I've done a bit of night shooting; we set up a few courses of fire, then shoot them repeatedly as the sun goes down. It's interesting to see how dark it can be, and still have effective sights (also, how dark it can be before night sights are more efective than fibre optics). Then, it gets to the point that you can see the target, but not the sights, then you can see nothing without a light. I prefer to go as long as possible without resorting to a light, if given a choice, but you can't always choose.