Disk-integrated phase curves for F_I and F_Q/F_I for a Rayleigh-scattering atmosphere with ϖ = 1 and r_g = 1 and optical thicknesses from 0.1 to 10. Our PBMC calculations for n_ph = 10⁴ (red curves) are compared to the calculations by Buenzli & Schmid (2009) using a forward Monte Carlo algorithm (black curves) and at least 2 × 10⁶ photons per exit direction bin over the 30–120°α-range. Both sets of curves are nearly indistinguishable on the scale of the graph, even for the relatively small number of photon realisations used in our PBMC calculations.