At the magnification provided by 2400mm, keeping the moon in the frame (without a tracking mount) is problematic. The moon must be led by the right amount to be centered in the frame after the vibrations settle out.
Fortunately, it is easy to precisely center the moon during post-processing – as long no edges are clipped. The black border is easy to extend on any side.
Is this full-sized image sharp? Not especially so. The wide-open f/16 aperture has some diffraction impact, 2x extenders magnify aberrations, and worse is the atmospheric distortion.
Would I buy a $20,000 lens to photograph the moon? While the 2400mm focal length is difficult to obtain otherwise, no, I'm not that serious about photographing the moon. But if you have the lens, the moon makes a fun subject.
A larger version of this image is available here.