Transient effects on the measured signal when changing between two grating positions performed during an engineering observation during OD 27 (see text). In the inset, comparison of the upward (blue) and downward (red) transients. The downward transient has been flipped to compare the two behaviours. For a regime of flux changes similar to the one found in the range observations, the two transients follow essentially the same behaviour. This justifies the choice of getting the median signal between up- and down-scan signals.