The shutter frame was a challenge to design.  I wanted the shutter to roll back across the dome and also have the zenith unobstructed.  I designed the dome to house at least a 14-inch SCT OTA so I needed a shutter opening past zenith of 7 inches.  I decided to construct a 2-part shutter.  The lower part of the shutter was designed to slide in a grove in the shutter frame to "telescope" into the upper part of the main shutter.  To accommodate this I cut the arches for the shutter frame and laminated a strip of 1/4-inch plywood to the edge of the arches.  I covered the lower portion of this plywood strip with aluminum flashing.  The inner shutter door would slide against this flashing.  I then laminated a strip of 1/8-inch door skin to the first strip.  I cut a 1-inch section of this strip from the inside edge where the lower shutter would slide.  I then laminated another strip of 1/4-inch plywood, with flashing attached, to the top of the 1/8-inch strip.  This would give me a frame with a 1-inch wide grove for the lower shutter to slide in.