Hmmm still leaves the possibility of flexure entering the system. The whole idea is the hard fix the camera on the QSI. It was not that hard to focus the AOG for the 583 I had and the 683 I currently have. I used plenty of cable to do the focus adjustment and it can even be a little out of focus. Seems a little superfluous to me. Each to their own though.
I also have one hopefully arriving soon. Gary made a slight modification so that I can use it with my ST-i on the ONAG. If it works as expected I think it will prove to be the perfect answer to focusing the guide camera on the ONAG.
I don't have a QSI camera so I might be wrong in assuming that when normally focusing the guide camera in that particular set-up the guide camera will need to rotate to focus. I find that a real pain because I personally find that it's a lot easier to diagnose guiding problems when the guiding chip is oriented so that x=ra. The ONAG has a similar issue. Achieving good focus + camera orientation is nearly impossible. This clever focuser addresses both issues so, and I'll speal only for myself, it will be really good if it lives up to expectations.
I plan to try the SharpLock focusing method using the ONAG which will require starting with excellent focus - given that all the focusing corrections are based on subtle variations in the shape of the guide star. I do have a Borg helical focuser on the ONAG but that solution - whilst it works - has potential for quite a lot of flexure. This new focuser will be rock solid in comparison.