I have bought a couple gen-1's, seen a few other gen-1's , and a couple gen-2's and a '3--and if you want to see in the dark without being seen, save up $1400 or so for a head-mounted gen-2 1X monocular.
It will work the way you expect.
None of the gen-1's will work any better than a half-decent pair of 7x50 unpowered binoculars will at night.
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Gen-1's can work, they can be of entertaining and of some use as long as it's not tactical. The best way to use gen-1's is to get a 1X head-mounted unit (lower magnifications give clearer images), disable or turn off the scope-mounted illuminator (which is usually an easily-visible red LED) and spend a couple bucks and convert a 2-cell mag-light into an IR-LED flashlight. With this you can sneak around in the dark unseen, and still see usefully out to 50 yards perhaps.
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The main drawback to gen-1's is that they need illumination--and if you want to play "invisible man", you need to use IR light, and there is no cheap and easy way to make anything that will put out lots of focusable IR light. That's why you need a mag-light or similar: the flashlight reflector can focus the IR light WAY farther than it would normally go. So you use the "spotlight" setting for "distant" things, and the flood for up-close objects--where the spotlight would be too bright.
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Also: I would differ in opinion of the night-digital cameras--from what I have seen and heard, they only really work about as well as a gen-1. Their main advantage is that they are less-bulky than a videocamera with NV-attached but you [or police, as is usually the case] can still feed their image directly into a video recorder.
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