[The_bluester (Paul)]

The only thing you would have to watch there Alex is I reckon for an Espirit 150 you would still want an OAG even with the CEM70G. I reckon guiding something that long FL with a 120mm FL guidescope built into the puck would be a challenge. Though at least a big frac would have the advantage of internally stable optics. Anything with possible mirror movement would be a real hassle I reckon.

The common wisdom seems to be with good rigidity, the inbuilt guider should be good to something like 600-700mm focal length. The real selling point for me was that I am setting up two rigs and while I am imaging at 480mm FL it allowed me to get USB3 connectivity and better electronics integration while kicking the cost of a second OAG and guide cam down the road a bit. So long as the inbuilt guider turns out to be a good thing.