Royal Observatory, Greenwich

Royal Observatory, Greenwich. Notice the time ball atop the Octagon Room.

The Royal Observatory, Greenwich (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, for John Flamsteed, to beas the director of the observatory.

He was 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".

The Observatory is on a hill in Greenwich Park in Greenwich, London, overlooking the River Thames.

The Greenwich Meridian runs through the site of the Observatory. It is the line at which the longitude is defined as 0°.

Royal Observatory, Greenwich Media

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  Greenwich Observatory (Latinized as Observatorium Anglicanum Hoc Grenovici prope Londinum), as illustrated in Johann Gabriel Doppelmayr's map of the southern celestial hemisphere, c. 1730

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  The Airy Transit Circle, used for over a century (1851–1953) as the reference point when charting the heavens and determining times, thus earning for it the epithet "the centre of time and space"

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  The building housing the origin of the Greenwich Prime Meridian, marked by the brass strip in the foreground. The apex of the roof opens up to the left above the white vertical strips (joints in the eaves are visible), enabling telescopic star sightings to be made.

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  The Shepherd Gate Clock at the gates of the Royal Greenwich Observatory. This clock shows Greenwich Mean Time all year round, ie. it is not set to British Summer Time in the summer.

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  The time ball is the red ball on a post – when it drops a certain time is signalled. This allowed clocks to be set from afar with great accuracy, particularly the chronometers of ships on the River Thames below, prior to sailing. The observatory would first determine the time by stellar observations.

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  Former Royal Greenwich Observatory, Herstmonceux, East Sussex

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  Greenwich House at Cambridge

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  The Magnetic Pavilion, 1900

Other websites

• HM Nautical Almanac Office Archived 2007-06-30 at the Wayback Machine
• The Royal Observatory, Greenwich Archived 1999-04-20 at the Wayback Machine
• Aerial View of The Royal Observatory, Greenwich at Google Maps
• The National Maritime Museum Archived 2011-12-12 at the Wayback Machine
• The RGO at Herstmonceux Archived 2008-12-05 at the Wayback Machine
• The Observatory Science Centre
• Isaac Newton Group of Telescopes Archived 2015-07-29 at the Wayback Machine