V-band image of HE 0047-1756 obtained by stacking the 10 best seeing and sky background images (V-band template image). The quasar and stars, which we use as a constant reference and PSF model, are labelled. The double quasar is enlarged in the darker box. The field size is 8.5 arcmin ×8.8 arcmin. The stamps used for the kernel computation are defined as 17-pixel squares (see Sect. 4).