Large-Scale Errors in CCD Photometry of M 67

摘要

The accuracy of new charge-coupled-device (CCD) photometry in the Vilnius system of the M67 cluster is analyzed. The observational material was obtained during six observing runs in 1994 to 2001 with the 1-meter telescope of the U.S. Naval Observatory Flagstaff Station. The main task was to establish CCD standards of high accuracy and to eliminate large-scale errors from their CCD photometry. The authors compare their results with the published CCD photometric data in other photometric systems. The comparison reveals considerable systematic errors in some datasets. (4 figures, 3 refs.).