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    Re: Calculators revisited (TI-86, HP 48gx)
    From: Bill Murdoch
    Date: 2000 Dec 10, 12:43 PM

    I chose the lower numbered TI-8something calculators to write programs for.
    They are widely available, cheap, and easily programmed with a Basic-like
    code.  There are lots of used ones around at about half retail price because
    many high schools require them for algebra and calculus classes, and the kids
    either dump them at year end or want to move up to a fancier models.
    
    I have written two programs both with 200 year +/- 0.1' almanacs.  One is a
    sun sight reduction program and the other is a full featured celestial
    navigation program.   A TI-81 version of the sun sight program was published
    by Cruising World, and I sold copies of TI-82 programs for both the sun sight
    and full celestial programs through a classified ad in Ocean Navigator for a
    few years.
    
    The biggest problem with these programs (and the reason that I quit
    advertising) was that the memory is RAM and can be lost.   Even with two
    separate batteries the programs can be accidentally erased when the batteries
    go flat.  Every month or two someone calls and says their batteries have gone
    flat and they have lost the program.
    
    The sun sight program is short enough that it can be punched back into the
    calculator in an hour.  That is inconvenient, but it is doable.  The full
    celestial program is 28k and takes a week to reprogram through the keyboard.
    That is not really practical.  Either program can be loaded into the
    calculator from a PC with a TIGraphlink cable in less than a minute, but if
    you have a PC with you, why is a calculator a particularly good thing?
    
    Right now I see the sun sight RAM program being a useful thing, but I have
    some doubts about a RAM full celestial navigation program.  Sun sights will
    check the GPS, and if necessary, get you where you are going without any hand
    calculations.  Why do you need more?
    
    I also think programming a calculator yourself is a good thing.  You can
    learn a lot about calculational astronomy and how the almanac is (actually
    was) produced.  If that interests you it could even be fun.
    
    Bill Murdoch
    

       
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