I decided to buy a Canon EF-400mm f/5.6L USM prime, and it seems that I will have a good time using this lens. I have taken a few photos of the moon, some with a 1.4X teleconverter attached to the lens, but the lens by itself is sufficient for moon shots like this one. I do need practice as you can tell by the overblown bright spots on the moon, but will do better next time by bringing the ISO down from 320 to 160, or going to f/11 or so instead of f/8.
400mm, at 100% crop.
I went to the local dumpster site to take some trash, and there were a few ravens around, and also a bald eagle on top of a tree about 50 yards away. I got just a little closer before it flew away.
Raven, close enough for a full frame:
Eagle, 66.66% crop (I believe):