Quote:
Originally Posted by Paul Haese
Ken and Andrew, perhaps you are misreading my comments here or I was not clear, but I think the truss is a great design. My GSO 12 has this very truss design (though not held together by a square connection in the middle) and it holds the imaging package very well. I have attached an image to illustrate the point. The shroud has no physical connection to the truss or acts as a restraint in anyway. It floats in a channel front and rear. To my eye it looks almost identical to the AP version and I am pleased to see that design is being used by a company such as AP.
|
Sorry Paul - I wasn't critiquing the design. As Ken has pointed out its a question of nomenclature - amateur designs don't need to consider the differential flexure problem because it can be effectively eliminated completely on 'small' telescopes like this. When you have a primary weighing a few tons, and a secondary cantilevered several metres away you have to accept that there is a lot of flexure, and that's where the Serrurier bit comes in to keep it all parallel.
However, I recall a bit of freeware years ago that would allow you to design a true Serrurier type truss for a scope. however it turns out Bunnings doesn't carry aluminium tube in diameters of sufficient variety for it to be practically useful.
Cheers
Andrew.