Cross-neighbours between SSA Source objects and the SDSS DR2 Contains information about the systems of field centres used in the SSA Cross-neighbours between SSA Source objects and the SDSS DR5 Survey field information for the SSA Contains merged sources for every field in the SSA Contains information about the Schmidt photographic surveys in the SSA Cross-neighbours between SSA Source objects and the 2MASS PSC Contains information about each survey plate measurement used in the SSA Contains individual plate detections for every plate in the SSA Contains a subset of the entries in Detection that are flagged as jun Cross-neighbours between SSA Source objects and the 2MASS XSC