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More dome pics
A few more pics.
I projected a vertical laser line to mark out the cut lines for the aperture. Something like 2 days to mark it out and 20 minutes to do the cut!
The shutter (Mk II) comprises two curved plywood side pieces, spaced apart by three lengths of 10 mm threaded rod. I fixed 35 mm bearings to each end of each rod; these ride on aluminium strips fixed to the top of the aperture frame. The tracks are extended beyond the frame using 6 mm threaded rod as standoffs. This was a bit fiddly but it works well. I first tried thin plywood sheet as the shutter surface, but the join was unsuccessful. The final version uses 0.55 mm sign-white sheet metal. Since a full-length shutter can't be parked, the lower 0.5 m of the aperture is covered by a hinged shutter that doesn't normally need to be opened.
Chris
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