Quote:Sandwich carbon composite seems to me the best material for tubing, and carbon composite for truss.
Light, stiff, stable in temperature with near to zero CTE, (no focus change during night).
Here is my home made tube. The whole thing should be finished end of this year.
Quote:Sonotubes (concrete form tubes) are a good low cost solution, but you need to find quality tubing. Some of the stuff sold in the big box stores is too flimsy to work well.
Quote:Coming to ambient temp quickly is good, but materials that do that tend to also continue to cool and drop below ambient faster and farther than more insulating materials. As far as I can tell, this is as much of a problem as being above ambient.
Quote:For visual, focus shift is not an issue. The insulating properties of Carbon fiber maybe OK, in the refractor world and SCT worlds CFRP tubes mean slower cool down.Jon
Celestron 8SE Dobstuff 13.1": Swayze refigured Coulter mirror, 6 pt mirror cell (2 pt edge support) and CF focuser board made by me StarBlast 4.5 ST80/PortaMount II Zhumell 20x80/Oberwerk 15x70 on a Seronik-style tripod boom mount Hubble Optics 18 inch F/4 mirror.