NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Robin Stuart
Date: 2015 Sep 30, 09:07 -0700
Gary is of course right about this. Berson's procedure introduces an unnecessary sexagesimal subtraction of the longitude. In practice you'll still need to add your longitude (converted to time) to the GMT of Nautical Twilight to order to convert to local time but not to set up the Rude Star Finder. To put some numbers on it (and keeping all digits) Gary's procedure for 10 October, 2015 gives
Greenwich Nautical Twilight End: 5h 07m
GHA of Aries at 5h: 93°29.2'
GHA increment of Aries for 7m: 1°45.3'
This gives a result 95°14.5' as compared with Berson's 95° and is entirely adequate for the job in hand. It requires consulting just 2 pages in the NA.
Other issues with Berson's solutions to CelNav problems in ON have been discussed here previously under the heading Berson's Noon Sun problem
Robin Stuart
