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    Re: almanac software
    From: George Huxtable
    Date: 2002 Mar 9, 06:37 +0000

    >At 6:54 PM +0000 3/8/02, Herbert Prinz wrote:
    >>Where commercial computer programs are concerned, this is mostly a
    >>thing of the
    >>past when computers were so slow and small that one had to make compromises.
    >>Nowadays, when all almanac programs come on CD roms and need 64 MB of memory
    >>just to bring the first window onto the screen, there is very little
    >>justification for truncating the theory of the moon after 200 terms.
    > Some of us (Jay and I, at least!) are still producing
    >commercial almanac software for platforms that don't have CD drives
    >or 64 MB of memory!
    It really depends what you are running the program on, and for. I have
    implemented a program for positions of Sun, Moon, 4 planets, and the
    almanac-stars. The results appear never to exceed 0.2 minutes of arc
    divergence from the nautical almanac, and this I maintain is adequate for
    all navigational purposes. Good for the next 50 years, if delta-t is
    updated from time to time. This has been crammed into 16 kilobytes of
    memory on a Casio programmable pocket-calculator, now sadly unavailable.
    But it's dreadfully slow: 5 minutes to get coordinates for the Moon, or
    Jupiter or Saturn, which are the worst-cases.
    George Huxtable.
    George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    Tel. 01865 820222 or (int.) +44 1865 820222.

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