Same as Fig. 1, but here the two images have been rotated to a mutual pupil angle and one has been subtracted from the other. This allows us to distinguish the systematicPSF differences more clearly, which include asymmetrically distributed PSF halos, different sharpness for the spider arms (probably due to different degrees of pupil smearing between α Pic and β Pic in the field-stabilised observations), and most critically for our purposes, a range of artefacts in the outer parts of the image domain, which are not in common in the β Pic and α Pic images.