PAUL D STEWART / SCIENCE PHOTO LIBRARY PAUL D STEWART / SCIENCE PHOTO LIBRARY
Nevil Maskelyne (1732-1811), British astronomer and Astronomer Royal, with Greenwich Royal Observatory at lower right. In 1756, Maskelyne he joined the Royal Society who, in 1761, sent him to the South Atlantic island of St Helena to observe a transit of Venus. Such transits were used to find the Earth's distance from the Sun and the size of the Solar System. During the voyage he tried to accurately determine his longitude from the Moon's position. In 1764 he sailed to Barbados to test the ability of John Harrison's marine chronometer (naval clock) H4 to find longitude. Often caricatured as the 'bad guy' in the tale of Harrison's clock, he was at first a competitor for the longitude prize with his own lunar distance calculations (which initially proved impractical for working seamen). When he became Astronomer Royal he prevaricated that Harrison's H4 clock was not absolutely accurate.
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