Hi Lee,
Good info from Jase and Dennis there....
The problem is that with nearly all newts is there is not enough backfocus to put a OAG in the image train and if there was I say you would experience vignetting. You would have to move your mirror up another 50-60mm to get focus. I have only started the last few months doing guided shots with the new newt and am using a 70mm guidescope. My only problem is flexure which I am slowly sorting out. But is the only way to go for you.
A good set of adjustable rings mounted on your 8" OTA to suit your ed80 and you`l be ready to give it a go...
Lots of work getting a setup spot on hey...
Now that my mirror no move onto reinforcing those tube rings!!!
Cheers Gary