After contemplating various complicated means of motorizing the roof; pulleys, etc., I settled on a simple commercial solution. Used a rack and pinion mechanism commonly used in Oman for steel sliding gates. Normally the motor housing rests on the ground, but in this case I had to have it installed on a steel bracket up near the top of the observatory wall. The rack is fixed to the rolling roof, hence it moves out of the view to the sky when the roof is open.