SDSS DR13 Join

The table links the external catalogue original <code>source_id</code> (<code>original_ext_source_id</code>) to the corresponding additional numerical identifier (<code>clean_sdssdr13_oid</code>). Both <code>original_ext_source_id</code> and <code>clean_sdssdr13_oid</code> are present in the cross-match output tables (<code>sdssdr13_best_neighbour</code> and <code>sdssdr13_neighbourhood</code>).

However, in case there are suspected duplicates in the external catalogue, different <code>original_ext_source_id</code> will correspond to the same <code>clean_sdssdr13_oid</code>. In the cross-match output table only the <code>original_ext_source_id</code> of the source with the best astrometry among the suspected duplicates will be listed. In practice, users may use the <code>original_ext_source_id</code> in the original catalogue to find the matching source with the best astrometry.