The Nautical Almanac & Its Superintendents
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1765: Nevil Maskelyne, 5th Astronomer Royal 1765 - 1811

 
Revd. Neville Maskelyne

Revd. Neville Maskelyne by John Russell

© National Maritime Museum, London

Nevil Maskelyne (1732-1811) came from a poor family, whose parents died while he was being educated at Westminster School. His interest in astronomy began when he observed the solar eclipse of 25th July 1748.

In 1748 Maskelyne entered Cambridge University where he graduated 7th wrangler in mathematics six years later. He was ordained a minister in 1755 but did not take up the priesthood. In 1756 he became a fellow of Trinity College, Cambridge and the following year was appointed as an assistant to the Astronomer Royal, James Bradley (1742-1762). He was admitted to the Royal Society in 1758.

Maskelyne's first contribution to astronomical literature was A Proposal for Discovering the Annual Parallax of Sirius published in 1760 (Phil. Trans. ii. 889).

In 1761 he was sent by the Royal Society to the island of St Helena to observe the transit of Venus, with the aim of using the observations to calculate the distance of the Earth from the Sun. Bad weather prevented any useful observations being made, however, Maskelyne used his journey to develop the technique of calculating longitude by using Lunar Distances.

Harrison's H4 Chronometer

Harrison's H4 Chronometer

©National Maritime Museum, London

In 1763 Maskelyne published his British Mariner's Guide, which includes the suggestion that in order to facilitate the finding of longitude at sea, Lunar Distances should be calculated beforehand, for each year, and published in a form accessible to navigators. That same year the Board of Longitude asked Maskelyne to accompany Harrsion's time piece (H4) to Barbados on its second trial and to test the method of Lunar Distances. Two years later, in 1765 he was appointed Astronomer Royal, and importantly, thus also appointed to the Board of Longitude.

Maskelyne was portrayed negatively in Dava Sobel's book Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time. In fact Maskelyne did not receive a reward, but Tobias Mayer's widow was awarded £3,000 for his Lunar Tables and the Swiss mathematician, astronomer, Leonhard Euler (1707-1783) £300 on whose method the lunar tables were based [20]. While using Harrison's time piece H4 was indeed more accurate, on the other hand, Lunar Distances with Maskelyne's Nautical Almanac (NA & AE) was far cheaper. This being partly due to cost, and thus was the predominate method used for the next century. In fact the Almanac for 1906 was the last to tabulate Lunar Distances.

 

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