def get_inst_filter_from_colname(column_name):
    """Get the instrument and filter name from a magnitude column string

    Parameters
    ----------
    column_name : str
        Magnitude column header from catalog (e.g. 'nircam_f444w_magnitude')

    Returns
    -------
    instrument : str
        Instrument name

    filten_name : str
        Filter name
    """
    parts = column_name.split('_')
    instrument = parts[0].lower()
    if instrument == 'guider':
        filter_name = ''
    else:
        filter_name = parts[1].lower()
    return instrument, filter_name