Longitude by chronometer highest point, diminish the accuracy of determining longitude by chronometer as a method of celestial navigation. Accuracies of less than error in position are difficult to achieve using the "longitude by chronometer" method. Other celestial navigation methods involving more extensive use of both the Nautical Almanac and sight reduction tables are used by navigators to achieve accuracies of one nautical mile (1.9 km) or less. This only calculates a longitude at the assumed latitude though a position line can be drawn. The observer is somewhere along the position line. Time sight is a general method for determining longitude by celestial
History of longitude A decade later, Nevil Maskelyne, who as the newly appointed Astronomer Royal was on the Board of Longitude, armed with Mayer's tables and after his own experiments at sea trying out the lunar distance method, proposed annual publication of pre-calculated lunar distance predictions in an official nautical almanac for the purpose of finding longitude at sea. Being very enthusiastic for the lunar distance method, Maskelyne and his team of computers worked feverishly through the year 1766, preparing tables for the new Nautical Almanac and Astronomical Ephemeris. Published first with data for the year 1767, it included daily tables of the