(Forgive any repeats, I'm doing this crit before reading other comments, so that I'm not influenced by them)
#1 The sharp focus should be on the canon, not the trees. If you had shot this with a wide-angle lens, it would've had a lot more impact.
#2 The front canon is blocking our view of the others. A higher viewpoint would've allowed a clear view of them all, + perhaps rotate the camera, trying various compositions to find the best one.
#3 I like this a lot. It contains an optical illusion that seems to stretch the RHS edge so that it appears taller than the LHS edge
This effect is kewl + exhibits a powerful demonstration of perspective + depth
The contrast is rather flat in the first two, but the third is much better.
All in all, well done on your first attempt!