The formula in The Modern Dobsonian for pole diameter is actual pole length divided by diameter should be about 80. Changing the thickness does not make a whole lot of differnce to stiffness compared to changing the diameter. 20mm poles are therefore ample for a 12" F5 scope . It is only supporting a top end weighing a handful of kg. I'd avoid 6 pole trusses though.
Mark
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Originally Posted by janoskiss
Found a local supplier for aluminium tubing to use for a 12" truss Dob (thanks Vermin!). For those who have done this before, what size tubes do you recommend for the truss poles? These are the sizes available from the supplier:
Outer diameter : wall thickness (in mm)
25 : 1.6
25 : 3.0
32 : 1.6
32 : 3.0
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