The catalog is the Saguaro Astronomy Catalog, combined with the Principal Catalog of Bright Galaxies (the PGC catalog), bundled into the MiniSAC scriptable database component (from ASCOM). You can make changes and additions to the source material and then re-generate the MiniSAC combined database by using the MiniSAC Catalog Maintenance Kit (from the ASCOM Site). The PGC data is included in the kit. I will update that kit for ASCOM if you send me a file with the correction(s) you make (and any additions) in the same format as Corrections(1.3). Be sure to follow the directions How to Add to Catalog.txt.