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Originally Posted by astrojase
CF expansion? Carbon fibre does not expand...negative coefficient of thermal expansion. Or rather, has a very very low expansion coefficient - depending on the type of weave and direction employed. I am suprised that you were able to measure it Brad! Well done!
Still, compared to aluminium or that sad excuse for metal that most ota's (including some of my own) are made of these days, any improvement is a bonus. Excellent post brad, thanks for the info! ;-)
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I should correct myself. My OTA has two T6-6061 Aluminium Dovetails and two Rings as well. The truss is fully CF.
Simple to measure, the secondary focuser has 1/40,000 of a inch encoder res. I then do a focusmax run at the start of the night (before cool down) and one after the temp is stable. Do this over a few nights and you can calculate it.
Cheers,
Brad