Shutter

Initially I considered to build bi-parting shutters, like those on Mount Palomar observatory, but I gave up because although they are simpler to make, they catch the wind and I had designed a large shutter opening (850mm). I decided to build it in two separate sections having a separate drop down flap at the bottom.  The top section runs in two aluminium tracks. The bottom section flaps outwards when I need to observe near the horizon.

The shutter is made from 1200 mm radius arcs and is 2 ply. The bracing in the shutter was made from pine wood . For the shutter skin I applied 3.2 mm thick plywood.

Shutter Tracks

The dome shutter rides on two parallel aluminium tracks.  Each 2.7 m length of 25 x 19.5 aluminium channel was screwed down against a 50 mm wide aluminium strip previously fastened against the 1100 mm radius dome arches to provide a smooth and firm base.

 At the end of each track is a small bolt that provides a shutter stop.

Weather Skirts

Two skirts made from 180 mm wide lengths of masonite are attached to the observatory. One is hung from the dome and the other is attached to the top of the base. This provides a trap to keep out blowing dust and rain. The dome skirt was attached after the dome was put on the base.