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    Re: Long term almanacs
    From: Hewitt Schlereth
    Date: 2014 Jul 26, 13:21 -0700
    Francis, I'll wait for your long term almanac.

    The 1956-based long-term almanac I used in Commonsense Celestial Navigation is from Bowditch (c. 1966) which was public domain. 

    A more recent one based on 1972 is in Vol II, Appendix H, pp 687-692, of the1975 Bowditch. I used its quadrennial corrections when I made long-term almanacs for the sun and Aries by slicing out the daily columns from 4 NA's beginning with the leap-year 1976. 

    I mention the 1972 almanac because it  is more recent and may be better suited to your plan.

    The sliced-out sun almanac is in two of my books Latitude & Longitude by the Noon Sight; Celestial Navigation by Sun Lines. The Aries is in Celestial Navigation by Star Sights. I occasionally check them against the current NA when members post sight data and, like you, find small differences: 2' to 5'. 

    Since the Bowditch tables are public domain, I don't think there are any restrictions on their use.

    As far as the EQ of Time goes, I have a long-term almanac for the years 1876 thru 1879. Looking in it for 27 July, 1878, it gives 6m15s and says the quadrennial correction is zero. The NA for today gives 6m32s, a difference of 17s, not much for 34 quadrennial cycles.

    It's good to see you're getting on so well, Francis.

    Hewitt

    On Jul 25, 2014, at 10:26 PM, "Francis Upchurch" <NoReply_Upchurch@fer3.com> wrote:

    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

    Francis

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