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If it is a GSO 16" Dob it is actually a three strut system, with the strut ends having a steel fitting that bolts to the top and bottom sections in two places making ut a rigid connection. There are no poles with flattened end on that scope. I used to have one and the design has not changed. You can see it on the photos on the Andrews website. It is concerning that the original poster has been moving mirror without a good handle on the problem. I agree with John, that these are all made on the same machine and things like strut length do not vary. They do not need any adjustment to achieve focus, unless there is a manufacturing defect, which i have never heard of yet, or it was assembled or ham fisted adjusted out of spec. I lean towards the later.
Brian focusing on a tree is not the same as a star test, where the scope is effectively at infinity. I recall that my Televue Nagler 11mm ep always required alot of back focus on that scope and the extension tube was needed. I has a full set of GSO Superview EPs and they did not need extension. When you try to focus on a star and are racking the focuser inward is the star getting larger or smaller? If it is getting larger your going the wrong way
Last edited by glend; 02-07-2016 at 12:32 AM.
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