that NGC6752 host three main populations of M dwarfs. Finally, we plot in the right panel of Fig. \[fig:ASs\] the average stellar completeness against $m_{\rm F160W}$.

![image](f2LR.ps){width="13.5cm"}

Comparison with theory {#subsec:theory}
----------------------

To characterize the three MSs of NGC6752 we compared the observed CMD with isochrones from the Dartmouth database (Dotter et al.2008) as shown in Fig. \[fig:iso\]. We assumed \[Fe/H\]=$-1.61$ from Yong et al.(2005), \[$\alpha$/Fe\]=0.4 and adopted the age, t=12.5 Gyr, distance modulus, (m$-$M)$_{0}$=12.95, and reddening E(B$-$V)=0.07 that provide the best fit with the data. The reddening has been converted into absorption in the F110W and F160W bands by using the relations: A$_{\rm F110W}$=1.016$\cdot$E(B$-$V) and A$_{\rm F160W}$=0.629$\cdot$E(B$-$V) kindly provided by Aaron Dotter (private communication). The values of reddening and distance are in agreement with those listed in the Harris(1996, updated as in 2010) catalog, while the age is consistent with previous estimate by Dotter et al.(2010). We assumed different helium contents for the three populations of NGC6752 of Y=0.246, Y=0.256, and Y=0.288, which are the values inferred by Milone et al.(2013, 2018) from multiple MSs and RGBs.

The best-fit isochrones are overimposed on the observed CMD plotted in the left panel of Fig. \[fig:iso\] and provide a poor fit 