2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/221687Realistic modelling of radiation transfer in and from variable accretion disks around black holes requires the solution of the problem: find the constants of motion and equation of motion of a light-like geodesic connecting two arbitrary points in space. Here we give the complete solution of this problem in the Schwarzschild space-time.14 pages, 10 figures, type C orbits added, analytic solutions for time of flight of photons for all 3 types of orbits addedGeneral Relativity and Quantum CosmologyAstrophysicstext