Here are a couple of useful modifications to the door area, in addition to adding cross bracing to the door. I added aluminum brackets from the hinge to the adjacent post to take the door load off of the ABS plastic. Second, I got a piece of 1/8" thick ABS from Amazon and cut it to make a 6" wide "awning" over the door. This should keep rain from falling directly on the door seal.
BEWARE THE DOOR LATCH. If you have a door latch like the one shown, be aware that you can become locked out of your observatory, regardless of the key status. The small loop at the bottom of the latch will lock the door when it moves just a bit to the left and lock it open when it moves to the right. This happened to me the other night and fortunately the shutter was open, so with two step ladders, I was able to climb inside. I don't know how I would have proceeded with the shutter down and unable to be opened from the outside with the shutter motor drive in place. I initially tried using ths copper wire shown to keep it from locking closed but it started locking open SO I took it apart and removed the internal locking piece shown at the left in the second picture. This solves the problem and the external lock still works fine.