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    Re: how are the tables for declination generated ? equation ? etc......
    From: Courtney Thomas
    Date: 2005 Feb 11, 22:26 -0500

    Thank you for your kind attention.
    I have a couple of old calculators laying about unused, e.g. TI-82 and
    HP-28C. Used to have an HP-97 that had programmable cards and a small
    printer. I have a small network at home with several machines running
    FreeBSD, Linux [several flavors], Novell, SCO, MS Windows [several
    flavors], etc..
    It'd be nice if I could prototype it on one of those with the intent on
    moving it to something portable later.
    I've done a little programming but it's not my trade. I have a
    familiarity with Fortran, Pascal, Basic, ASM, & C, and would be amenable
    to whichever you thought beneficial. I'd be even more pleased at using
    any available open code that you regard as being sufficiently accurate
    in it's output  :-)  and would prefer using open source compilers, etc..
    I'd like to start with an outline of the 'works', modularize it, and see
    how it goes. Though it's not something I need fully functional now,
    still I don't want it to become a career either.
    What's out there that can be bought and at what price ? If it's high
    then it would be worth the struggle, maybe, over some time if it doesn't
    require abandoning your life  :-)
    I really have little idea of the gravity of this undertaking being
    unfamiliar with the underlying math, and calculational constraints, etc..
    Your opinions/experience/guidance would be happily accepted.
    Frank Reed wrote:
    > Courtney, you wrote:
    > "I'm interested in possibly programming a calculator to handle some
    > navigation calculations to avoid carrying cumbersome tomes and am
    > consequently curious as to how astronomers come up with the declination
    > numbers, etc.."
    > There are parts of this that are relatively easy to calculate and parts
    > that are relatively difficult.
    > "Relatively easy": refraction and other altitude corrections, sight
    > reduction table equivalents, the equation of time, and the GHA/Dec of
    > the Sun and stars at moderate accuracy (a few minutes of arc).
    > "Relatively difficult": ephemerides for the Sun, Moon, planets, and
    > stars accurate to the nearest few tenths of a minute of arc or better.
    > "Calculating" these things on a traditional programmable calculator can
    > be a bit tricky since these generally have small amounts of RAM. On the
    > other hand, if you're willing to consider a more modern device --a
    > handheld computer, a palm device, you would probably have sufficient
    > memory to simply store the almanac data directly. This is not difficult,
    > and it would get you the same accuracy as in the published Nautical Almanac.
    > There are a thousand different ways you could go with this. Are you
    > interested in the coding? Or are you mostly interested in the final tool
    > (if so, there are many commercial options)? Do you want to start with a
    > few of the easy items? Or go for the whole ball of wax?
    > -FER
    > 42.0N 87.7W, or 41.4N 72.1W.
    > www.HistoricalAtlas.com/lunars
    s/v Mutiny
    Rhodes Bounty II
    lying Oriental, NC

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