Initial positions and destinations of 40 000 rays at the entrance pupil (points) for a Wolter-I mirror shell with L = L ^∗ , and the angular parameters reported in the legend (Φ ≈ Ψ ≈ Σ). The radial scale has been expanded. Only rays that would have struck the primary mirror were traced. The limits of the regions of different vignetting (dashes) are computed from the vignetting coefficients.