Nevil Maskelyne. Portrait of the English astronomer Nevil Maskelyne (1732-1811), an Astronomer Royal. In 1756 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 distance of the Earth from the Sun and the size of the Solar System. During the voyage he attempted to accurately determine the ship's longitude from the Moon's position. In 1764 he sailed to Barbados to test Harrison's naval timepiece H4. On his return in 1765, Maskelyne became Astronomer Royal. He later carried out an experiment to determine the Earth's density. Artwork from an 1833/37 book.