Observations of HD 66598 before and after telescope re-alignment. Top: differential delay of both sequences. For better readability, the Nov. 2011 sequence was shifted by –0.5 mm. Bottom: binned residuals before (dashed line and open squares) and after (solid line and filled circles) the alignment intervention. The binned residual dispersion decreases from 1.46 μm to 0.27 μm. Error bars are smaller than the symbol size.