A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Ducruy Jacques
Date: 2020 Jul 30, 08:58 -0700
In the "british mariner's guide" (1763), Maskelyne give a method for compute the longitude by lunar distance, but this method is not the methode given in the Nautical almanach 1767.
Method 1763 : from the true lunar distance, Maskelyne compute the difference of celestial longitude between the moon and the sun (or a star) ; he compute the longitude of the moon, search the longitude of the moon given by Mayer's tables for the estimed time of Greenwich, and find the longitude of the ship : it seems to me that the principle is the same that the methode of Chabert (1751) and Pingré (1756).
Method 1767 : the methode is similar to the methode of Lacaille, but with more precision : we compare here a observed distance et a cumputed distance.
But it seems that, during his travel to St Helena, he had used the two methods !
Have you some ideas on this question ?