Write a catalog file of the likelihood region including
    membership properties.

    Parameters:
    -----------
    loglike : input loglikelihood object
    filename : output filename
    
    Returns:
    --------
    None

def write_membership(loglike,filename):
    """
    Write a catalog file of the likelihood region including
    membership properties.

    Parameters:
    -----------
    loglike : input loglikelihood object
    filename : output filename
    
    Returns:
    --------
    None
    """

    ra,dec = gal2cel(loglike.catalog.lon,loglike.catalog.lat)
        
    name_objid = loglike.config['catalog']['objid_field']
    name_mag_1 = loglike.config['catalog']['mag_1_field']
    name_mag_2 = loglike.config['catalog']['mag_2_field']
    name_mag_err_1 = loglike.config['catalog']['mag_err_1_field']
    name_mag_err_2 = loglike.config['catalog']['mag_err_2_field']

    # Angular and isochrone separations
    sep = angsep(loglike.source.lon,loglike.source.lat,
                 loglike.catalog.lon,loglike.catalog.lat)
    isosep = loglike.isochrone.separation(loglike.catalog.mag_1,loglike.catalog.mag_2)

    data = odict()
    data[name_objid] = loglike.catalog.objid
    data['GLON'] = loglike.catalog.lon
    data['GLAT'] = loglike.catalog.lat
    data['RA']   = ra
    data['DEC']  = dec
    data[name_mag_1] = loglike.catalog.mag_1
    data[name_mag_err_1] = loglike.catalog.mag_err_1
    data[name_mag_2] = loglike.catalog.mag_2
    data[name_mag_err_2] = loglike.catalog.mag_err_2
    data['COLOR'] = loglike.catalog.color
    data['ANGSEP'] = sep
    data['ISOSEP'] = isosep
    data['PROB'] = loglike.p

    # HIERARCH allows header keywords longer than 8 characters
    header = []
    for param,value in loglike.source.params.items():
        card = dict(name='HIERARCH %s'%param.upper(),
                    value=value.value,
                    comment=param)
        header.append(card)
    card = dict(name='HIERARCH %s'%'TS',value=loglike.ts(),
                comment='test statistic')
    header.append(card)
    card = dict(name='HIERARCH %s'%'TIMESTAMP',value=time.asctime(),
                comment='creation time')
    header.append(card)
    fitsio.write(filename,data,header=header,clobber=True)