D7061

Transit instrument Long Caption: In July 1816 Edward Troughton's ten foot (3 m) transit instrument telescope replaced Bradley's earlier instrument, and reconfirmed Bradley's meridian as the prime meridian for the Royal Observatory, Greenwich, until December 1850. The telescope itself was regularly calibrated by taking sightings off a number of distant markers. In 1824 a granite obelisk was erected at Chingford, Essex, some eleven miles (18 km) to the north. The Bradley Obelisk, as it is known, still stands. The telescope was commissioned by the Astronomer Royal John Pond after the mural circle (AST0973), installed a few years earlier had been found insufficiently stable for taking accurate transit observations. On the centre of the telescope's axis the maker has inscribed: 'Designed and Executed for the Royal Observatory by Edward Troughton, London, 1816' on one side and on the other 'To the President of the Council of the Royal Society this and the Mural Circle, being his greatest and best works, are dedicated by the maker'. The telescope now sits (and has done since 1967) on replica piers in the same site in which it sat in 1816. Credit line: © National Maritime Museum, Greenwich, London Object: AST0982 Artist: Troughton Dollond Date: 1816 Size: Overall: 3048 mm x 127 mm Click here to buy a bespoke print of this image.