Blue Hills Observatory                                                                                (Click on images to enlarge)

The back of the dome showing the springs that help cushion lowering the roll over shutter.

The double pulley system for opening and closing the roll over shutter.

Detail of aluminum flashing to weather proof the roll over shutter, and showing one of the pulleys for opening and closing the shutter.

This illustrates the two height levels for the drop down shutter other than being lowered all the way down. It also shows the pulley for opening and closing the drop down shutter, and the slide bolt to fasten shut the shutter.

The roof of the observatory is sheathed with 3/4" plywood. An additional two layers of 3/4" plywood rings form a platform upon which the dome wheels are attached. A vertical band of 3.5" high galvanized sheet metal is the barrier that prevents water from getting past the outside skirting of the dome. The black band on top the sheet metal in this image is neoprene rubber. It sealed the observatory too well and caused rusting during Arizona's Monsoon season. After two years it broke down on its own and I never replaced it. The flow of air is better because it keeps things dryer. It lets more dust in but that is not a big problem. The surface of the plywood to which the dome wheels are attached is also covered with 26 gauge sheet metal.

The double wheel assembly I fabricated. It rides on both surfaces of 1/4" flat iron (that was arced to be concentric with the dome slit). The drop down shutter is hinged to the dome at the bottom. This double wheel assembly (there is also one on the other side) attaches the shutter to the dome at the top.

Dome electrical grounding   clamp.

The big day, June 30, 1989. The dome lifted and placed on top the building by Ace Sign Company from Prescott.

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