This is a very unusual looking observatory. Just a couple of observations/ questions.
How do you intend to hold down your roof against high speed winds? I thought about this issue a lot when I built and designed my roll off roof. I have often seen a lot of these roofs rolling in a u channel, but thought that this even with lock downs is fraught with all sorts of problems. The largest of which is the roof flying off in heavy winds. Have you a solution?
The other thing that has me intrigued is the way you laid the roof sheets. I note the corrugations do not run down hill but instead run horizontally. This is certainly not the norm. How will the roof drain? Do you have a plan for this?
I do like the way you have kept the walls low. I found that having high walls is ok but is problematic for seeing all the sky.
Keep the images coming.