In 1763 the Board of Longitude sent Maskelyne to Barbados in order to carry out an official trial of three contenders for a Longitude reward. He was to carry out observations on board ship and to calculate the longitude of the capital, Bridgetown by observation of Jupiter's satellites. The three methods on trial were John Harrison's sea watch (now known as H4), Tobias Mayer's lunar tables and a marine chair made by Christopher Irwin, intended to help observations of Jupiter's satellites on board ship. Both Harrison's watch and lunar-distance observations based on Mayer's lunar tables produced results within the terms of the Longitude Act, although the former appeared to be more accurate. Harrison's watch had produced Bridgetown's longitude with an error of less than ten miles, while the lunar-distance observations were accurate to within 30 nautical miles.
In 1763 the Board of Longitude sent Maskelyne to Barbados in order to carry out an official trial of three contenders for a Longitude reward He was to carry out observations on board ship and to calculate the longitude of the capital, Bridgetow,n by observation of Jupiter's satellites The three methods on trial were John Harrison's sea watch (now known as H4), Tobias Mayer's lunar tab.les and a marine .chair made by Christopher Irwin, intended to help observations of Jupiter's satellites on board ship. Both Harrison's watch and lunar-distance observations based on Mayer's lunar tables produced results within the terms of the Longitude Act although the former appeared to be more accurate. Harrison's watch had produced Bridgetown's longitude with an error of less than ten miles, while the lunar-distance observations were accurate to within 30 nautical miles.