The multiangular photometry reduced from the lunar mare regions depicted in Fig. 1 as a function of the phase angle α. The opposition effect shows up as abrupt nonlinear brightening towards opposition. The viewing geometries of the AMIE lunar images are also depicted. Each geometry is fixed by three angles, for example, the angles of incidence and emergence (ι and ϵ) and the azimuth angle φ (that can be replaced by α).