toolbox.py 文件源码

def parallatic_angle(ha, dec, geolat):
    '''
    Parallactic angle of a source in degrees

    Parameters
    ----------
    ha : array_like
        Hour angle, in hours

    dec : float
        Declination, in degrees

    geolat : float
        Observatory declination, in degrees

    Returns
    -------
    pa : array_like
        Parallactic angle values
    '''
    pa = -np.arctan2(-np.sin(ha),
                     np.cos(dec) * np.tan(geolat) - np.sin(dec) * np.cos(ha))

    if (dec >= geolat):
        pa[ha < 0] += 360*units.degree

    return np.degrees(pa)