 The Forststernwarte Jena 50cm Cassegrain telescope. The Cassegrain reflector is a combination of two mirrors used in some telescopes, which are then known as Cassegrain telescopes. It is also used in very high gain radio antennas. Image File history File linksMetadata Size of this preview: 450 × 600 pixelsFull resolution (1200 × 1600 pixel, file size: 342 KB, MIME type: image/jpeg) Beschreibung: 50-cm-Cassegrainteleskop der Forststernwarte bei Jena, einer Aussenstelle der Volkssternwarte Urania Jena Aufnahmedatum: 11. ...
Image File history File linksMetadata Size of this preview: 450 × 600 pixelsFull resolution (1200 × 1600 pixel, file size: 342 KB, MIME type: image/jpeg) Beschreibung: 50-cm-Cassegrainteleskop der Forststernwarte bei Jena, einer Aussenstelle der Volkssternwarte Urania Jena Aufnahmedatum: 11. ...
50 cm refracting telescope at Nice Observatory. ...
A Yagi-Uda beam antenna Short Wave Curtain Antenna (Moosbrunn, Austria) A building rooftop supporting numerous dish and sectored mobile telecommunications antennas (Doncaster, Victoria, Australia) An antenna or aerial is a transducer designed to transmit or receive radio waves which are a class of electromagnetic waves. ...
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. The primary mirror usually contains a hole in the centre thus permitting the light to reach an eyepiece, a camera, or a light detector. The primary mirror is of paraboloid type, while the secondary mirror is of hyperboloid type. Events England, France, Munster and Cologne invade the United Provinces, therefore this name is know as ´het rampjaar´ (the disaster year) in the Netherlands. ...
Light path in a Cassegrain reflector Laurent Cassegrain was a Catholic priest born in the region of Chartres around 1629 and died at Chaudon (Eure-et-Loir) on August 31, 1693. ...
Reflections in a spherical convex mirror. ...
Reflections in a spherical convex mirror. ...
In telecommunication, the term optical axis has the following meanings: 1. ...
A collection of different types of eyepieces. ...
Large format camera lens. ...
A parabolic reflector (also known as a parabolic dish or a parabolic mirror) is a reflective device formed in the shape of a paraboloid of revolution. ...
Hyperboloid of one sheet Hyperboloid of two sheets In mathematics, a hyperboloid is a quadric, a type of surface in three dimensions, described by the equation (hyperboloid of one sheet), or (hyperboloid of two sheets) If, and only if, a = b, it is a hyperboloid of revolution. ...
Of the three basic types of telescopes: refractors, reflectors and catadioptrics, the Cassegrain reflector falls under the category of reflecting telescopes but is also used in Catadioptric designs. A telescope (from the Greek tele = far and skopein = to look or see; teleskopos = far-seeing) is an instrument designed for the observation of remote objects. ...
The 50 cm refractor at Nice Observatory. ...
Ritchey 24 reflecting telescope A reflecting telescope (reflector) is an optical telescope which uses mirrors, rather than lenses, to reflect light. ...
Optical systems which involve both lenses and mirrors. ...
Ritchey 24 reflecting telescope A reflecting telescope (reflector) is an optical telescope which uses mirrors, rather than lenses, to reflect light. ...
Optical systems which involve both lenses and mirrors. ...
Cassegrain designs
Light path in a Cassegrain reflector telescope Image File history File links No higher resolution available. ...
Image File history File links No higher resolution available. ...
The "Classic" Cassegrain The "Classic" Cassegrain telescope has a parabolic primary mirror, and a hyperbolic secondary mirror that reflects the light back down through a hole in the primary. Folding the optics makes this a compact design. On smaller telescopes, and camera lenses, the secondary is often mounted on an optically flat, optically clear glass plate that closes the telescope tube. This support eliminates the "star-shaped" diffraction effects caused by a straight-vaned support spider. The closed tube stays clean, and the primary is protected, at the cost of some loss of light-gathering power.
It makes use of the special properties of parabolic and hyperbolic reflectors. A concave parabolic reflector will reflect all incoming light rays parallel to its axis of symmetry to a single point, the focus. A convex hyperbolic reflector has two foci and will reflect all light rays directed at one of its two foci towards its other focus. The mirrors in this type of telescope are designed and positioned so that they share one focus and so that the second focus of the hyperbolic mirror will be at the same point at which the image is to be observed, usually just outside the eyepiece. The parabolic mirror reflects parallel light rays entering the telescope to its focus, which is also the focus of the hyperbolic mirror. The hyperbolic mirror then reflects those light rays to its other focus, where the image is observed. A parabolic reflector (also known as a parabolic dish or a parabolic mirror) is a reflective device formed in the shape of a paraboloid of revolution. ...
