3 ms·
Good question! I use Skyfield library for my project, it does require downloading NASA ephemeris, but it is only <200MB, unless you want a very long time period
by d_silin 3y ago
Good question! I use Skyfield library for my project, it does require downloading NASA ephemeris, but it is only <200MB, unless you want a very long time period and you need to do it once every few years.
(DE430 got published in 2014 and most current version is DE440, released in 2021.
- dsq 3y agoThat's what I thought must be necessary, thank you.
- mturmon 3y agoIt may be worth adding that the planetary ephemeris are computed by NASA (JPL) by integrating the equations of motion forward in time numerically. Then the results (e.g. planet centroid as a function of time) are encoded in a file, as noted above. That file is then read by the ephemeris software to obtain the position at the desired time. I haven’t checked in a few years, but there used to be multiple files to choose from depending on the time range you needed to cover. It’s free — “your taxpayer dollars at work.”