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Astronomical Algorithms, Tables of Meeus - Gil - 02-19-2023 12:27 AM
Question
Has somebody implemented, on a pocket calculator or computer, the tables given by Meeus at the end of his book Astronomical Algorithms, 1991, for the abridged version of VSOP87?
Regards,
Gil
RE: Astronomical Algorithms, Tables of Meeus - Felix Gross - 02-19-2023 11:48 AM
This may help
http://www.naughter.com/aa.html
I have not used that code but I want to (at one point...). Therefore, I would be interested at your feedback.
Felix
RE: Astronomical Algorithms, Tables of Meeus - PedroLeiva - 02-19-2023 12:20 PM
What an interesting project! I would like to ask for which calculator model are you planning to program? Pedro
RE: Astronomical Algorithms, Tables of Meeus - Gil - 02-19-2023 12:44 PM
The book is really a "must", with full detailed formulae and examples.
I used it to implement the formulae relative to my EPHEMERID.4XI.D.HP program (formerly for Earth ecliptic, nutation, Julian Dates, seasons) on my HP50G (EMU48 version).
Jean Meeus gives 3 ways to calculate the season.
I chose the intermediate one, that gives DT results within 50 seconds of precision.
I tried to use his abridged tables, but there I get some small differences with the results given by the author. It's strange, because normally all the working examples should be exact to the last but one digit.
Regards,
Gil
RE: Astronomical Algorithms, Tables of Meeus - Klaus - 02-20-2023 02:56 PM
Years ago I wrote a program on the HP50 that uses the Meeus shortened VSOP. Running time, for example for Venus ~2.5 min
Later, with NewRPL for the HP50, a program with the complete VSOP theory.
Running time, e.g. for Venus under 1 min
Programs are not mature and can still be optimized and run with an inserted SD card.
RE: Astronomical Algorithms, Tables of Meeus - Gil - 02-20-2023 03:21 PM
Interesting, indeed.
A lot of work, sure.
As I am no astronomer, I just used some of the given algorithms.
I used, in particular, the ones given for the axial tilt and tropical year.
Then I found some newer, for example contacting directly IMCCE.
When trying to improve the seasons calculations (my prior version being based on simplified Meeus' algorithms, with results correct to about 10-50"), now with tables given by Meeus at the end of his book, I mixep up different theories.
A very bad idea!
With this confusion, I could not find (of course) the exact result given by Meeus
(normally within 2-3" in within with apparent sun longitude = k×90) with his Bretagnon's simplified tables.
Fortunately, I understood my error... including two digits inversions.
Therefore, soon I will be able to publish a new version of EPHEMERID, with quite accurate seasons begins, in both TT/DT & UT, with an error of about 2-3".
Regards,
Gil
RE: Astronomical Algorithms, Tables of Meeus - HP67 - 02-20-2023 08:46 PM
I found the sunrise/sunset algorithm here https://edwilliams.org/sunrise_sunset_algorithm.htm
valuable and implemented it in FORTRAN IV, modern Fortran, and on the 50g.
I like Meeus' books, but I haven't coded from his examples.
The position of the moon looks interesting.
RE: Astronomical Algorithms, Tables of Meeus - Gil - 02-20-2023 09:34 PM
Have you checked with official, exact values as given for example by IMCEE?
Skimming through the formulae, it all seems to give a very rough idea of the exact sunrise and sunset tines, nothing then to be compared with what you might find in Jean Meeus' book Astronomical Algorithms.
Regards,. Gil