CCD PHOTOMETRY OF THE OLD OPEN CLUSTER M67

We present a CCD photometric survey of the central one-half degree of the old open cluster, M67, in U, B, V, and I colors to magnitude V=20. Extensive comparison of our photometry with other published datasets shows excellent agreement, indicating that CCD photometry is capable o f producing a uniform set of measurements consistent with the photomet ric system defined primarily by the Landolt standard sequence. The col or-magnitude diagram of the cluster shows a well-defined main sequence extending at least to the limit of the photometry at M(v) = 10.55 and a substantial binary sequence. At least 38% of cluster stars are bina ries. The current generation of theoretical isochrones cannot be fit t o the observed sequences within the observational errors. We find a te ndency for more massive members of the cluster to be more centrally co ncentrated, along with a turnover in the cluster luminosity function a t low masses, which may be due to dynamical relaxation of the cluster. To the limit of our photometry, we find a mass of the cluster of 724 solar masses. In addition, we present a sample of stars of well-determ ined standard magnitudes that are suitable as photometric standards fo r further studies of this cluster and for general calibration of UBVI photometry using CCDs.