Information AboutAstrograph |
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Wide-angle astrographs with focal distance less than 1 m are used for photographing a huge sky areas with an images of Meteor s, Comet s and artificial satellites. Astrographs with focal distance under 10-15 m are used in precise measurements. Many observatories of the world are equipped with the so-called normal astrographs with focal length 3-4 m. In 2004 , Celestron announced they were producing an astrograph of 20 inch aperture (51 cm) based on a corrected Dall-Kirkham design. Although priced at $40,000 USD , this brings this class of instrument within reach of the very affluent end of the Amateur Astronomy market. . Optical system Sonnefeld 4-lens Apochromat since 1968 , Aperture 30.0 cm, Focal Length 150 cm, image scale 138"/mm (13 mm = 30')]] was used in the discovery of Pluto .]] |