A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2020 May 8, 05:48 -0700
The attached pages are from Bowditch and should help explain. The formula is the one used in the Nautical Almanac and looks to be a practical approximation. To do better it is necessary to have pressure and temperature corrections as seen in table A4 of Nautical Almanac. Results will still be less than perfect even when all corrections are made but good enough for general celestial navigation.