F8640-001

Telescope, quadrant Long Caption: This quadrant was given to William Herschel by fellow-astronomer Alexander Aubert in 1786. The quadrant was fixed to the large twenty foot telescope by William on 24 June 1789 and was later used with his forty foot telescope. Like other astronomical quadrants, this instrument is made up of a minimum of two radial bars joined together at one end at right angles to each other, and a scale, covering a quarter of a circle's circumference, joining the two bars at their other ends. The scale is marked out in degrees from 0 to 90. Pivoted at the point at which the two bars meet (at the centre of the circle) is a moveable sighting bar. Credit line: © National Maritime Museum, Greenwich, London. Object: AST0976 Artist: John Bird Date: circa 1760 Medium: brass Size: radius: 330.2 mm Click here to buy a bespoke print of this image.