 A 13-inch, f/5.3 astrograph at Lowell Observatory (a refractor with a 3 element lens) that was used in the discovery of Pluto. An Astrograph (astrographic camera) is a telescope designed for the sole purpose of astrophotography. Astrographs are usually used in wide field surveys of the night sky as well as detection of objects such as asteroids, meteors, and comets. Image File history File links Download high resolution version (1995x2976, 619 KB)Astrograph at Lowell Observatory used in the discovery of Pluto. ...
Image File history File links Download high resolution version (1995x2976, 619 KB)Astrograph at Lowell Observatory used in the discovery of Pluto. ...
Lowell Observatory Percival observing Mars from the Clark telescope at the Lowell Observatory. ...
Adjectives: Plutonian Atmosphere Surface pressure: 0. ...
Astrophotography is a specialised type of photography that entails making photographs of astronomical objects in the night sky such as planets, stars, and deep sky objects such as star clusters and galaxies. ...
Asteroids is a popular vector-based video arcade game released in 1979 by Atari. ...
Photo of a burst of meteors with extended exposure time A meteor is the visible path of a meteoroid that enters the Earths (or another bodys) atmosphere, commonly called a shooting star or falling star. ...
Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ...
Design
Most research telescopes in this class are refractors although there are many (usually larger) reflecting designs such as the Ritchey-Chrétien and Catadioptrics such as the Schmidt camera. The main parameters of an Astrograph are the diameter and f-ratio of the objective which determine the field of view and image scale on the photographic plate or CCD detector. The objective of an Astrograph is usually not very large, on the order of 8-20 inches (20 - 50 cm). Image of a refracting telescope from the Cincinnati Observatory in 1848 A refracting or refractor telescope is a dioptric telescope that uses a lens as its objective to form an image. ...
A reflecting telescope (reflector) is an optical telescope which uses a combination of curved and plane (flat) mirrors to reflect light and form an image (catoptric), rather than lenses to refract or bend light to form an image (dioptric). ...
The Ritchey-Chrétien telescope or RCT is a specialized Cassegrain telescope designed to eliminate coma, thus providing a relatively large field of view as compared to a more conventional configuration. ...
Optical systems which involve both lenses and mirrors. ...
Optical ray paths inside Schmidt camera 2m Schmidt Camera (Alfred-Jensch-Telescope Tautenburg, Thuringia, Germany A Schmidt camera is an astronomical camera designed to provide wide fields of view with limited aberrations. ...
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. ...
Several objective lenses on a microscope. ...
The field of view is the part of the observable world that is seen at any given moment. ...
CCD can stand for: Cafe Coffee Day, a chain of coffee shops in India Charge-coupled device, an electronic light sensor used in digital cameras Colony Collapse Disorder, a mysterious die-off of commercial honeybees Confraternity of Christian Doctrine, a Catholic association devoted to teaching religion Carbonate Compensation Depth, a...
The shape of the focal plane is often designed to work in conjunction with a specific shaped photographic plate or CCD detector. The objective is designed to produce a particularly large (sometimes as larger as 17x17 inches), flat, and distortion-less image at the focal plane. They may even be designed to focus certain wavelengths of light to match the type of film they are designed to use (early Astrographs were corrected to work in blue wavelengths to match photographic emulsions of the time). The focal plane of a lens is a plane that is perpendicular to the axis of the lens and passes through its focus. ...
Wide-angle astrographs with short f-ratios are used for photographing a huge area of sky. Astrographs with higher f-ratios are used in more precise measurements. Many observatories of the world are equipped with the so-called normal astrographs with an aperture of around 13 inches (330 mm) and a focal length of 11 feet (3.4 m). The purpose of a “normal astrograph” is to create images where the scale of the image at the focal plane is a standard of approximately 60 arcsecs/mm A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60) of one degree. ...
Applications
A Double Astrograph consisting of 2 six inch astrographs and a central guide scope on display at Heidelberg-Königstuhl observatory in Germany Image File history File linksMetadata No higher resolution available. ...
Image File history File linksMetadata No higher resolution available. ...
Astrometry Astrographs used in Astrometry record images that are then used to “map” the positions of objects over a large area of the sky. These maps are then published in catalogs to be used in further study or to serve as reference points for deep-space imaging. Illustration of the use of optical wavelength interferometry to determine precise positions of stars. ...
Stellar classification Astrographs used for stellar classification sometimes consist of two identical telescopes on the same mount (a Double Astrograph). Each sky field can be simultaneously photographed in two colors (usually blue and yellow). Both telescopes are individually designed to focus the desired wavelength of light that is combined with the respective color sensitive (black-and-white) photographic plate. In other cases a single telescope is used to make two exposures of the same part of the sky with different filters and color sensitive film used on each exposure. Two-color photography lets astronomers measure the color, as well as the brightness (magnitude), of each star imaged. Colors tell the star's "temperature”. Knowing the color type and magnitudes lets astronomers determine the star’s distances. Sky fields that are photographed twice, decades apart in time, will reveal a nearby stars' proper motion when measured against the background of distant stars or galaxies. In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ...
The proper motion of a star is the motion of the position of the star in the sky (the change in direction in which we see it, as opposed to the radial velocity) after eliminating the improper motions of the stars, which affect their measured coordinates but are not real...
Discovery of astronomical objects
 The photographic plates that were used to discover Pluto. By taking two exposures of the same section of the sky days or weeks apart it is possible to find objects such as asteroids, meteors, comets, variable stars, nova, and even unknown planets. By comparing the pair of images astronomers are able to find a 'star' that moved between the two exposures or simply appears in one image only in the case of a nova. Sometimes objects can even be found in one exposure since a fast moving object will appear as a “line” in a long exposure. Image File history File links Download high-resolution version (1779x1101, 674 KB) This image is a faithful digitalization of a unique historic photograph, and the copyright for it is most likely held by the photographer who took the photograph or the agency employing the photographer. ...
Image File history File links Download high-resolution version (1779x1101, 674 KB) This image is a faithful digitalization of a unique historic photograph, and the copyright for it is most likely held by the photographer who took the photograph or the agency employing the photographer. ...
Adjectives: Plutonian Atmosphere Surface pressure: 0. ...
Asteroids is a popular vector-based video arcade game released in 1979 by Atari. ...
Photo of a burst of meteors with extended exposure time A meteor is the visible path of a meteoroid that enters the Earths (or another bodys) atmosphere, commonly called a shooting star or falling star. ...
Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ...
This article or section contains a plot summary that is overly long or excessively detailed. ...
Artists conception of a white dwarf star accreting hydrogen from a larger companion A nova (pl. ...
The eight planets and three dwarf planets of the Solar System. ...
One well know case of an astrograph used in a discovery is Clyde Tombaugh’s discovery of the dwarf planet Pluto in 1930. Tombaugh was given the job of hunting for a suspected “9th planet” which was achieved by systematically photographing the area of the sky around the ecliptic. Tombaugh used Lowell Observatory's 13-inch (3 lens element), f/5.3 refractor astrograph which recorded images on 14x17 inch glass plates. An image of Clyde Tombaugh Clyde William Tombaugh (February 4, 1906 – January 17, 1997) was an American astronomer who discovered the dwarf planet Pluto in 1930. ...
Artists impression of Pluto (background) and Charon (foreground). ...
Adjectives: Plutonian Atmosphere Surface pressure: 0. ...
The plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ...
Lowell Observatory Percival observing Mars from the Clark telescope at the Lowell Observatory. ...
Sources
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