f.wales@glasgow.UUCP (f.wales) (03/09/84)
For a project, I am currently attempting to program an HP-41CX to compute the position of any stellar object, or any object in a solar orbit, and I am on the lookout for any references to efficient algorithms or data packing techniques which others performing similar computations may have found worthwhile -- not necessarily on a 41, but for any computer (or even just bare algorithms). I would be extremely grateful of any assistance which anyone could offer in this regard. For what it's worth, count me in a `yes' vote for net.micro.hp41. Thanks, RPN OK RULES!, Frank Wales (PPC #7931) /;^)
julian@deepthot.UUCP (Julian Davies) (03/19/84)
I suppose the phases of the moon might be computed reasonably with e sine curve, but for anything more precise, the moon is the worst object of all to compute positions of. Its motion is decidedly non-linear. good luck!
flinn@seismo.UUCP (E. A. Flinn) (03/19/84)
--- I just posted a note to net.micro, where I saw somebody saying that he had looked up the length of the lunar synodic month in a handbook, and then used that number to calculate phase of the moon at any other time. The Moon's orbit is seriously perturbed by gravitational attraction of other bodies in the solar system, and by its own and the other bodies' deviations from spherical symmetry, so the synodic period varies a good deal - 1% or so. You wouldn't have to extrapolate very many periods before you began to get the phases wrong. Serious lunar phase calculators should consider trying to get copies of the lunar ephemeris tapes from JPL or the University of Texas at Austin - the latter have been doing lunar laser ranging since 1979, and can tell you the position of the Moon to within a foot or so.
rivers@seismo.UUCP (Wilmer Rivers) (03/19/84)
Don't forget the U.S. Naval Observatory in Washington, D.C. Two of their main jobs are calculating ephimerides and answering inquiries from the public.
phil@unisoft.UUCP (Phil Ronzone) (03/20/84)
Want you need is an ephemeris. Large bookstore carry them (under astrology mostly! not usually atronomy!!). Good ones give refs/formulas.
gam@proper.UUCP (Gordon Moffett) (03/21/84)
# "Mathematical Astronomy with a pocket calculator" [sic] by Aubrey Jones, Halsted Press/John Wiley & Sons (1978). This is the only book I have found to provide formulas for calculating positions of planets. Unfortunately, I find the book tough reading, mainly because it assumes you are using an HP-25 (or HP-67 or HP-97) programmable calculator and without an understanding of that language the examples can be confusing. Oh, for completeness: ISBN 0 470 26552 3
richard@sequent.UUCP (03/21/84)
I'd appreciate it if someone could help me with the following: How does on compute what phase the mon will be in for any day of any year? I suppose this could be expressed in terms of degrees since the movement is sinusoidal. Any help out there? from the confused and bleeding fingertips of ...!sequent!richard
bill@utastro.UUCP (William H. Jefferys) (03/21/84)
> Want you need is an ephemeris. > Large bookstore carry them (under astrology mostly! not usually atronomy!!). > Good ones give refs/formulas. The Astronomical Almanac (Formerly American Ephemeris and Nautical Almanac) is available from Superintendent of Documents U. S. Government Printing Office Washington DC 20402 -- Bill Jefferys 8-% Astronomy Dept, University of Texas, Austin TX 78712 (USnail) {ihnp4,kpno,ctvax}!ut-sally!utastro!bill (uucp) utastro!bill@ut-ngp (ARPANET)
rck@iham1.UUCP (s dust) (03/22/84)
"Practical Astronomy with Your Calculator" by Peter Duffet-Smith (Cambridge Press?) Is another book that contains many astronomical algorithms in it. This book doesn't assume any particular calculator. The algorithms are also quite easy to coerce into your favorite programming language. R. C. Kukuk AT&T Bell Labs Naperville, Ill.