Folded Cassegrain
The Cassegrain reflector is a combination of a primary concave mirror and a secondary convex mirror, often used in optical telescopes and Antenna (radio), radio antennas, the main characteristic being that the optical path folds back onto itself, relative to the optical system's primary mirror entrance aperture. This design puts the Focus (optics), focal point at a convenient location behind the primary mirror and the convex secondary adds a Telephoto lens, telephoto effect creating a much longer focal length in a mechanically short system. In a symmetrical Cassegrain both mirrors are aligned about the optical axis, and the primary mirror usually contains a hole in the center, thus permitting the light to reach an eyepiece, a camera, or an image sensor. Alternatively, as in many radio telescopes, the final focus may be in front of the primary. In an asymmetrical Cassegrain, the mirror(s) may be tilted to avoid obscuration of the primary or to avoid the need for a hole in the prima ...
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Cassegrain
Cassegrain may refer to * Cassegrain reflector, a design used in telescopes * Cassegrain antenna, a type of parabolic antenna * Cassegrain (crater), on the Moon * a Belgian canned vegetables producer now part of Bonduelle S.A. People : * Guillaume Cassegrain, a French sculptor * Giovanni Cassegrain, a French sculptor * Jean Cassegrain, a French businessman, founder of Longchamp in 1948 * Laurent Cassegrain Laurent Cassegrain (; – 1 September 1693) was a Catholic priest who is notable as the probable inventor of the Cassegrain reflector, a folded two-mirror reflecting telescope design. Biography Laurent Cassegrain was born in the region of Char ...