who made observations to investigate the reliability of the lunar distance
method for determining longitude at sea. In 1774 he estimated the mass
of the Earth by noting the deflection of a plumb line near Mount Schiehallion
Maskelyne, the fifth Astronomer Royal 1765-1811, began publication 1766
of the Nautical Almanac. This contained astronomical tables and navigational
aids, and was probably his most enduring contribution to astronomy.
Maskelyne was born in London and studied at Cambridge. He was ordained
a cleric but began working at the Greenwich Observatory in London. His
first big project in observational astronomy was an expedition to St
Helena, under the auspices of the Royal Society, in order to study the
solar parallax during the 1761 transit of Venus. At the appropriate
moment, however, the weather turned bad and, in any case, he had lost
confidence in the instruments he had brought with him. It was not until
1772 that Maskelyne perfected his technique for observing transits,
by which time the 1769 transit of Venus had already occurred (and the
next would not take place in his lifetime).