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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: ABC longitude calcs and PQR intercept calcs LOPS not lining up
From: David C
Date: 2026 Mar 20, 17:26 -0700
From: David C
Date: 2026 Mar 20, 17:26 -0700
In my previous post I mentioned Sumner's chord method. If azimuth is being calculated then maybe that should have been he tangent method. I think I am confusing the subject so perhaps my comment should be ignored..
What is IMHO more important is that Cloudy Weather Johnson devised a method for determining lat and long by calculation rather than by plotting. That method required the C table.
I recommend Cotter's "The Complete Nautical Astronomer" for the history of the ABC tables. Many years ago in this group there was discussion about errors in Cotter's books. Putting that aside I beiieve that he gives a good introduction to the ABC tables. Plenty of well known navigation authors get a mention.
David C
