M15, AN ASTROMETRIC STANDARD FOR CCD OBSERVATIONS

CCD observations of stars in the region of the globular cluster M15 ha ve been used to obtain astrometric positions of 1092 stars in the cent ral part of the cluster within the FK5 system. The purpose of this cat alogue is to calibrate astrometrically CCD observations by means of me asuring the positions of stars in M15. The comparison with other catal ogues and with measurements of photographic plates of the central part of M15 indicates a mean accuracy of about 50 to 70 mas for each star of our catalogue.