You're quite right Matt. What I failed to state was, that the maximum range, IIRC, was 150 to 200m in good, clear air, without any haze or moisture. Even then, the resolution, as you quite rightly pointed out, was not at all good, with anything at that range that was visible, being just a blur of shape and shadow.
The best results I seem to recall, were around 75 metres, and even then, the image was far from sharp or clear. The equipment had, we were told, been manufactuted in the mid-fifties, and was not that different from the early types used during WW2. BTW, the reason for using this at the time (late 70's), was to simulate the use of captured, 'second rate' equipment on a particular exercise. I have to admit at a little cheating, and collecting some Int by using the 'Starlight' 'scope I'd hidden in my Bergen! Who cares who wins, as long as it's me!!