As Dave says, full moon is going to be a bit flat. If you're after a really sharp result, your camera and lens must both be fully supported. To fill the frame, you're looking at around 15X magnification, so you're magnifying shake by the same amount.
I've had better luck with my Kowa spotting scope than my 1000mm mirror lens, just because the spotting scope is that much lighter and balances better on a single tripod with a camera attached than the mirror lens, which means less shake.
