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differential expansion + flatteners
A number of CF double (serrurier style) RC truss designs such as A&M had an expansion joint where the main dovetail saddle plate connects to the middle aluminuim plate section and the rear plate section. Because the rear of the actual truss is CF there can be some effects I gather.
All of the CF truss assemblies I have built are like the RCOS configuration - which basically has honeycomb aluminium in the rear section and a CF truss in the front section. The rear cage is very rigid and can carry big loads. Focus seems to be stable in my 12"RC, even though it uses a pyrex mirror.
There was a 20 inch RC on a Cloudy Nights ATM (?Preston) thread a year or two back which utilised the double truss config. It was a very sophisticated design - seemingly very similar to the A&M truss design, and it had some sort of expabsion joint or similar at the saddle plate.
Re: flatteners
My 12RC uses a simple 2.7" doublet field flattener - these came from Star Instruments - who also made the mirrors. They supplied me with the lenses and I had the lens barrel made to suit. These cover an 11k chip nicely and are supposed to cover the 16803. So the 'build it yourself' option can work. Using the 2.7" threaded AP extension tubes to house the lenses is another option.
guy
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