One of my dream climbs is to climb Snake Dike on Half Dome at night with a full moon.
Are there any special considerations for rock climbing at night beyond bringing headlamps and extra batteries and dressing warmer than normal?
Route finding might be a problem:
Take a good map and possibly a GPS for backup. Actually, I'd probably never go climbing an unknown route at night (YMMV), but this is much less of a problem if you have already been there.
Also, make sure the weather is going to be good. Any clouds will ruin your full moon. Also (depending on the season) the wall may be icy at night if it was wet during the day!
For unforeseen circumstances (stuck on the wall? Stuck at the summit?), take an emergency blanket, extra food and adequate water.
Finally, make sure everything you do is legal. Authorities don't like nonstandard hours.
Depends on your headlamp. I use a Petzl Ultra Vario headlamp for caving that can cast a beam 200m, so when I've got that on I can see pretty much the same as climbing during the day.
I've climbed at night before, there wasn't any real significant difference. We happened to be climbing during a full moon as well, and as soon as that moon came out it was very bright on that rock face, much brighter than down on the ground in the trees.
One thing we noticed climbing with headlamps, is holds are sometimes easier to find. Your lamp will cast a shadow behind the holds, making them stand out a lot more than during the day when the sun is beaming from above.
One other thing about climbing in the dark is you lose the sense of how high you are off the ground. Your belayer's light gets smaller and smaller, but you don't get the same sensation as you do during the day.
I think the greatest danger climbing at night, is falling rocks. You're not going to be able to see them coming, and if you do see them you aren't going to be able to react fast enough to get out of their way. I remember belaying at night and not knowing there was a rock falling until it hit the ground beside me, so keep your helmets on.