Elgin Observatory

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The observatory dome is constructed of polystyrene "bead-board"
coated with a thin layer of reinforced concrete "stucco".
The design is a simple geodesic dome ala Buckminster Fuller.
As constructed the building is 9-1/2 feet in diameter.

Footing and Telescope Base

The building footing and the telescope base are of poured concrete. The two foundations are separated as far as possible. The building foundation is a ring of the appropriate size placed just deep enough to be below the frost line. The telescope base is much deeper. The base rests on very firm soil (preferably bedrock). The telescope base is isolated from the building foundation and the observatory floor to prevent vibrations being transmitted to the telescope.

Floor and Walls

The building wall is framed with 2x4s. The exterior of the wall is covered with colored roofing metal. Floor joists are 2x8s on 16 inch centers. The floor is 5/8 inch plywood. The bottom plate is cut from pressure treated 2x6. The top plate is a double circle of 2x6. The floor is 18 inches below the top plate. This gives plenty of head height to the dome for a person 6 feet tall.

Dome

The dome design is a common geodesic dome. It is a combination of pentagons and hexagons. Each pentagon is surrounded by 5 hexagons. The dome is slightly greater than a hemisphere. The dome requires 6 pentagons, 10 hexagons and 5 half hexagons. As constructed, the sides of the polygons are 2 feet. This gives a dome diameter of 9-1/2 feet. It also matches the size of the foam board, available in 4x8 feet sheets.

To view the stereo-pair of the observatory, move back from your screen 4 - 5 feet, cross your eyes to register the two images; concentrate on the center image. 

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Other Builder's Comments/suggestions

Check out these [not all] foam dome projects:
Steve's dome in  Adelaide, South Australia
Here is another, this one is Steve's (from California)
Clement Svensson of Sweden has a new dome
Andy's Dome In Apache Junction AZ
Robin's Starshed in Brisbane Australia

Questions / Comments contact: garlitzj(at)eoni(dot)com
Joe Garlitz

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