Astrograph


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astrograph

[′as·trō‚graf]
(astronomy)
A telescope designed to be used exclusively for astronomical photography.
(mapping)
A device for projecting a set of precomputed altitude curves onto a chart or plotting sheet, the curves moving with time such that if they are properly adjusted, they will remain in the correct position on the chart or plotting sheet; used in mapping the heavens.

Astrograph

 

an astronomical instrument for photographing celestial objects. Astrographs are constructed according to the designs of refractors, reflectors, or mirror-lens telescopes (Schmidt telescope, Maksutov telescope, and others). A filmholder with a photographic plate is fitted on the eyepiece end of the astrograph. The rotation of the astrograph in synchronism with the daily motion of the celestial sphere is achieved by an accurate timing mechanism and is controlled by the observer with the aid of a guide—a second optical tube which is fixed parallel on the same mounting. Some astrographs just use a photoelectric guide to automatically hold the star at a fixed point on the photographic plate.

The astrograph’s main feature is the focal length of the lens or the main mirror and the aperture size of the instrument. Short-focus, wide-angle astrographs are used to photograph stars over large areas of the sky, meteors, artificial earth satellites, comets, and asteroids. These astrographs have focal lengths of less than 1 and cover several tens or more square degrees of the sky. For more accurate measurements of the positions of stars and planets as well as of the proper motion of stars, astrographs with focal lengths of several meters are used. These are the so-called normal astrographs (focal length 3.5 m) and zonal astrographs (2.0 m). Astrographs with the longest focal lengths (7–19 m) are used for the highly accurate work of determining star parallaxes and measuring binary stars. The main advantage of mirror astrographs is their high aperture, which allows relatively short exposure times for photographing very faint objects, specifically of space probes receding from the earth.

A. N. DEICH

References in periodicals archive ?
Another Sobral telescope, known as an astrograph, also produced lots of star images, but they were blurred and out of focus, perhaps because heat from the sun had affected the telescope mirror.
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The Pohl Observatory has a 24-inch Corrected Dall-Kirkham Astrograph telescope that was made possible by a donation from Emeritus Chemistry faculty--Dr.
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Q: I read that a new survey camera was incorporated into the astrograph telescope.
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8 astrograph and wide-band clear filter at a remotely-operated observatory near Mayhill, New Mexico, USA.
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And for many this new 70-mm f/5 astrograph incorporating ED-glass lenses in a 4-element Petzval design is an ideal instrument.
Using frames taken on 2010 May 25 & 30 at the remotely operable Sierra Stars Observatory, California, we measured the position of target star TW CrB with Astrometrica using the UCAC3 (US Naval Observatory Astrograph CCD, 2009) catalogue.