Accuracy of the analytical photon trajectory approximation (Eq. A.14). This figure is similar to Beloborodov (2002, Fig. 2) and shows contour lines (solid, dotted) of constant deviation δξ/ξ of the bending angle ξ = Ψ − α of the analytical approximation (Eq. A.14) to the exact solution (Eq. A.13). The black and purple shaded regions relate to the maximum radial emission angles, α_max and α_max^approx, for the exact and approximated case, respectively. The orange shaded area confines the region that can be occupied by a neutron star with M_NS = 1.4 M_⊙ (see, e.g., Steiner et al. 2013). Note that the y-axis of Beloborodov (2002, Fig. 2) actually begins at R_s/R = 0.01 and not at 0 as implied in their figure.