Left: extraction of profiles, superimposed on the “master image” obtained for the R filter (innermost 40 × 40 pixels; N is up, E is left), together with contour plots; right: comparison of the averaged profile (thin continuous line; error bars on points are due to dispersion of values) with the average stellar PSF profile (thick continuous line), together with the residual points (subtraction of the stellar profile to the target profile; black filled dots).