Hi Marna, greetings from the Critique Club!
First of all, don't be discouraged by your score / placing in this challenge. You can only do it better next Moon challenge :)
Composition
Nothing to be said here. You respected the rule of thirds, and although it was a very plain shot (no clouds, distinguishable features any than the moon) it was very effective.
Settings
It seems to my eye that the focus on the moon was a weeeeee bit off. I assume that you were at the long end of your lens (that has peak sharpness at f/11 @400mm), and it's very difficult to focus like this.
Since you had a tripod, you could have used live view and zoomed in to focus exactly where it would be sharp.
Processing
If you shot in RAW, you could try to use Recovery to gain some lost details on the white, and then selectively burn some parts of the image, so the craters would be enhanced.
If you have any questions feel free to contact me.
Regards,
Joao |