Parallactic Angle

[Karen K]

There is an undocumented feature in PyEphem: the calculation of the parallactic angle of a heavenly body. Neither the PyEphem nor the WeeWX manual list it. I guess, few users will use it, but I was pointed to it in an issue in the Skyfield almanac extension GitHub repository. Usage is like this:

$almanac.moon.parallactic_angle

The parallactic angle is defined as the angle between two great circles: the circle through the body and the zenith and the circle through the body and the celestial poles.

Now, the Skyfield almanac extension includes this attribute, too.