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Al, I've thought about trying something like this, not got around to it just yet...
My OTA is 16" in diameter and the primary mirror is 13.1", so there's a lot of clearance between the mirror and the inside of the tube - I reckon this is probably enough to keep the residual tube currents out of the optical path. Also I've spray-painted the interior of the OTA with matt black paint, my dodgy idea is that this paint is a little bit insulating, so the interior surface of this paint is likely to be closer to the temp of the air in the tube than the outside of the tube, but I have no way of measuring this as yet.
My temp probe on the tube is attached to the *outside* of the tube, which may not be the most relevant place. I'm considering attaching it to the inside of the tube so that I can see the real difference between the tube and the internal air.
regards, Bird
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