COMPOSITE M-V VERSUS (V-I)(0) DIAGRAM FOR TEMPLATE OPEN CLUSTERS

New CCD VI photometric data for 10 template open clusters with accurat ely determined fundamental parameters are presented. From the observed V versus V-I diagrams of the clusters, fiducial sequences have been d efined and transformed into the M-v versus (V-I), diagram by averaging sequences of template open clusters with similar ages. The resulting composite M-v versus (V-I)(O) diagram presents a homogeneous set of em pirical isochrones in the age range between 5 Myr and 4 Gyr. These emp irical isochrones show an overall very good agreement with those compu ted from stellar evolutionary models. Theoretical isochrones with mode rate overshooting fit the observed main sequences better than the cano nical ones for clusters older than 600 Myr. The present set of empiric al isochrones will be useful for the study of faint reddened open clus ters.