Top panel: one thousand averaged C_ℓ values for simulated light cones using the shell method with error bars (red curve) and corresponding prediction (dashed black curve). We simulate here a light cone between redshifts 0.2 and 0.3 in a sampling N_s = 512 and a number of shells N_shl = 250 to ensure a sufficient level of continuity in the density field. The spherical Nyquist mode is situated around ℓ_N ∼ 650 and represented by the vertical reference. Bottom panel: relative deviation in percent of the averaged predicted C_ℓ values with error bars in red.