A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Tony Oz
Date: 2017 Oct 22, 08:29 -0700
Yesterday, 2017-10-21 it was a clear sunset over the Finnish Gulf so I could take the timind. According to my wristwatch with +3sec error the upper limb has crossed the horizon at 14:33:15UT. At the time I was standing on the shore at N60d06m45s;E029d56m42s.
Checking that position and time on the USNOA site gave me the Sun Hc equal to -47m.
The weather was cold, and a distant fort normally having approx. 4 arcmin height was just barely popping up on the horizon. This,I think, explains why it was -47m rather than expected -51m Hc for the Sun center at zero geocentric altitude.
So, as I see this - the table in the Raft Book was calculated (or most probably -borrowed somewhere) with more corrections in mind.
Yes, a distressed cook in a life raft would be happy with just any means of knowing his position/progress to the rescue, but the table could be made better: it should include the azimuths of the sunrise/sunset points and Sun culmination times. The latter leads me to another question I will ask separately.