescope was aimed by the aid of a Foucault sidérostat, which is a movable plane mirror with a 2-meter diameter, mounted in a large cast-iron frame.
	en.wikipedia.org /wiki/Telescope (2065 words)

	Cassegrain telescope
		A type of reflecting telescope with a folded optical path achieved by two mirrors – a large concave paraboloidal primary with a central hole and a small hyperboloidal convex mirror mounted on the large front corrector plate.
		In an alternate scheme, called a modified Cassegrain, a small optical flat placed immediately in front of the primary brings the light out to the side of the telescope tube and eliminates the need for a perforated primary.
		The Dall-Kirkham telescope is a variant of the Cassegrain that uses a concave ellipsoidal primary mirror and a convex spherical secondary.
	www.daviddarling.info /encyclopedia/C/Cassegrain_telescope.html (221 words)

	Cassegrain Primer - Characteristics of Cassegrains
		The two are primarily differentiated by their secondary mirrors, the Gregorian utilizes a concave mirror placed beyond the focal point of the primary mirror and the Cassegrain utilizes a convex secondary mirror placed somewhat inside of the focus of the primary mirror.
		The original postulation for the Cassegrain telescope was to have a primary parabolic mirror focusing its rays onto a convex hyperbolic secondary mirror; the classical Cassegrain.
		Applied to the Cassegrain design these relatively simple formulas began to reveal the fact that by juggling the asphericity between the two mirrors off axis aberrations could be controlled; practically speaking, essentially reduced where possible and appropriate.
	www.rfroyce.com /cassegrains.htm (1923 words)

	Buying a Telescope
		Most telescopes can be used at either high or low power by changing the eyepiece, and so good quality eyepieces are useful additions for any telescope.
		To determine the magnification of an eyepiece, divide the focal length of the telescope by the focal length of the eyepiece.
		The finder scope is the small scope on the side of a telescope and is used to aim the telescope.
	www.aw-wrdsmth.com /scuttlebutt/Buying-a-Telescope.html (1193 words)

	A Glossary for Telescope Buyers and Users
		In the strictest sense, a Cassegrain telescope is a reflecting telescope that uses two curved mirrors of particular shapes to form the image: The primary mirror is a concave paraboloid, just as in a Newtonian.
		Thus, a telescope with a clear aperture of 150 mm, having an obstruction that is 50 mm in diameter, experiences the same loss of contrast whether we report the obstruction as 0.33 (ratio of diameters) or 0.11 (ratio of areas).
		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)

	Orion StarMax 102mm Compact Maksukov Cassegrain Telescope
		This compact Maksutov Cassegrain is ideal for the more advanced home astronomer who wants a highly portable telescope that delivers sharp, high-power views of the night sky.
		A Maksutov Cassegrain telescope uses two mirrors and a front correcting lens to "fold" the light.
		The maximum theoretical magnification is 120x for a 60mm telescope and 228x for a 114mm telescope.
	www.hometrainingtools.com /catalog/earth-space-science/telescopes-accessories/p_as-t102max.html (372 words)

	Company Seven \| Orion StarMax™ 127 Maksutov-Cassegrain Telescope (Site not responding. Last check: )
		This telescope is a particularly good choice for those in suburban settings who want to glimpse changing features on the brighter astronomical objects, or for nature watching, etc. The telescope can be easily dismounted for use as a spotting telescope or as a 1,540mm ultra telephoto lens.
		The Cassegrain aspect describes the perforated primary mirror permitting the focal plane to reach the rear of the telescope.
		Telescopes such as this often put the eyepiece at position that is only about 3 or 4 feet (0.9 or 1.2 meters) from the ground.
	www.company7.com /orion/catadioptric/starmax127.html (2769 words)

	Telescope Optics
		However, it is often found employed as a small auxiliary telescope, mounted piggy-back on the main OTA, and is used for solar observations, as an off-axis guider, or as a finder telescope.
		A wide-field Cassegrain which can easily be identified by the rather large secondary mirror, typically 40% of the primary diameter.
		This variation on the Cassegrain telescope has a primary mirror that is ellipsoidal and a secondary that is spherical.
	www.astronomical.com /TelescopeOptics.htm (997 words)

