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Originally Posted by Leif
This might be obvious to everyone, but even if you have a rock steady tripod, there is a limit to how much detail you can obtain with an unguided camera and lens, for the simple reason that the moon moves relative to the Earth. To get critical sharpness, you need a driven mounting (termed an equatorial mounting) that compensates for the Earth's rotation. (The motion of the moon relative to the stars is small relative to the motion of the stars.) One way to improve sharpness without using a driven mounting is to increase the film/sensor ISO to allow shorter exposures. (I've not done the numbers to work out what you can get away with.)
As an aside, many people think that the best time to photograph the moon is when it is full i.e. fully illuminated. That is not really true, as most of the detail is washed out, since the light hits the moon head on, and there are no shadows. More detail is seen when the moon is a crescent as seen in Don's photo. In the region between the light and dark areas, shadows pick out numerous craters, otherwise invisible in a full moon image. I've seen composite pictures of the moon made by combining photos taken at various phases, so as to show craters over the entire surface, and not just at the terminator.
Leif
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This makes a lot of sense and explains why I failed to get a sharper image by stopping down the lens. I noticed the moon moving remarkably fast needing camera and lens reposition every shot, 40-50 seconds or so. I predict 1/100 at ISO400 f6.3 is realistic for my next attempt.