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.