	University of London Observatory: Allen Telescope (Site not responding. Last check: )
		It was acquired by the Observatory at a cost of 42000 pounds to replace the 24-inch Newtonian/Cassegrain reflector built in 1880 by Grubb of Dublin for use by W. Wilson at his observatory in Daramona, Co. Westmeath, Ireland, and donated to UCL in 1925 by Mr.
		Accurate focussing of the Allen telescope is accomplished by moving the secondary mirror a small amount using an electric motor.
		The telescope itself acts as a light collector for astronomical equipment attached at its focal point, for example a Cassegrain spectrograph and CCD camera of 600x400 pixels, used to obtain spectroscopic observations of stars, nebulae, novae, etc.
	www.ulo.ucl.ac.uk /telescopes/allen (385 words)

	Evolution of the Maksutov-Cassegrain Telescope by John F. Gills, Ph.D.
		The main differences between Cassegrain's design and that of Gregory was that Cassegrain used a convex secondary mirror and moved it inside the focal point of the main mirror.
		Later the Schmidt Corrector Plate was applied to the Cassegrain design and the Schmidt-Cassegrain Telescope was born.
		This shell also corrected for the spherical aberration and was easier to manufacture which opened the way for the telescope we have come to know as the Maksutov-Cassegrain.
	www.weasner.com /etx/guests/mak/MAKSTO.HTM (414 words)

	Schmidt Cassegrain telescope advice - scope basics
		There are a lot of different amateur telescopes available, but a real revolution occurred some years ago when two manufacturers (Celestron and Meade) integrated a microcomputer with a telescope.
		There are a lot of GoTo telescopes available, and to sort out how they differ and why their prices cover such a large range you need to understand the three primary components of a telescope.
		This design combines a primary light-gathering mirror at the rear of the scope with a glass correcting plate at the front, on the back of which is a secondary mirror that reflects light from the primary back to a hole in the center of the primary, through which you observe the image.
	sctscopes.net /SCT_Basics/sct_basics.html (1832 words)

	Telescope Optics
		You'll be able to try new types of glass, design a telescope around that corrector shell you have parked in the basement, even compare the performance of many different eyepieces on your telescope.
		There is a marvelous diagram, the “Telescope Design Tree,” which displays the genealogy of the multitude of design types in a clear, efficient manner and updates the old adage about pictures worth a kiloword.
		It describes the optical performance of most of the types of telescope bought (or built) and used by amateurs, and explains why some are suitable for visual observations, and others for photography, some for lunar and planetary work, others for faint and extended nebulae or star clusters.
	www.willbell.com /tm/tm6.htm (833 words)

	A Portable yet Rugged Cassegrain Telescope
		A serious fault found in many Cassegrain telescopes is the practice of mounting the baffle tube directly to the primary mirror.
		Naturally, for a telescope intended to be thrown in the back of a pickup truck and taken over long rough roads to a remote observing site, this method of baffle mounting would not be acceptable.
		The optics for this telescope were acquired in a horse trade and came with badly deteriorated coatings.
	home.att.net /~jsstars/8f16/8f16.html (2882 words)

	Astromart Auctions - Nishimura Cassegrain Telescope (Site not responding. Last check: )
		This telescope was purchased from a local school board twenty years ago.
		The powers that be at the time were so pleased sith the scope they wanted to purchase 10 more but the maker in Japan was not able to build them in the timeline that the government required so the contract was cancelled.
		There it was not used much and eventually someone broke in and stole the eyepieces, a spotting scope, maybe another scope, and most of the other pieces with the exception of the main telescope, one tracking scope, the mount, motors, etc which were purchased by my father twenty years ago.
	www.astromart.com /auctions/details.asp?auction_id=1579 (611 words)

	Cassegrain Equations (Site not responding. Last check: )
		Reflecting telescopes are less expensive than refractors and when properly designed they can equal the high contrast images of a refrac¬tor without the associated chromatic aberration.
		When looking through the telescope eyepiece we actually see the magnified image of the primary mirror and the focal plane is located a short distance in front of the field lens when the image is in focus.
		A primary baffle is necessary in a Cassegrain telescope to shield the focal plane, therefore your eye, from direct light from the telescope entrance and/or stray light reflected from the telescope tune walls or other components.
	www.tnni.net /~dustymars/misc/Cass_Equ.htm (5700 words)

	Schmidt-Cassegrain Telescopes at Skies Unlimited
		This is definitely a large telescope, yet the optical tube assembly tips the scales at only 60 lbs.
		The C9 1/4-SGT telescope combines the unequaled optical excellence of a Celestron 9 1/4" Schmidt-Cassegrain telescope with a stable computerized CG-5 German equatorial mount.
		This telescope gathers nearly 1/3 more light than the eight-inch model, with an optical tube assembly that tips the scales at 58 lbs.
	www.skiesunlimited.net /index.php?CategoryID=38 (652 words)

