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A mate of mine and I were discussing this just last night, the thermal expansion/contraction of an aluminium tube the size that we would guestimate the GSO RC10 has would be, Given a 20°c temperature change, the worst case scenario (assuming very poor quality Aluminium) was a contraction 45 microns.
The F/8 optics of the GSO RC10 give a CFZ (Critical Focus Zone) of 140 microns. Hence, given you focus well at the start of the imaging run, and don't experience more than a 20°c drop in temperature during the imaging run, your focus would not noticeably drift over the course of the run... Its a different story when you're imaging with a fast system, Ie, an F/4 scope with a CFZ of 35 microns.. but with the slower ratio's, your focus would very rarely shift.. not before you hit the meridian and have to flip the mount anyway, at which point, how hard would it be to just touch up the focus before recommencing the run after the flip?
Yes, CF would be lighter, Yes it would likely (depending on quality/thickness etc) be more rigid.. As Peter said, It sure does look cool... but will it make a noticeable difference in focus during the course of your average imaging run... Probably not...
If we were talking about a fast refractor, MAYBE. but then, even the glass in the objective lens will contract/expand during big temperature changes, causing the focus point to shift anyway, regardless of what the OTA is made of...
Yes Saying "0 focus drift due to temperature is a great way to sell telescopes" In most cases, it actually MEANS nothing...
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