Well, in a survival situation, it's generally best to start setting camp no later than half between noon and the horizon. If you have to move, it better be good. Then you use that flashlight and pray for a full moon and no clouds (best in winter).<br><br>In the desert, so long as there is no cloud cover, from the one time I've been in one, once my eyes were adapted, I could see fine from jsut the stars and a sliver of moon. At least well enough to not walk into anything like prickly pears, and my staff scouted two feet in front of me, so....<br><br>However, I also do some amature astronomy. I can tell you all kinds of things about white light and dark adapted eyes. Some of those memories make my eyes water just to think about. Red or green filters are the best bet, especially a weaker light with a green filter. Your eyes have better ability to see green, so you can use a lower power bulb for the same loss of night vision and longer battery life. Mine also seem to come back faster from a green of intensity X than from a red of intensity X, even if they hit your eyes just as hard. For moving about, amber is a good choice. Not as good as red, but you can see blood in it, and it penetrates the night further, IME.