I'm wanting to place my 80mm refractor onto my dob to act as a super finder and auxillary RFT. Mounting will be easy as the dob OTA is enclosed in a box where it connects to the rocker so it will be mounted on this. I just need the correct hardware. Will these do...
Doppler - yes that is similar to the setup I have.
Astro, I tested out the theory by holding the 80mm tube to where I'd want to put it and ran into a few issues. You're correct where the eyepiece might end up too low, but a 90 deg diagonal offsets this somewhat. WHat Ive found is that the dewcap of the scope will end up too close to the existing finder and the focusing knobs might hit the edge of the rocker box when the main scope is pointed high. I could remove the existing finder and then placement of the 80mm will be easier. This particular dob is top heavy so it might even work in favour for the balance.