Solar Eclipse calculation routine #1078
Description
For the almanac calculations, currently Skyfield has method to calculate Lunar Eclipses, which both illustrates package capabilities and serves practical purpose to get details/analyse particular eclipse. Nevertheless, even more interesting case of Solar Eclipses calculation is missing in the package - wouldn't it be beneficial to have it included in the almanac calculations?
I created a pull request with example code for the Solar eclipses calculation:
#1076
The methodology is slightly more complicated than for Lunar Eclipses, but overall quite similar - it reuses the same function as for the Lunar Eclipses calculation to find the minimum angle for the earth-moon-sun system. It then checks three configuration cases, whether earth falls into penumbra, umbra or antumbra of the moon shadow. The routine then uses this information to determine the type of the Eclipse - Total/Hybrid, Partial, or Annular. Additionally, the routine determines the Magnitude and Obscurity for the eclipses by checking the overlap of the sun and moon radiuses from the point of the earth surface where eclipse is seen to be the largest.
The agreement of Solar Eclipses time, type, magnitude and obscurity is almost perfect as compared to the published sources (https://eclipse.gsfc.nasa.gov/solar.html).