On 2019-07-27 06:54, Alois Treindl wrote:
On 27.07.19 05:16, David Patte wrote:
For my products I use an algorithm (Meeus; Astronomical Algorithms 1998) to 'predict' deltaT into the future. Does anyone have a good source for a more recent algorithm that takes into account IERS values since 1998?
In Swiss Ephemeris, we have an implementation of delta T which tries to be state of the art.
See documentation here https://www.astro.com/swisseph/swephprg.htm#_Toc11319101
and source code here https://www.astro.com/ftp/swisseph/src/
The delta T source code is in file swephlib.c https://www.astro.com/ftp/swisseph/src/swephlib.c
The implementation is complicated by the fact that we try to be consistent with different versions of JPL ephemerides, which use different values for the Moon's tidal acceleration.
All the code of Swiss Ephemeris is published under GPL.
A commercial license is available for those who do keep their projects free of the obligations arising from Gnu public license,
Many developers who wish to promote using their code as a standard choose instead to license under the BSD or MIT licences as an option to or instead of the GPL, any mention of which deters most commercial licensees from even looking. Commercial licensees would rather deal with a few comprehensive sources than a bunch of little bits and pieces. As in all forms of commodity publishing, the issue is not really about buying, it is getting anyone interested in any of a particular author's works: the publishing businesses take a statistical shotgun approach, in the hopes that buyers will like a few works by some of their authors. -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada This email may be disturbing to some readers as it contains too much technical detail. Reader discretion is advised.