A CCD BVRI COLOR-MAGNITUDE STUDY OF THE GLOBULAR-CLUSTER NGC-5286

We present results of photoelectrically calibrated CCD BVRI photometry of 1391 stars in the globular cluster NGC 5286. The resulting color-m agnitude diagrams are the first CCD CMDs ever presented for this clust er, as well as the first CMDs for this cluster reaching beyond the mai n sequence turn-off. The subgiant, horizontal branch, and upper main s equence parts of the color-magnitude diagram are well represented. The level of the horizontal branch (near the RR Lyrae gap) is V = 16.m65, the main sequence turn-off is observed at V = 20.m05, (B - V) = 0.m73 , (V - R) = 0.m38, (V - I) = 0.m88. The 3.m4V difference between the t urn-off and the horizontal branch is typical of many globular clusters . Comparison with isochrones evidences for moderately high values of m etallicity and age of the cluster, in qualitative agreement with the a ge interpretation of the ''second parameter''.