SIMBAD references

A new photographic C-M diagram for the globular cluster M 22 based on automatic plate measurements has been obtained. It reaches the main sequence turn-off point at V≃17.7mag , (B-V)≃0.75. Systematic difference in color with photometry by Cudworth (1986) has been revealed, which is probably due to insufficient account of color equation in that study. The position of the red giant branch bump in M 22 is at V ≃13.9mag , its magnitude differences with the horizontal branch and the turn-off point are normal for a cluster with intermediate metallicity. The comparison of our color-magnitude diagrams for M 22 and NGC 4833 has been undertaken. The difference of the color-magnitude diagram morphology between the two clusters is attributed to somewhat higher metallicity of M 22.