Comparison between the average transit residuals for (21) Lutetia in the AL direction (x-axis) and the computed photocentre shift from the light scattering model (y-axis; left). The error bars represent the standard deviation of the residual across the transit (often smaller than the symbol size). The right panel shows the equivalent plot after correcting for the for the computed shift. The lines represent the displacement of each data point with respect to the left panel.