Returns a pair of PyEphem-compatible coordinate strings (Ra, Dec).

        If the star has no coordinates in GCVS (there are such cases), a pair
        of None values is returned.

def parse_coordinates(self, coords_str):
        """
        Returns a pair of PyEphem-compatible coordinate strings (Ra, Dec).

        If the star has no coordinates in GCVS (there are such cases), a pair
        of None values is returned.
        """
        if coords_str.strip() == '':
            return (None, None)
        ra = '%s:%s:%s' % (coords_str[0:2], coords_str[2:4], coords_str[4:8])
        dec = '%s:%s:%s' % (coords_str[8:11], coords_str[11:13], coords_str[13:15])
        return (ra, dec)