Lines: radial dependence of the boost factor ℬ for a central Lyα point source surrounding a uniform gas cloud of density n = 10² cm^-3 (black), n = 10³ cm^-3 (red), and n = 10⁴ cm^-4 (blue). When normalized to the cloud radius R, ℬ(r/R) does not depend on n. The grey line shows analytic solution from Dijkstra et al. (2006). The black line shows a case in which Lyα is produced uniformly throughout the cloud, and ℬ ~ 1, which shows that the calculations presented in the paper are quite accurate if Lyα is emitted uniformly throughout the cloud.