A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Francis Upchurch
Date: 2018 Jul 24, 02:39 -0700
I agree with Greg,
I think we are talking about using lunar altitudes to estimate time/longitude? (not lunar distances)
Letcher describes his method Ch 17 page 96.
Chichester describes a simplified graphical method in Along the Clipper way page 170. This method is explained with worked example in Hewith Schlereth (yes, our very own!) Commonsense Celestial Navigation page 134.
I've tried the Chichester graphical method a couple of times, not very accurate (about 30-40 miles out) but probably better then nothing.
Bye the way, Chichester was a bit naughty I think, implying his idea was original.
He had Raper's Navigation circa 1840 on board to find out how to do lunars. He didn't like the maths so came up with his simpler altitude method..
What he doesn't mention is that there is a whole chapter devoted to longitude by lunar altitudes in Raper! Albeit not his graphical method, but surely he must have seen that to stimulate the idea? Nothing new under the sun (or moon!)