I haven't really played under the sky, but found something even better.
A couple of years ago I went deer hunting with a couple of guys I game with. We took all our D&D stuff with us, so after hunting, we set up a large table inside my tent (it's pretty big) and played for hours using lanterns for light and propane heaters. It was great because there are no distractions, you play for a few hours, stop and cook a meal, and play some more, go on a hike, play some more, etc.
This past fall we did the same thing, except we didn't really even bother to hunt because we all decided we just wanted to play! So over the course of a weekend we ended up playing something like 20 hours, most of it D&D but we threw in some Star Wars for variety.