Ray fluence (defined by Equation (14)) on the sphere at infinity, corresponding to point emission in the frame of a massive test particle on the ISCO of a Kerr BH. The BH spin increases from top to bottom: a/M = 0, 0.7, 0.9, 0.99. Colors mark zones with fluence separated by powers of 1.7 (1.8 bottom panel), increasing from black to blue, mauve, white, cyan, green, gold, and red. The point (θ = 0, ϕ = 0) is antipodal to the position of the explosion. Strong peak near the center is produced by gravitational lensing, and the broad concentration to its left is caused by the motion of the emission frame. Projection is equal area, with horizontal lines marking constant rotational colatitude θ. These maps are obtained by a Monte Carlo procedure involving 10²³ trial rays, whose asymptotic direction is recorded in pixels of size (﹩{2}^{-8}\pi ,{2}^{-8}\pi /\sin \theta ﹩).