A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Francis Upchurch
Date: 2014 Jul 25, 22:11 -0700
A question for a couple of sages, probably Geoffrey Kolbe and Hewitt Schlereth please.
For years, I've been using the small "one page" long term almanac from Hewitt's book as part of my minimilist Crash bag kit. Reduced, it is also small enough to fit on the curser of my Fuller slide rule. Despite the base year being 1956, using the quadrennial corrections, I usually get GHA correct +/- 2-5' and declination usually better than that. I've got Geof Kolbe's excellent book which should take me out well past my own terminal declination at 2050! (if I'm still wealding my sextant at 99, I'll accept a few minutes inaccuracy).
My question is, Geoff says in his book that this quad correction routine only works for up to 50 years, then goes off rapidly. Any ideas how long before Hewitt's one pager will no longer be usable? Otherwise, I suppose we could update the 1956 GHA and DEC numbers to say 2012 almanac and start again? Would that work using the same quad correction routine as described in Hewitt's book?
If the answer is yes, with your permission Hewitt, I may volunteer to put a new one pager table together base year 2012.(probably not until the winter though) (unless you want to update your own wonderful book?)
the other way to go for minimalist kit is the EQ of time/ declination table which I do for each year and stick on my slide rule.
Am I correct in thinking that EQoT does not change year on year (except for dates), but only declination requires the quad correction?
Best wishes to all