'Calculate a sidereal time using a IAU precession/nutation model.'

def _erfa_sidereal_time(self, model):

    from ..coordinates import Longitude
    erfa_function = model[u'function']
    erfa_parameters = [getattr(getattr(self, scale)._time, jd_part) for scale in model[u'scales'] for jd_part in (u'jd1', u'jd2')]
    sidereal_time = erfa_function(*erfa_parameters)
    return Longitude(sidereal_time, u.radian).to(u.hourangle)
