Astrometry in the field of M 31.

We compare 5 reference astrometry catalogs relevant to the field of M 31: SAO, AGK3, ST Guide Star Catalog, Berkhuijsen et al. (1988), and Magnier et al. (1992). We find that the Berkhuijsen et al. catalog has a systematic error in both RA and DEC which may be as large as 10" across the range of their catalog. We present a correction from these coordinates to J2000.0 coordinates.