Experiments were performed with a closed-circuit TV system designed for applications involving nighttime viewing. Various lenses and recently improved TV camera tubes designed for low light levels can be used in the system. Aero-Ektar 24-inch f/6 and 12-inch f/2.5 lenses can be used with the RCA C-73410 image orthicon tube, the RCA C-73477 image intensifier orthicon tube, or the General Electric Z-5294 image orthicon tube, and a 10-inch-diameter Schmidt optical system can be used with the C-73477 tube. Information is displayed in final form on a 10-inch monitor screen at a luminance level adequate for conventional photography or for viewing without the necessity of prior dark adaptation of the eyes. The system was tested under low light level conditions on rocket flights, outdoor scenes, stars, and a resolution chart. The highest sensitivity was obtained with the Schmidt collector and the C-73477 tube, visibility thresholds being about the same as for a dark-adapted eye with a 7 x 50 binocular. The use of storage would increase the sensitivity beyond that of the dark-adapted eye. Under these moonlight to starlight conditions, the pictorial results indicate that these new camera tubes have a sensitivity increase of 20 to 100 over studio-type camera tubes.
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