Tonight I decided to shoot the moon, and I thought it would be fun to share my photos and the technique I used to get the images. This past evening was partly cloudy, so occasionally the moon would disappear behind the clouds, but it was clear enough to have several minutes to photograph the moon at a time.
I used my tripod and cable release so that I could have absolutely no motion in the camera while shooting. I wanted as much magnification as possible, so I used my 400mm lens with a 2x teleconverter. On my Canon EOS 50D camera, this is an effective 1280mm focal length (400mm x 2 x 1.6), so the moon was significantly large in the frame. The exposure that worked best was 1/20sec at f/11 (wide open) and ISO 100. The biggest challenge for me was getting proper focus. With the 2x converter on my 400mm lens, autofocus won't work, so I switched to live view mode and zoomed in on the craters of the moon. Then I manually focused the lens so that the craters were sharp. This I think is at least as effective as autofocus would be, aside from the fact that changing the focus also moves the lens slightly so it's hard to be sure you have proper focus until you let go of the lens and let the motion stop. And since the moon moves relative to the earth, it's always important to recompose your shot occasionally.