Royal Observatory, Greenwich

The Royal Observatory, Greenwich (ROG;[1] known as the Old Royal Observatory from 1957 to 1998, when the working Royal Greenwich Observatory, RGO, temporarily moved south from Greenwich to Herstmonceux) is an observatory situated on a hill in Greenwich Park in south east London, overlooking the River Thames to the north. It played a major role in the history of astronomy and navigation, and because the Prime Meridian passes through it, it gave its name to Greenwich Mean Time, the precursor to today's Coordinated Universal Time (UTC). The ROG has the IAU observatory code of 000, the first in the list.[2] ROG, the National Maritime Museum, the Queen's House and the clipper ship Cutty Sark are collectively designated Royal Museums Greenwich.[1]

Royal Observatory
Royal Observatory, Greenwich. A time ball sits atop the Octagon Room.
Alternative namesRoyal Greenwich Observatory
Observatory code 000 
LocationGreenwich, Royal Borough of Greenwich, Greater London, London, England
Coordinates51°28′40″N 0°00′05″W
TelescopesAltazimuth Pavilion At The Royal Observatory 
Location of Royal Observatory, Greenwich
Related media on Wikimedia Commons
Flamsteed House in 1824
Royal Observatory, Greenwich c. 1902 as depicted on a postcard

The observatory was commissioned in 1675 by King Charles II, with the foundation stone being laid on 10 August. The site was chosen by Sir Christopher Wren, a former Savilian Professor of Astronomy; as Greenwich Park was a royal estate, no new land needed to be bought.[3] At that time the king also created the position of Astronomer Royal, to serve as the director of the observatory and to "apply himself with the most exact care and diligence to the rectifying of the tables of the motions of the heavens, and the places of the fixed stars, so as to find out the so much desired longitude of places for the perfecting of the art of navigation." He appointed John Flamsteed as the first Astronomer Royal. The building was completed in the summer of 1676.[4] The building was often called "Flamsteed House", in reference to its first occupant.

The scientific work of the observatory was relocated elsewhere in stages in the first half of the 20th century, and the Greenwich site is now maintained almost exclusively as a museum, although the AMAT telescope became operational for astronomical research in 2018.