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    Re: DIY long-term almanac for calculators
    From: Murray Peake
    Date: 2018 Jan 16, 02:47 -0800

    Hi Tony,

    calculator almanacs seem to have a history pretty much as long as electronic calculators. The easy solution now is to use an app on a smart phone - I have at least two such apps - the NAVIGATIONAL ALGORITHMS Nautical Almanac and the Navimatics Corporation CELESTIAL, both of which are excellent.

    If you want a conventional calculator implementation, looking around the web, I found celestia for TI-83 and planet_ti89 available as downloads. 
    If you want the fun (and learning experience) of writing your own, as Antoine says, Meeus is a good choice.

    There are also commercial solutions - StarPilot for TI-89 has built in almanacs. NavPac which is the computer solution used by the British navy, comes with printed coefficients for monthly and/or daily time scales which you could program on a calculator if you had the patience... NavPac is pretty expensive now, and only good for a 5 year span.

    The IMCCE website used to have an online interface which would accept a file of time values and return body coordinates at those times, which made it really easy to calculate your own Chebyshev coefficients - sadly it was shut down after a denial of service attack, and I'm not sure what is available now. You could also use MICA but it would be tedious to get lunar coordinates for a month, one point at a time.

    The more recent generations of calculators are basically hand-held computers with calculator buttons... It is possible to program in C and cross-compile ate least for TI-89 (with TIGCC) , HP 50g (with HPGCC3) and TI Nspire (with ndless-sdk). The TI-89 officially came with support for assembler programming (and hence C), HPGCC3 is a brilliant solution that patches the OS ROM and then generates small compiled code. ndless is a jaibreak solution but works well on my calculator. With a C cross-compiler, you can implement the code in Montenbruck's "Astronomy with a Personal Computer" which gives cut down versions of Brown's Lunar Theory and Newcomb's Planetary Theory, good to about an arc-second.

    The HP 50g also has a slot for SD cards which gives you 2GB of storage, so you could just store a text almanac on the card...

    Calculators are probably just about obsolete technology - the market seems to be largely driven by student/educational requirements now rather than technical usage, so there is more emphasis now on denying some functionality to prevent cheating in tests.

    There may not be much point in calculator solutions anymore, but it does provide a good deal of innocent fun.



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