The Royal Observatory, Greenwich (formerly the Royal Greenwich Observatory or RGO) was commissioned in 1675 by King Charles II. At this time the king also created the position of Astronomer Royal (initially filled by John Flamsteed), 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." It is situated on a hill in Greenwich Park in Greenwich, London, overlooking the River Thames.

Today the buildings include a museum of astronomical and navigational tools, notably including John Harrison's prize-winning longitude chronometer, H4 and its three predecessors. It is also home to the 28-inch Grubb refracting telescope the largest of its kind in the UK. The Shepherd Clock outside the observatory gate is an early example of an electric slave clock. In February 2005 construction work began on a £15 million redevelopment project which will provide a new planetarium and additional display galleries and educational facilities.

Royal Observatory Greenwich website