The 'secret' to success for my roll-off roof is in the wheels. I purchased steel casters from Graingers with grooves in them. Each caster is rated at 800 pounds (I estimate the roof weighs about 1,000 pounds). The casters roll on a 1/2 inch galvanized steel gas pipe which serves as an excellent guide. The gas pipe is anchored to the wood beams with nails that were inserted through holes drilled in the pipe with an electric drill. The casters 'bump' over the nail heads, but they are not serious obstructions.
The observatory is a true joy to use. It can be opened or shut in minutes and I have been known to close it down for an hour or so because of clouds with the telescope still tracking, and to go back and resume my work afterward.
