The calculation of a ship's longitude position requires two precise measurements - the position of the stars and the time difference between the location of a ship and the time at home.
At the beginning of the 17th century British ships started to establish colonies abroad but suffered heavy losses due to inaccurate navigation. It therefore became increasingly essential to plot the exact position of ships at sea.
In 1675 John Flamsteed showed that a method to determine longitude at sea (via the position of the moon) could not possibly work given the existing astronomical data. This led to the building of the ROYAL OBSERVATORY and his appointment as the first Astronomer Royal with the specific aim of perfecting navigation. He eventually plotted the position of over 3,000 stars and established the basis of determining longitude.
However, it wasn't until the discovery of the sea-going clock that it became possible for the exact position of a ship to be calculated by reference to the time back home. Some of the extraordinary proposals to establish this essential step are recounted in the Observatory.
Website:www.rog.nmm.ac.uk
Nearby attractions: National Maritime Museum, Cutty Sark
Docklands Light Railway: Cutty Sark for Maritime Greenwich