A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Francis Upchurch
Date: 2018 Jun 10, 04:21 -0700
Really very interesting and useful.
Being a lunar fanatic (aka lunatic? ) I wonder whether you might add something on that. It required over a hundred years of astronomical measurements and improvements in the lunar theory and maths, but Maskelyne had it working reasonably well by the early 1760s, (the St Helena voyage then the 1763 Mariners Guide.). The Admiralty and Royal Society then sponsored his production of the NA to include pre-computed 3 hourly LDs.(availabe in 1767 for the first Cook voyage.)
Maybe mention the voyage of HMS Dolphin 1766-68, discovered Tahiti, and importantly established a pretty accurate longitude, purely by lunars. (courtesy the purser, non astronomer, Harrison, no relation). The "other" Harrison's achievement even more remarkable, since he had the Mariners Guide but not the 1767 NA which included 3 hourly LDs. He had to do the long grinding maths himself.
The Dolphin's dicovery and accurate longitude enabled Cook to find Tahiti in Endeavour for the transit of Venus experiments. He also only used lunars (Charles Green , astronomer), but they had the 1767 NA for the first half of the voyage, making the calculations quicker and easier.