Icon class icon_class fas fa-quote-left icon_class_computed fas fa-quote-left Related content The Gregorian telescope employs a concave secondary mirror that reflects the image back through a hole in the primary mirror. Source Wikipedia Copyright information Text from Wikipedia and Wiktionary web pages quoted for educational purposes is subject to the Wikipedia Creative Commons Attribution ShareAlike Licence Snippet kind INFO Keywords Gregorian reflector reflecting telescope reflector optical telescope telescope mirror secondary mirror primary mirror Previous snippet Full quote The Gregorian telescope ... employs a concave secondary mirror that reflects the image back through a hole in the primary mirror. This produces an upright image URL https://en.wikipedia.org/wiki/Reflecting_telescope#Technical_considerations Next snippet Related snippets A curved primary mirror is the reflector telescope's basic optical element that creates an image at the focal plane [OF THE PRIMARY IF THERE IS NO SECONDARY]. The distance from the mirror to the focal plane is called the focal length. Related snippets (backlinks) There are several large modern telescopes that use a Gregorian configuration such as the Vatican Advanced Technology Telescope, the Magellan telescopes, the Large Binocular Telescope, and the Giant Magellan Telescope. The Newtonian telescope ... usually has a paraboloid primary mirror but at focal ratios of f/8 or longer a spherical primary mirror can be sufficient for high visual resolution. A flat secondary mirror reflects the light to a focal plane at the side of the top of the telescope tube. The cassegrain telescope (sometimes called the "Classic Cassegrain") ... has a parabolic primary mirror, and a hyperbolic secondary mirror that reflects the light back down through a hole in the primary. The Ritchey–Chrétien telescope ... 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 nearly flat focal plane if the primary and secondary curvature are properly figured. A segmented mirror is an array of smaller mirrors designed to act as segments of a single large curved mirror. ... They are used as objectives for large reflecting telescopes. The Gregorian telescope consists of two concave mirrors; the primary mirror (a concave paraboloid) collects the light and brings it to a focus before the secondary mirror (a concave ellipsoid) where it is reflected back through a hole in the centre ... Diagram of the lightpath through a Gregorian telescope. Light path in a Newtonian telescope. Light path in a Cassegrain telescope. In the Gregorian design, the primary mirror creates a real image before the secondary mirror. This allows for a field stop to be placed at this location, so that the light from outside the field of view does not reach the secondary mirror. This is a major advantage for solar telescopes, where a field stop (Gregorian stop) can reduce the amount of heat reaching the secondary mirror and subsequent optical components. Visit also Visit also (backlinks) Flags