Ritchey-Chrétien -
Main article: Ritchey-Chrétien telescope The Ritchey-Chrétien is a specialized Cassegrain reflector which has two hyperbolic mirrors (instead of a parabolic primary). It is free of coma and spherical aberration at a flat focal plane, making it well suited for wide field and photographic observations. Almost every professional reflector telescope in the world is of the Ritchey-Chrétien design. It was invented by George Willis Ritchey and Henri Chrétien in the early 1910s. The Ritchey-Chrétien telescope or RCT is a specialized Cassegrain telescope with a hyperbolic primary and secondary mirror. ...
The Ritchey-Chrétien telescope or RCT is a specialized Cassegrain telescope with a hyperbolic primary and secondary mirror. ...
In optics (especially telescopes), the coma in an optical system refers to monochromatic aberration inherent to certain optical designs or due to imperfection in the lens or other components which results in off-axis point sources such as stars appearing distorted. ...
Ritchey 24 reflecting Telescope George Willis Ritchey (December 31, 1864 – November 4, 1945) was an American optician and telescope maker and astronomer (educated as a furniture maker) born at Tuppers Plains, Ohio. ...
Henri Chrétien (February 1, 1879 – February 6, 1956) was a French astronomer and an inventor. ...
Dall-Kirkham The Dall-Kirkham cassegrain telescope's design was created by Horace Dall in 1928 and took on the name in an article published in Scientific American in 1930 following discussion between amateur astronomer Allan Kirkham and Albert G. Ingalls, the magazine editor at the time. It uses a concave elliptical primary mirror and a convex spherical secondary. While this system is easier to grind than a classic Cassegrain or Ritchey-Chretien system, it does not correct for off-axis coma and field curvature so the image degrades quickly off-axis. Because this is less noticeable at longer focal ratios, Dall-Kirkhams are seldom faster than f/15. Scientific American is a popular-science magazine, published (first weekly and later monthly) since August 28, 1845, making it the oldest continuously published magazine in the United States. ...
For other uses, see Ellipse (disambiguation). ...
For other uses, see sphere (disambiguation). ...
A 35mm lens set to f/11, as indicated by the white dot above the f-stop scale on the aperture ring In photography the f-number (focal ratio) expresses the diameter of the diaphragm aperture in terms of the effective focal length of the lens. ...
Schiefspiegler An unusual variant of the Cassegrain is the Schiefspiegler telescope ("skewed" or "oblique reflector"), which uses tilted mirrors to avoid the secondary mirror casting a shadow on the primary. However, while eliminating diffraction patterns this leads to several other aberrations that must be corrected.
Catadioptric Cassegrains
Schmidt-Cassegrain -
Main article: Schmidt-Cassegrain
 Light path in a Schmidt-Cassegrain The Schmidt-Cassegrain is a classic wide-field telescope. The first optical element is a Schmidt corrector plate. 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. Schmidt-Cassegrains are popular with amateur astronomers. Schmidt-Cassegrain The Schmidt-Cassegrain, invented by Bernhard Schmidt, is similar to the Cassegrain. ...
Image File history File links This is a lossless scalable vector image. ...
Image File history File links This is a lossless scalable vector image. ...
Schmidt-Cassegrain The Schmidt-Cassegrain, invented by Bernhard Schmidt, is similar to the Cassegrain. ...
A Schmidt corrector plate, invented by Bernhard Schmidt in 1930[1], is a lens used to correct spherical aberration in a reflecting telescope that uses a spherical primary mirror. ...
Focal plane Longitudinal sections In optics, spherical aberration is an image imperfection that occurs due to the increased refraction of light rays that occurs when rays strike a lens or mirror near its edge, in comparison with those that strike nearer the center. ...
Maksutov-Cassegrain -
 Light path in a Maksutov-Cassegrain The Maksutov-Cassegrain is a variation of the Maksutov telescope, invented by Dmitri Dmitrievich Maksutov. It starts with an optically transparent corrector lens that is a section of a hollow sphere. It has a spherical primary mirror, and a spherical secondary that in this application is usually a mirrored section of the corrector lens. A 150mm aperture Maksutov-Cassegrain telescope. ...
Download high resolution version (814x244, 17 KB) Modified from http://de. ...
Download high resolution version (814x244, 17 KB) Modified from http://de. ...
A 150mm aperture Maksutov-Cassegrain telescope. ...
Image:Dmitry Dmitriyevich Maksutov. ...
Argunov-Cassegrain telescope -
Main article: Argunov-Cassegrain telescope In the Argunov-Cassegrain telescope all optics are spherical, and the classical Cassegrain secondary mirror is replaced by three air spaced lens elements. The element farthest from the primary mirror is a Mangin mirror, in which the element acts as a second surface mirror, having a reflective coating applied to the surface facing the sky. The Argunov Cassegrain telescope is a telescope design first introduced in 1972 by P.P. Argunov. ...
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