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From: W. S. Murdoch, Polymers D&C (Kpt. 1027)
Subject: To Those Who Asked for TI-81 or 82 Sun Programs
I think I have mailed to everyone who asked for them copies of the text that I
submitted to Cruising World for the March 1996 article "A Sun Sight Reduction
Program for the TI-81 Calculator" and the booklet I have written "Sun Sight
Reduction with the TI-82 Calculator".  I was a little slow. I had to go to
Kinkos and have a few more run off.  If you don't get them in a week or two,
please ask again. I may have skipped over you.  My e-mail is here at work and
to save some time (this is not what I am paid to do) let me answer most of the
questions that I was asked in this note rather than replying individually.
The references for the mathematical methods for computing the GHA, declination
and semidiameter of the sun are at the end of both the article and the
booklet.  I don't have code for any of the PC languages or for spreadsheets.
It should not be hard to convert the TI-81 or TI-82 code that is in either the
article or the booklet.  The TI code looks like Basic.
The TI-81 does not have enough memory to do much more than the sun alone (and
still keep the good input and output formatting).  However, if you look
closely you can see that the GHA Aries is calculated as part of calculating
the GHA sun.  It would be possible to rewrite the program so that you could
reduce star sights by entering the SHA and declination of the star. These do
not change too rapidly, but they would have to be updated annually or so.  To
make room, something would have to be removed from the sun program, but life
is a set of choices.
The moon or planets require more memory than the TI-81 can provide.  The TI-82
has plenty of memory and is capable of much more than just sun sight
reductions to intercept and azimuth.
A couple of years ago I wrote a much longer TI-82 program that includes
almanacs for the sun, moon, four planets, and 93 stars.  It reduces single
sights to intercepts and azimuths and multiple sights to a lat/long fix.  It
calculates times of sunrise and sunset, handles great circle and Mercator
sailings, displays ephemeris data in both Nautical Almanac and Astronomical
Almanac formats, identifies unknown bodies, gives the data to set up a 2010D
starfinder, displays the altitude and azimuth of every body in its internal
almanac, etc.  The program fills the 28k calculator memory.  I wrote a small
book (180 typewritten pages) listing the program, providing test data and
examples, and describing how it works.  I have not been able to find a
publisher for it, but have been selling manuscript copies for $25 by word of
mouth and a classified ad in Ocean Navigator.

                  Bill Murdoch

   

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