This figure illustrates the a posteriori procedure applied to the raw PM measurement for field F2. Panels (a) and (b) show that corrected PMs (in units of mas yr⁻¹) do not suffer from systematic effects as a function of stellar colour. Similarly, panels (c) and (d) show that corrected PMs do not suffer from systematic effects as a function of stellar magnitude. In panels (e) and (f), we report the maps of the locally measured mean raw PM components of cluster members. Specifically, the deviation along μ_αcos δ is in panel (e), and the deviation along μ_δ is in panels (f). Each star is colour-coded according as shown by the vertical bar to the immediate right of panel (f). Panels (g) and (h) show the maps of the locally measured mean corrected PM of cluster members. We applied the same colour-scheme as in panels (e) and (f). Panel (i) shows the corrected proper motion diagram. Finally, panel (j) shows the corrected proper motion error in function of the F606W magnitude.