The Nautical Almanac

[2][3][4] A detailed account of how the publication was produced in its earliest years has been published by the National Maritime Museum.

(For many years, official nautical almanacs and astronomical ephemerides in the UK and the USA had a linked history, and they became merged in both titles and contents in 1981.

)[4] In the UK, the official publications have been:[3][7] The main distinctive feature of the inaugural issue for 1767 was the tabulation of lunar distances as a tool to facilitate the determination of longitude at sea from observations of the Moon.

[8] Within a few years, the publishers of almanacs of other countries began to adopt the practice of tabulating lunar distances.

This was on the grounds that an important class of user was the 'Mariner', and that 'apparent Time' was "the same which he will obtain by the Altitudes of the Sun or Stars in the Manner hereafter prescribed".