Here's the design outlined in gory detail.
305 diameter, 1700mm efl, f/5.6 (geometric). 146mm secondary, with baffle that makes it 49% obstruction - but this is an astrograph, not a planetary scope.
22mm unvignetted field, then a gradual drop towards the edge. System is designed to cover a large 35mm chip with diffraction limited spots 430 to 800 nm (well, NEARLY - it is just over 9 micron RMS at the edge of the 43mm circle; Airy disc size is 8.1 micron outlined as a black circle in spot diagram. But my chip has 9 micron pixels so I'm fine; kind of pixel limited instead if diffraction limited).
Design is all spherical, bar gentle elliptical primary (e=0.67) and should be
relatively easy to make. Especially if we mention that solution is based on off the shelf lenses, so corrector is in fact ready!
Another advantage is those lenses have an excellent broadband antireflection coating, something that is impossible to do in ATM environment.
It will have secondary mirror focusing, that was the easiest way to ensure zero flexure. Secondary assembly rides on 6 linear bearings ensuring no tilt during travel. Assembly is aluminium, but upper and lower assembly will be connected via unidirectional carbon tubes, minimizing the thermal expansion. In theory at least (mirrors will change focus themselves somewhat as they cycle, being Pyrex - but an internal thermometer will give readings to intelligent focuser program which should then track and refocus as temperature drifts).