Jimmy good on you for making your own observatory!
With respect to "destroying all the strength of the cylinder" I don't see that losing strength is a factor at all - the above mentioned example of a 2.5 metre tank is a >10,000 litre unit, it has VERY strong, thick, corrugated sides - by comparison some of the specific astro domes are made of exactly the same material, ie rotomoulded polyethylene, but are manufactured with much thinner walls
I guess if they work when designed to only hold their own weight, then a water tank conversion will be more than sufficient for the task since it's designed to contain 10,000+ kg's of water.
As for shelving - well they manage to mount them in the round domes ok, I think I'd just cut curved shelves out of ply and put them on brackets - who says shelves have to be straight?
As Omaroo said up above he's already seen someone who's done it, so we already have verification that it's not only theoretically possible, but in fact quite doable! (Any chance of some pics Omaroo?)
I hope to add my own version to the observatory community at some stage in the future. If & when I finally have the room, and the need to do it, I'll post the pics and let you all know!
