Effect of the location of the reference star used for the r-band PSF modeling on the ghost strength. All stars used for the PSF modeling are plotted together. The disk position corresponds to the spatial offset of each star with respect to the center of the stacked images. Its size is proportional to the intensity of the star halo determined at a radius of 100′′, after a normalization of the profiles. Its color indicates the full width at half maximum (FWHM) of the star (with a color code given in the legend), to take into account the possible additional effect of the seeing.