A cacade image intensifier viewer consisted of a catadioptric objective coupled to an extended red (S20) photocathode. The viewer components were designed to meet a performance criterion measured objectively by an optical transfer function. The eyepiece magnification was x7 to give the optimum transfer of of information between the image tube and the observer. The system performance at low light levels was limited by the statistical variation of photons at the photocathode and at high light levels (half moonlight and above) the performance was limited by the finite resolution of the viewing system.

A TV low light level system was constructed using a cascade image intensifier and an extended red (S20) photocathode, coupled by fibre-optic plates to the target of a vidicon camera. The remotely controlled camera was mounted on a pan-and-tilt head and located some distance away from a 9inch diplay monitor into which a video signal from the camera was fed. A simple joystick controlled the movement of the camera and further controls were provided to focus the camera and switch the power supply for the camera.