Happy owner of a CDK 12.5 AND a 300mm (12") GSO RC (I know, chalk and cheese, but I really like my RC and love my little Planewave). The question I have relates to my recent experience adding the CDK to the observatory.
Bottom line, the PW is just incredible in terms of the technology AROUND the scope and stupidly easy to collimate, but it terms of "flat" image, to my poorly trained eye, they're pretty much equal - at least for APS-C sized sensors - when it comes to flatness (both are f8, both roughly 12", equiv focal lengths)
Which got me thinking about OTA #3 - ideally one day, I'd like to go bigger - ideally a 17" CDK (because they're so easy to work with) but perhaps a 16" GSO (suitably modified to include some of the automated heating/cooling smarts of the PW that I enjoy so much).
My question is "Can I/how do I compute the effective flat (or as good as) image circle for a given optical prescription and compare it to the CDK?"
I've read the ASA RC vs CDK white paper (aka the "we hate you Planewave" files) and it would seems that, even uncorrected, with a large enough aperture the field curvature for a 50mm diagonal sensor would be effectively equivalent to a CDK of a similar size (in so far as Joe Public wouldn't notice a difference in the final image and even the pixel peepers would need to, erm, peek).
Please don't misunderstand the post, I have a very real sense of the learning curve associated with trying to collimate an RC vs. the elegance of a CDK - I'm simply trying to get my head around the real-world technical differences and if I can save some short term pennies and go 16", I figure why not - I can always upgrade at a later date if money & passion permits.
Let the flames, begin!