Deep stacks of best-seeing images of HE 0047−1756 (74 images, with a total exposure time of 6.6 h), WG 0214−2105 (138 images, 12.3 h), DES 0407−5006 (82 images, 7.3 h), and 2M 1134−2103 (178 images, 15.8 h). The stars used to construct the PSF are circled and labeled in red, whereas the stars used for the night-to-night flux normalization are shown in green. The expanded boxes show single exposures of each lensed quasar in excellent seeing conditions, typically .