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This is my latest scope. It was finished on 4/10/02 after 2 1/2 years of work, mostly on the mirror. It was a 12 inch port hole and was a real bear to figure. This scope is different than the rest of my scopes in that it has an open tube design. I decided to use 4 tubes instead of the usual truss system using 8 tubes. At $10.00 per tube, saving $40.00 was significant! The stability of the 4 tube arrangement seems fine. The mirror is a port hole glass and is 1 inch thick. I ground it to an f6; a good compromise between the more difficult f4 and the much longer f7 or f8. As it turned out f6 was a tuogh mirror to make, at least for me. The design is based on the Kreige/Berry book on dobsonian telescopes. The mirror box and rocker are ply; the mirror cell is steel angle and uses a 6 point suspension system.To help keep things in ballance, I use a single ring upper cage wich holds a helical focuser and curved spider. This design breaks down to fairly small packages when dissambled. All the pieces fit nicely in the trunk of my car. |
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