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Originally Posted by glend
Mark, i will consider that. Doesn't aluminium flex more than steel when used in that sort of construction or does it have to be build thicker to compensate? What about thermal expansion?
I have emailed Teleskop-Express to see if they can provide a carbon tube for the MN190. The stock MN190 tube appears to be the same basic steel tube as the 8" Skywatcher f5 newt but with the baffling added. TS already provide a Skywatcher 8" f5 newt carbon tube at a reasonable price of about 400 euro. If i could get a MN190 carbon tube, with baffles, with focuser bore positioning correct, it seems ideal. Lighter in weight, more thermal stability, stiffer, etc
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Its worth asking but I have never heard of a carbon fibre version of the MN190 and those prices only come through economies of scale . Its not hard to make an aluminium tube as stiff - just a small increase in thickness as stiffness goes up by the cube root. Also the internal baffle rings that Gary makes are like sleeves with a 90 degree bend - they add a lot of stifness.
I dont think these days that an aluminium tube is much of a hindrance as subs are usually 5 minutes or less and you can check focus every so often . Anyways I don't think baffles do anything at all in a Newtonian type design - I think they are really there to appeal to the retractor community .Flocking is all that is really necessary . The primary mirror and secondary already give you a massive amount of baffling .
Still if you can get a carbon fibre mod it would be ideal .