The C-M Diagram of the Globular Cluster, NGC 6752

The BV-photographic photometry was made for 1714 stars (V<19.5) in NGC 6752. The C-M diagram of this cluster shows an unusually extended blue horizontal branch (V=13.5-17.8) with a wide gap (V=16-16.7) and the well defined giant branch with gaps at V=13.85 and 16.2. The turnoff point is defined at V=17.25+-0.15 and (B-V)=0.46+-0.02. If we take V_HB=13.85 for NGC 6752, then Delta V=2.80, (B-V)_0,g=0.76 and Delta V_TO=3.40 and the chemical abundance is estimated to be [Fe/H]=-1.67 or Z=4.3*10^-4 and Y=0.26. Some other physical parameters of this cluster are derived and compared with those for the well observed clusters M3, M13, M15 and M92.