Bras sextant supported by ropes, c 1650. P
© Science Museum / Science & Society Picture Library
Bras sextant supported by ropes, c 1650. Plate from Johannes Hevelius's (1611-1687) 'Machina Coelestis' (1673), showing Havelius's bras sextant. Hevelius was an early German astronomer, who established the foremost observatory in Danzig in 1641, rebuilding it after a fire in 1679. He catalogued 1500 stars, discovered four comets and was one of the first to observe the transit of Mercury.