NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lunars for dummies like me
From: Jan Kalivoda
Date: 2004 Sep 24, 15:51 +0200
From: Jan Kalivoda
Date: 2004 Sep 24, 15:51 +0200
Jim Thompson wrote: >Was it is as obvious as it seems to be -- simply adding the >number of hours and minutes of LAT to 1200, >and then adjusting the hands of >the clock to match that time? If I understand you well, Jim, I agree with you. The time sight of the Sun gave sailors a reliable westing or easting LHA of the "apparent" = true Sun, the dial pointer of LAT. If you express it in hours, minutes and seconds, then the task of obtaining LAT is simple arithmetics, adding westing LHA or subtracting easting LHA to/from 12 and setting the clock accordingly. Of course, old seamen used to gain LHA in time units directly, as their logarithmic result (by most formulas using measured altitude of the Sun, DR latitude and declination of the Sun) was log hav LHA, tabulated as "log rising" against arguments in time units. In addition, in many tables they could immediately read the time from the precedent midnight (= LAT during AM hours) for easting LHA's of the Sun. The date of their observation was another issue. The civil, astronomical (almanac) or nautical date - they had to choose. George Huxtable wrote the article on this problem for the list some time ago. Jan Kalivoda