One of the most important items of equipment American infantry have today are Night Vision Goggles (NVGs). These have been around for over three decades, but have gotten more powerful and cheaper in that time. The first night vision devices looked like a handheld telescope and used a light intensifier (a photocathode tube) to multiply available light several thousand times and show the user, on a tiny TV screen, a greenish, monochrome image of what was out there. On a clear night, with a full moon, you could make out a person at about 250 meters. With a quarter moon, the range for this was about 200 meters. With no moon (just starlight), it was about 150 meters and if it was cloudy, about a hundred meters. Second generation NVGs added another light amplification element (a micro channel plate) that boosted performance considerably. The range for identifying a man under different conditions was now 500, 450, 300 and 150 meters. Third generation NVGs, the most common available today, improves performance by adding a gallium arsenide coating to the photocathode tube. This improves performance to 650, 500, 375 and 200 meters. Most American troops are using third generation NVGs. But the fourth generation NVGs are now available. These don't improve detection range much, but do provide a much sharper image and better performance in very low light conditions (like inside a building, or even a cave.) Depending on whether it's a weapon sight or binoculars, a third generation NVG will cost you from two to five thousand dollars. A fourth generation unit costs 30-50 percent more. First generation units are available for under a thousand dollars. Despite the expense, many troops would like to upgrade to fourth generation equipment, mainly because depth perception and detail is better. This means there is less chance for friendly fire incidents during night time firefights. In the last decade, American troops have been practicing a lot at night using their NVGs and have learned that, while they can see at night, they cannot see nearly as clearly as they can in daylight. In combat, that clarity can be a matter of life or death.