Repro ID: D6849_1 Title: The Royal Observatory, Greenwich. Description: The Observatory, showing the time-ball. Erected in 1833, the Greenwich time-ball was one of the world's first visual time signals. The ball, which drops daily at 1300, was used to check marine chronometers by sailors on the Thames. The Royal Observatory, under the 5th Astronomer Royal, Nevil Maskelyne, was closely involved in the planning of Cook's voyages as it was the heart of astronomical research in Britain. Astronomers travelled on all Cook's voyages to help in navigation and charting. Creator: Unknown Date: unknown Credit line: National Maritime Museum, London
