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This may be staledated but here is my response.
I have built 3 observatories to date. The first was a converted garden shed at home on a very thick 1 piece concrete floor. That worked fine.
Another was out in the country and that was an 8 inch steel tube, 5/6mm thick and 1.8 metres long set in a hole 800mm deep in the ground and set with rapid set concrete. Then pavers around the rest of the floor.
Worked fine and was easy to build.
The last was more sophisticated, a pier 800 x 800 x 800 deep. A 2nd slab 2m x 2m sitting on ground with building plastic and steel reo.
Then gravelly roadbase then finer paving roadbase and large pavers with a small gap at the slabs. Works fine, easy to lay looks good and is easy to maintain. No vibration issues.
The structure around it is not in contact with the floor so no wind induced vibrations.
I had read stories of one slab observatories where merely walking on the slab caused vibrations that wrecked images.
Frame is treated pine and L brackets and roofing screws. Cladding is Aircell insulbreak everywhere and colorbond Trimdek. Roof rolls off on 2 100x 50 x 4mm steel section and 8 wheels on top of the frame. Several trusses and light metal roof battens with the Insulbreak underneath.
Before summer I intend to install a solar powered fan to circulate air and maybe a whirlybird on the roof.
You need insulation and air circulation as you don't want your gear to fry in summer but you want rapid cooldown at nights.
Greg.
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