now in 4th edition on amazon implemented on github by jfcarr in python, C, C++, Rust and other languages some history introduction on poliastro Steve Moshier's superb astronomical-almanac on Ubuntu , debian , his website , in javascript , gui Jean Meeus: pls refer here pmonstrasio Sean E Urban's book: astronomical almanac JPL Horizons provides interpolated results from spice kernels. The spice kernels contain blocks of interpolation coefficients using (usually if not always) Chebychev polynomials that allow spice users, other third party programs, and the Horizons website to calculate positions in-between the points where the coefficients are provided in the kernels. Elwood Downey of clearskyinstitute : XEphem github in python: From Brandon Rhodes: PyEphem, ( now depreciated ), based on XEphem starting 2007, and github repo, can be found in debian package study-pyephem and now replaced by Skyfield - SFAlmanac-Py3 For satellite: Briswe...