I have a TAL-1 reflector and wouldn't mind using the OTA for a guidescope, has anyone used a reflector in this way? I only seem to find Refracting guidescopes?
I have seen a small newt on top of a larger newt used as either a guide or finder.
The only problem i can see would be image shift if the set up wasn't sturdy enough and or the optical axis moved as can be the case with newts. You also have to watch tube flexure.
This image shift happens if using a small S Cass or Mak Cass ontop of a larger scope.
The mirror focusing and image shift with these scopes can be a problem.
You can only give it a try.
You can get some pretty cheap chinese (Synta) Refractor OTA to use for guide scopes these days.