Ratios F_a,c/F_a,cs as a function of the stellar effective temperature. Results are shown for different values of the optical depth τ and effective radii of the gamma size distributions. Black line: a_eff = 25  μm,τ = 4, blue line: a_eff = 25  μm,τ = 0.5, red line: a_eff = 0.1  μm,τ = 4, green line: a_eff = 1  μm,τ = 4. Calculations using DISORT are denoted by solid lines, two-stream methods are marked by dashed lines.