	Upgrade of 38-inch Telescope
		Butler University's first telescope was a 6-inch refractor donated to the university in the late 1880s when the campus was located in Irvington on the east side of Indianapolis.
		The main telescope in use at Holcomb Observatory is the 38-inch Cassegrain.
		Though the 38-inch Cassegrain is structurally and mechanically sound it was initially difficult for the observer to use.
	www.butler.edu /holcomb/upgrade.html (657 words)

	Telescopes : Telescope Comparison
		Manufacturer of Dobsonian telescopes ranging from 12-1/2" to 30" in aperture.Optional accessories include the ServoCAT servo drive system which may be combined...
		On-line retailer of a wide range of telescopes, microscopes, binoculars, spottingscopes and accessories for beginner, intermediate and advanced amateur...
		Telescopes excludes all liability of any kind (including negligence) in respect of any third party information or other material made available on, or which can be accessed using, this Website.
	telescopes2.com /telescopecomparison/index.php (830 words)

	Maksutov
		In the fall of 2003 several improvements were made to the scope; new coatings to increase the throughput, several minor fixes to allow for better collimation and the addition of a JMI motofocus assembly to eliminate problems with mirror shift.
		Maksutov type telescopes and cameras have long been attractive to amateurs due to the possibility of constructing a well corrected optical system incorporating entirely (or nearly) spherical surfaces.
		Maksutovs employ a weakly diverging but strongly curved and thick lens at some point in the optical path, typically ahead of the primary mirror to produce an amount of spherical aberration that is equal but opposite in sign to that of the remaining optical system.
	www.cfht.hawaii.edu /~baril/Maksutov/Maksutov.html (5568 words)

	Cassegrain concept from the Astronomy knowledge base (Site not responding. Last check: )
		has definition An optical arrangement in which light rays striking the parabolic concave primary mirror of a reflecting telescope are reflected to the hyperbolic convex secondary mirror, and re-reflected through a hole bored in the primary to a focus behind it.
		has definition Refers to a design of reflecting telescopes in which the light collected and focussed by the large concave primary mirror is refocussed by a smaller convex secondary mirror on the same axis as the primary.
		has definition Telescope devised by Cassegrain in which an auxiliary convex mirror reflects the magnified image, upside down, through a hole in the center of the main objective mirror - i.e., through the end of the telescope itself.
	www.csi.uottawa.ca:4321 /astronomy/Cassegrain.html (238 words)

	Amazon.com: The 20-cm Schmidt-Cassegrain Telescope: A Practical Observing Guide: Books: Peter L. Manly (Site not responding. Last check: )
		The Cassegrain telescope was invented in about 1672 by Sieur Guillaume Cassegrain, a sculptor and metal founder employed by the King of France.
		The S-C telescope is distinguished by having a concave paraboloidal primary with a convex hyperboloidal secondary, compared to the Gregorian telescope with it's similarly paraboloidal primary but concave secondary, which produces an upright image, unlike the S-C which is inverted like most telescopes.
		My understanding is that the Celestron telescopes actually employ elliptical rather than paraboloidal optics, but anyway, tens of thousands of these scopes have proven their worth in the hands of new and experienced amateurs around the world for decades.
	www.amazon.com /20-cm-Schmidt-Cassegrain-Telescope-Practical-Observing/dp/0521433606 (1535 words)

	Tutorial Links
		Richard is a member of the ISS-AT (Amateur Telescope) team and has been instrumental in the implementation of this project which is supported by the Astronomical League.
		To be considered a good CBA station an amateur astronomer needs, a good telescope 8 inch or larger with electronic drive, a CCD camera and software, and Software for rapid differential photometry (variable-comparison) of the many images.
		Space Science Telescope Institute The Space Science Telescope Institute (STScI) is the astronomical research center responsible for operating the Hubble Space Telescope as an international observatory.
	astronomywebguide.com /links_higher_ed.html (3614 words)

	Telescope Design - Cassegrain (Site not responding. Last check: )
		Designed and constructed in 1672 by French sculptor Sieur Cassegrain (the telescope that bears his name is correctly called a Cassegrainian, but these days most just call it a Cassegrain).
		However, the design eventually became one of the most common for large professional telescopes and led to many variations.
		Due to the folded optical path and the effective focal length extension caused by the convex secondary, the Cassegrain and all it's variants are very compact for their focal length.
	www.earlham.edu /~rodrimi/Cassegrain.htm (381 words)

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