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Should I try a spring-balanced Dob?

Started by drice, 08/29/2002 08:47PM
Posted 08/29/2002 08:47PM Opening Post
I'm making a 55cm f5 Dob from used parts. The gentleman who gave me the mirror and rocker boxes used them for an f4.2 mirror and told me he had some balance problems with it. I managed to get a used f5 Pegasus mirror and am afraid that with the longer OTA the balance problems will be worse. I am unable to modify the balance point of the scope due to the existing mirror and rocker boxes and would prefer not to use lots of counterweights. Balancing via springs rather than counterweights has been suggested, but I may need some help designing such a system. It would seem to me that something like the Orion "correctension" system would work, but that it could be modified by moving the top of the spring toward the mirror a bit, which would not only generate tension in the direction it is needed but also increase it as the scope is pointed nearer the horizon--exactly when it is needed to counteract the increasing leverage of a too-heavy secondary cage. But I don't know how big a spring to get, where to get them, or how far backward to displace the top end of the spring.

Does any of this sound feasible or even make any sense? Please give advice and, if you know of any, references to articles, if they exist.