while the corresponding F110W magnitudes are derived from the fiducial lines of the three sequences. The ASs are reduced by following the same procedure and by exploiting the same computer programs by Anderson and collaborators that we used for real stars. We calculated for ASs the same diagnostics of the photometric and astrometric quality derived for real stars and we selected a sample of well-measured ASs by using the same criteria described above for real stars.

To calculate the completeness that corresponds to the position and luminosity of each star we divided the field of view into five concentric annuli centred on the cluster center, and within each annulus we examined the AS results in five magnitude bins. We calculated the ratio of the well-measured recovered ASs to the input ASs in each of these 5$\times$5 grid points. The completeness associated to each star in the field of view is estimated by linearly interpolating among these grid points. We performed distinct completeness calculation for stars in each population.

The NIR CMD of NGC6752 {#sec:cmd}
======================

The $m_{\rm F160W}$ vs. $m_{\rm F110W}-m_{\rm F160W}$ CMD of all the stars in the WFC3/NIR field of view is plotted in Fig. \[fig:cmd\]. A visual 