The same as in Figure 2, but showing the ratio of the diffuse sky luminance produced by the mirror to that of the full-Moon-lit sky (blue: mirror < Moon; red: mirror > Moon; white: mirror ≈ Moon). Left: perfectly absorbing surface (α = 0.0); Middle: typical ground albedo of (α = 0.2). Right: highly reflective snow-covered surface (α = 0.8). From top to bottom, the observer is located at horizontal distances of 5.4, 14.1, and 34.1 km from the axis of the light cone, all outside the directly illuminated area (radius 2.5 km).