The ray plot representing evaluated (Q, t) points alongside the corresponding contributions. The data are the same as in the upper part of Fig. 7. The black diamonds show the effective values assigned to each (Q, t) point on a grid (thin blue horizontal and vertical lines). The rays from each diamond symbol point to the location of a pair of (Q, t) values that contribute to that point, and the circle size indicates the weight of the contribution. Since the best estimates of the nominal Q values indicated by the diamonds depend on the weights and distribution of the contributing pixels, these values fluctuate around the average value. In order to be able to represent data in the common t table for given Q values without introducing significant deformation of the curve, only points with values within a narrow `Q-grouping catch size' are accepted to enter the corresponding table. The checkerboard-type red/blue coloring is an aid to guide the eye only. The black dashed horizontal lines surrounded by a light blue zone (the Q-grouping catch size) indicate the Q values used to create the plots in Fig. 7. This type of plot allows for an easy assessment of the Q variation within each Q group and is a part of the standard report.