The optical system of an image atmospheric Cherenkov telescopes (IACT) is significant element, the parameters of which - energy threshold, angular resolution, effective area, and field-of-view (FoV) define the telescope performance. The ray-tracing technique is widely used to simulate IACT not only in the design of optical systems but also in Monte Carlo simulations of air-shower events. Non-sequential ray-tracing technique is used for simulate optical system and light concentrators of IACT. This technique simulates multiple reflections on segmented mirrors of telescopes. For this purpose, open source software ROot-BAsed Simulator for ray Tracing (ROBAST) is used. The spot diagrams of photon intensity on focal plane for small IACTs with 8x8 degree field-of-view and 10 m2 reflector area are illustrated.
The above article has been retracted by the publisher because it contains significant overlap with manuscripts published in Astroparticle Physics and 32nd International Cosmic Ray Conference.