I'm in a new location where a dome observatory is necessary due to street lights so I am giving away my previous 12 foot (3.7 meter) square roll-off roof observatory. It's made of 2x4 and 4x4 lumber with wood panels. It uses light-weight custom fiberglass roof panels that hang on the side of the observatory when open. I had it on a concrete pad but you can use it on any type of floor/pad you want. The walls are 6 feet high with the roof peak about 6'4" above the floor.
It's yours for free, just come and pick it up.