The Gen. 2 Night vision devices are the biggest step in the night vision history between two generations.
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The useful range of Gen. 2 devices is up to 200 meters and beyond, when you have some light from the moon. For complete dark environments, good infrared illuminators are needed, which help you to recognize your observed object.
For the second generation, many different types of photocathodes are available, which can mostly be defined by price. In the 2nd generation of night vision devices also white phosphor photocathodes are available, which give you a black and white image. These tubes are one of the best on the market, and with them, you can get the most out of your device.
The Gen. 2 NV devices operate in a spectrum of up to 850nm, which is high enough, that the animals can't see when you turn a suitable illuminator on to illuminate it.
Be sure you don't expose the 2nd generation analog night vision devices to sunlight because it can damage the image-intensifier tube!