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for true zero shift telescope you need to get rid of alot of things!. Isolation is the name of the game.
CF in conjunction with Al make for a good combination. CF to join the secondary mirror to the top tube ring, CF for the scope tube to the bottom scope ring, CF to join the bottom scope ring to the primary mirror fixture. Good design will limit the use of tube spacers to get focus. aka design the scope for your end game! that is pick what equipment your going to use and measure it exactly. make the actual scope adjustable to within a poofteenth of where you need to be for focus. that way you can place your sensor in the Critical Focus Zone without having to use 15cm of spacers to get there.
GSO RC scopes are what i call top of the bottom of the range similar to a EQ6pro but they are limited to what they are doing because they need to appeal to the whole community (silly if they didn't) that is, people with DSLRS, DSI's, SBIG's, OSC, Mono, AO, OAGs.
Hence why they make it there setups the way they do so that joe blogs with what ever can make it work! sweet made a sale! and why RCOS and DS instruments and the like are so damn expensive, they go the extra mile, and a basic assumption that your using high end gear on the scope which slots you in a limited range but within saying that gives you Aston Martin proformance!
Head to the Deep sky instruments web page and all their astro photos taken are with Dedicated CCD's, not to discourage would be buyers, but if your coming to buy something like that your normally not about to buy your first scope!
I myself am trying to source some GSO 6" RC mirrors and will be designing a little travel/photography scope. the aim of that game will be as light as possible with quality setup so i can whip it in my suite case and have something to go with! I have access to machines that are accurate to .001 mm yes thats 1 micron but my tolorances will not need to be this tight. and i will assure you that im not worrying about a 20 degree temperature differential (unless im in the sahara desert) so alot of my equipment will be ally with a bit of CF for asthetics
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