7 Conclusions

From our CCD photometry of 3620 stars in the globular cluster NGC 6723, we have determined several important parameters for this cluster. Its color excess is $E(B-V) =0.11\pm{}0.01$. The most plausible value of metallicity is $\rm [Fe/H]=-1.22\pm{}0.15$;even lower values are possible. Note that the method suggested by Sarajedini (1994) leads to an unacceptably low metallicity for NGC 6723. The apparent distance modulus of the cluster is (m-M)_V,6723=14.76. From isochrone analysis, we prefer the NGC 6752 age in the range between 15 and 16 Gyr, in the scale of Bergbusch & VandenBerg (1992). We have found an interesting separation of blue and red horizontal branches, near the region of the instability strip, by U magnitude in the $(U,\ U-B)$ diagram.

The shape and slope of the RGB in NGC 6723 which we derive are practically the same as in M 3. Remarkably, our value $\Delta{}V_{\rm TO}^{\rm HB}=3.50$ for NGC 6723 is almost exactly the same as those found by other authors for M 3 (3.52; Ferraro et al. 1996) and for M 5 (3.47; Sandquist et al. 1996). This similarity of the three clusters with intermediate morphology of the horizontal branch should be taken into account when analyzing the "second parameter'' problem.

Acknowledgements

We wish to thank Mr. Oleg Lahtionov for assistance during this study.