Update June 22, 2004
A Design Change

I recently came to realize that the massive octagonal concrete foundation that I had planned (half-completed form above) would be overbuilding even by my standards. As a result, I re-designed the foundation. It now consists of eight pressure-treated 6x6 posts with 2x8 stringers. The posts will be set 30" deep (i.e., below the frost line) and encased in concrete so that they will not heave upward in freezing weather.
Above: the half-assembled foundation. It needs to be assembled in situ so that its precise location (centered on the northernmost pier bolt,) can be marked before the post holes are dug. Bear in mind as you look at this photo that 30 inches of each of these posts will be underground, and the completed foundation will be approximately the same height as the concrete telescope footer. This foundation is slightly smaller in diameter than the dome substructure that will rest on it so that there will be a slight overhang for aesthetic reasons.

Below: detail of one of the corners of the octagon. Each miter cut is 22-1/2°. There is also a 22-1/2° miter on the outside corners of the posts to facilitate the attachment of a decorative skirt.

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