Top: δx as a function of X in units of HAWK-I pixels before S correction. Middle: as above but after S correction. Bottom: same as above but after S and FS corrections. In the left panels (from 1 to 4), we took 32 bins of 64 pixels each and computed the median of residuals in each bin (red squares). In the right panels (5), we show the periodogram with a period of 128 columns containing all the points plotted in the left panels. The dashed red lines show + 0.05, 0, and −0.05 HAWK-I pixel.