Royal Greenwich Observatory

The original site of the Royal Greenwich Observatory (RGO), which was built as a workplace for the Astronomer Royal, was on a hill in Greenwich Park in Greenwich, London, overlooking the River Thames. The Prime Meridian, to which longitude refers, went through the observatory. It is marked by a brass strip in the courtyard and, since December 16, 1999, a powerful green laser shining north across the London night sky.

Further reading

• Greenwich Observatory: ... the Royal Observatory at Greenwich and Herstmonceux, 1675-1975. London: Taylor & Francis, 1975 3v. (Vol. 1. Origins and early history (1675-1835), by Eric G. Forbes. ISBN 0-8506-6093-9; Vol. 2. Recent history (1836-1975), by A.J. Meadows. ISBN 0-8506-6094-7; Vol. 3. The buildings and instruments by Derek Howse. ISBN 0-8506-6095-5)