Telescope Primary Mirror Cell

A friend is building a 13.1" Newtonian telescope based on The Dobsonian Telescope by David Kriege and Richard Berry. This is the primary mirror cell based on the design in the book. The design was modified as needed to fit the telescope design and provide a couple of desired features. Due to the use of a light weight Colter mirror only 1.1" thick, construction with 3/4" square tubing provided sufficient strength. The cell is slightly larger than normal to accommodate an oversized mirror box. This required a support tab to be added for the top mirror post so that the post was properly positioned near the mirror. A 36" nylon wire tie was used for the mirror strap support. This was done because of the thin mirror and the need for an appropriately narrow mirror support strap. It was necessary to fabricate a mirror support hanger system that could be adjusted based on the mirrors axial position. On a Kriege mirror cell, the nylon/kevlar webbing mirror support strap is fastened to the frame and moves with the mirror axial position because it is flexible. The solid material strap required a different solution.