A Schmidt camera is an astronomical camera designed to provide wide fields of view with limited aberrations. Other similar designs are the Wright Camera and Lurie-Houghton telescope. Astronomy (Greek: αστρονομία = άστρον + νόμος, literally, law of the stars) is the science involving the observation and explanation of events occurring beyond the Earth and its atmosphere. ... A camera is a device used to take pictures (usually photographs), either singly or in sequence, with or without sound, such as with video cameras. ... Your field of view is that part of the observable world that you are able to see at any given moment. ... Aberration in optical systems (lenses, prisms, mirrors or series of them intended to produce a sharp image) generally leads to blurring of the image. ...

Invention and Design

The Schmidt camera was designed by Bernhard Schmidt (1879-1935). Its optical components are an easy to make spherical primary mirror, and an aspherical correcting lens, known as a corrector plate, located at the radius of curvature of the primary mirror. The film or other detector is placed inside the camera, at the prime focus. The design is noted for allowing very fast focal ratios, while controlling coma and astigmatism. Bernhard Schmidt (1879–1935) was an Estonian-born optician who lived in German. ... A sphere is, roughly speaking, a ball-shaped object. ... A primary mirror is a form of distributed data management on the Internet. ... A lens is a device for either concentrating or diverging light, usually formed from a piece of shaped glass. ... A Schmidt corrector plate, invented by Bernhard Schmidt in 1931, is a lens used to correct spherical aberration in a reflecting telescope that uses a spherical primary mirror. ... 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. ... 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. ... Aspherical cornea (top, exagerated) and normal eye below. ...

Schmidt cameras have very strongly curved focal planes, thus requiring that the film, plate, or other detector be correspondingly curved. In some cases the detector is made curved; in others flat media is mechanically conformed to the shape of the focal plane through the use of retaining clips or bolts, or by the application of a vacuum. The focal plane of a lens is a plane that is perpendicular to the axis of the lens and passes through its focus. ... The article on the vacuum cleaner is located elsewhere. ...

Applications

The Schmidt camera is typically used as a survey instrument, for research programs in which a large amount of sky must be covered. These include astronomical surveys, comet and asteroid searches, and nova patrols. Comet Hale-Bopp, showing a white dust tail and blue gas tail (February 1997) A comet is a small astronomical object similar to an asteroid but composed largely of ice. ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... A nova is a cataclysmic nuclear explosion caused by the accretion of hydrogen onto the surface of a white dwarf star. ...

In addition, Schmidt cameras and derivative designs are frequently used for tracking artificial earth satellites.

Starting in the early 1970s, Celestron marketed an 8-inch Schmidt Camera. The camera was focused in the factory and was made of materials with low expansion coefficients so it would never need to be focused in the field. Early models required the photographer to cut and develope individual frames of 35mm film as the film holder could only hold one frame of film. About 300 Celestron Schmidt Cameras were produced. Events and trends Although in the United States and in many other Western societies the 1970s are often seen as a period of transition between the turbulent 1960s and the more conservative 1980s and 1990s, many of the trends that are associated widely with the Sixties, from the Sexual Revolution...

The Schmidt system was popular, used in reverse, for television projection systems. Large Schmidt projectors were used used in theaters but systems as small as 8-inches were made for home use and other small venues.

Arguably the most famous and productive Schmidt camera is the Oschin Schmidt Telescope at Palomar Observatory. It was used for the National Geographic Society - Palomar Observatory Sky Survey (POSS), the POSS-II survey, the Palomar-Leiden (asteroid) Surveys, and other projects. The telescope used in the Lowell Observatory Near-Earth-Object Search (LONEOS) is also a Schmidt camera. Palomar Observatory is a privately-owned observatory located in San Diego County, California, 90 miles (145 km) southeast of Mount Wilson Observatory, on Palomar Mountain. ... The National Geographic Society - Palomar Observatory Sky Survey (NGS-POSS) is a major photographic survey of the night sky completed at Palomar Observatory in 1958. ... Lowell Observatory Near-Earth-Object Search (LONEOS) is a program run by NASA and Lowell Observatory to discover near-Earth objects. ...

Derivative Designs

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. This removes spherical aberration while preserving the wide field of the short focal-length mirror. However, it is at the cost of light-gathering ability. Although this solution was well-known long before Bernhard Schmidt invented his corrector plate the design is known as a "lensless Schmidt".

In 1940, James Baker of Harvard University modified the Schmidt camera design to include a convex secondary mirror, which reflected light back toward the primary. The photographic plate was then installed near the primary, facing the sky. This variant is called the Baker-Schmidt camera. Harvard University is a private university in Cambridge, Massachusetts, USA and a member of the Ivy League. ...

The Baker-Nunn design replaces the Baker-Schmidt camera's corrector plate with a small triplet corrector lens closer to the focus of the camera.

The Mersenne-Schmidt camera consists of a concave paraboloidal primary mirror, a convex spherical secondary mirror, and a concave spherical tertiary mirror.

The addition of a flat secondary mirror at 45° to the optical axis of a Schmidt camera creates a Schmidt-Newtonian telescope. This design is popular amongst amateur astronomers. A secondary mirror (or secondary) is a second light gathering and focusing surface in a reflector telescope. ... Amateur astronomy, often called back yard astronomy, is a hobby whose participants enjoy observing celestial objects. ...

The addition of a convex secondary mirror directing light through a hole in the primary mirror creates a Schmidt-Cassegrain Telescope.