Left column: for each observation, FWHM of the 1%, 5%, 50%, and 100% of the best frames in an observation compared to the FWHM of the corresponding “conventional” observation (see text for details). The solid line is unity, i.e. no improvement, while the dashed line shows the half of the conventional FWHM. Right column: similar to the left column, but showing the ratio between the shift-and-added and “conventional” FWHM. The red lines give the median (50%) and the inter-quartile points (25%, 75%) of each half-arc second bin. The plots are based on FWHM measurements of 7648 observations from the 2014 season at the DK154.