Not sure if I have posted this before, but Alice over at Alice's Astro Info has a wonderful article on Red Light and night vision. I recommend you head over and take a look. Basically she uses both primary and secondary sources (a few from the web so be careful) but the one from the U.S. Navy is quite interesting. She has links to her sources which helps immensely in following up with them. What does Alice find from going through these studies?
That red light is the best color to use. Specifically she states that it is the "rich ruby-red, not so much an orangey-red or pinky-red" that is the best. Also, that "you always need to be using the dimmest possible light to keep your night vision" and finally, that she, Alice, will "also probably only use them(her two red light sources) when I’m digging in my telescope bag or checking the site of my telescope set up to make sure I haven’t left anything behind. Don’t forget – humans have pretty good night vision – use it." Don't be afraid to get dark adapted and to use it . . . sometimes you just may not need a light to see that star chart, are only a very faint one at that. I recommend checking out Alice's site, especially if your in the Seattle area. She lists some good areas to view from up there. Also check out her table of contents, some decent articles are in there also. More to come shortly.