Thanks
Yeah the pully system works really well. And when the roof is closed, there's a couple of bolts that come through the walls of the observatory. I put a nut on each of those when it's closed, and it's not possible for anyone to open the roof from the outside.
I'll have to look again and see how long it takes to damped the vibrations. I'd heard that vibrations and poor seeing actually look almost identical, so I might think I'm just getting poor seeing, but it could be my iron monster lol.
That's good to know though, because yeah I'll give it a go as is first, and can always go for one of those ideas in the future as my skill improves too. I imagine it'll all be a pretty huge learning experience, with modifications along the way.
I'd love a "thud" instead of a "ring" if possible, so I imagine I'll go for adding more things to it at some point.
AHHHH! an aussie welder ... 
