Difference between the disk-integrated flux F computed using Eq. (14) and computed using the analytical expression for a sphere with a Lambertian reflecting surface and a geometric albedo A_G of 1.0 (see Stam et al. 2006, and Eq. (39)) as a function of the planetary phase angle α for various values of N_eq, the number of pixels along the planet equator. The difference has been normalized to A_G. The dotted line shows that N_eq increases with according to N_eq(α) = N_eq(0°)[1 + sin²(α/2)], with N_eq(0°) = 40.