Abstract: The optical gun sight for daytime and nighttime use in which a reticle illumination system has two operation states, one with full range of illumination for shooting during daytime and dusk and the other with the range of illumination safe for the expensive image intensifier tube. When the optical arms sight is used under night vision conditions, switching means interlocked with the nighttime aiming unit automatically switches the reticle illumination system to a safe mode of illumination, such as low-intensity light or infrared light so that the expensive image intensifier tube is protected from accidental damage due to “burning” of the reticle.