Top left: the sky luminance (in cd m⁻²) as a function of zenith distance for an observer located at different distances from the center of the beam produced by a 54 m mirror at zenith. We assumed α = 0.0 and g = 0.6. Top right: the same as the top left but for α = 0.2. Bottom left: the same as the top left but for α = 0.8. Bottom right: the factor of the luminance increase when transitioning from α = 0.0 to α = 0.2.