Basic Guidelines For English Spellings
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1Astronomy
A device for determining the positions of stars; especially a telescope used for photographing the night sky, specifically one using wide-angle photographs to detect celestial objects or to determine their position.
2Aeronautics Nautical
historical A navigational device that projects a set of curves of equal altitude for a given star on to a navigational chart or plotting sheet.
Mid 19th century; earliest use found in The Literary Gazette. From astro- + -graph.