Example illustration of the effect of the rotation of the X-ray source. The dotted red curve shows the reflection spectrum computed with reflkerr_lp (i.e. for a static point-like source, at h = 2.) The dashed black and solid blue curves show the reflection spectra computed with reflkerr_elp with r_c = 0.2 and 1.5, respectively, in both h_min = h_hor and h_max = 2. In all three cases Γ = 2.6, ξ = 50, A_Fe = 9, i = 50°, a = 0.998, r_in = r_ISCO and ℛ = 1. The observed primary spectrum is the same in all three models and is shown by the dot-dashed black curve. The difference between the reflkerr_lp and the reflkerr_elp spectra is primarily due to the azimuthal motion of the emitting plasma in the latter, where V ≃ 0.1c for r_c = 0.2 and ≃0.8c for r_c = 1.5.