Any observatory should have the minimum of thermal mass that can hold heat.
A large concrete slab is the worst option for a floor. It will equilibrate by dawn if you are lucky. This of course depends on climate.
I have a wood deck with gaps between the jarra slats. That way cool air comes from the ground and keeps the whole observatory about 7C below ambient during the day even in summer and full Sun!. It has a well insulated roof and IR reflecting paint on the outside.
At night with the ROR open it cools down to ambient in less than 30 minutes.
bert
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