Here's an image of my observatory/shed. On the right is an image while in use. The observatory is about 11' 8" x 10' 6". Inside is mounted a Losmandy G11 head on a permanent concrete pier that is 10" in diameter. On the eq head is mounted an 8" newtonian and a 4" refractor guidescope. There is a regular door (with the x-shaped decor), and there is a door immediately to the right that folds down as a ramp (note the hinges on the bottom). The ramp is intended to allow my 20" scope to be rolled in and out completely assembled. For now, I have been storing the lawnmower instead in the storage area. The observatory is not quite complete. It lacks shutters, some additional trim-work, and some work on the inside. It is useable and makes a good spur-of-the-moment observing setup.
Here's are a couple of images of the pier. It is a concrete pier cast in sonotubing. The diameter is 10" and 14" at the botton. The footing in the ground is about a ton of concrete all mixed by hand. The g11 is attached by a bolt set in the concrete while drying.