knee.

The comparison between the observations and isochrones that account for the chemical composition of stars in NGC6752, demonstrates that the three sequences correspond to the three populations (A, B and C) identified along the brightest part of the MS, the SGB, and the RGB by Milone et al.(2013, see also Yong et al.2005, 2013).

The MS-B is significantly wider than both MS-A and MS-C. The fact that its stars exhibit a color spread that is larger than the broadening expected from photometric uncertainties alone, demonstrates that MS-B is not chemically homogeneous.

We find that the MS-A, MS-B and MS-C host 26.3$\pm$1.4%, 46.9$\pm$1.3% and 26.8$\pm$2.0%, respectively, of the total number of MS stars. These results, that we derived in a field of view located about 4.8 arcmin north-east from the cluster center, are similar to the relative numbers of stars in the population-A, B, and C estimated at various radial distances (Milone et al.2013; Nardiello et al.2015; Lee 2018). Hence, we confirm that there is no evidence for any strong radial gradients within $\sim$16 arcmin (i.e.$\sim$8.4 half-light radii) from the center of NGC6752.

The relative numbers of population-A, population-B, and population-C stars are almost constant along the entire interval that 