craftutils.fits_files.get_rotation_angle(header: <module 'astropy.io.fits.header' from '/home/docs/checkouts/readthedocs.org/user_builds/craft-optical-followup/envs/latest/lib/python3.8/site-packages/astropy/io/fits/header.py'>, astropy_units=False)

Special thanks to this StackExchange solution <https://math.stackexchange.com/questions/301319/derive-a-rotation-from-a-2d-rotation-matrix> :param header: :return theta: rotation angle, in degrees.