Comparison between some analytical curves of Fig. 9 (lines), and the results of an accurate ray-tracing (symbols) for an obstructed Wolter-I mirror with the same α₀ = 0.2 deg, R₀ = 139.6 mm, L = L ^∗  = 300 mm. The outer radius of blocking shell, , takes on the values 137.24, 138.29, and 138.55 mm, for Φ to match the values used to draw the analytical curves (but the unobstructed one). The accord between the formulae and the tracing is excellent within the statistical error.