Quote:
Originally Posted by Paul Haese
Further to your question re the truss employed. I have found no issues with this design at all. The 12" is using a Serrurier truss and it exhibits no flexure as described by Peter. I am not saying it is not a relevant concern; just that I have not seen anything in my long subs to demonstrate there would be a problem.
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I guarantee it's flexing....but probably not much at all.
The original design by Serrurier was based on the telescope weighting tonnes, hence no material on the planet was not going to sag...and Serrurier solution was indeed elegant. The instrument load was trivial in comparison.
Barnes Wallis employed a similar principle when he designed the 64meter Parked radio dish. Keeping a rigid hyperbolic shape on a dish that large, is nigh impossible...unless you work with gravity...which he did and employed a twin spiral structure that in bending under load, kept a hyperbolic shape but changed the focal point! Clever stuff!! (the receiver cage is easily moved in/out)
With amateur equipment loads, it's a moot point...well...up to a point. Instrument loads on amateur telescopes however are often not trivial when compared to the weight of the telescope...as is evident by having to toss the GSO focuser.
I'd suspect with modestly heavy cameras (STX16803+FW7+AOX or a similar FLI16803 system) it would be detectable.
My point being...it works, but it's not optimum.