Theo's right... it all comes down to resolution of your imaging setup vs your guiding setup...
I've used OAG's and will be using one with my current setup.. I love them. You want to make sure your guide camera is sensitive! really sensitive... I'll be using a QHY5 in my Lumicon OAG for starters, and eventually moving to the Starlight Xpress Lodestar with the SX-AO unit..
I can tell you right now, the images I achieved with the OAG + C11 versus using a guide scope were tremendous.. Mind you I was attempting to guide my 2800mm focal length with a 400mm focal length guide setup.. Not the best setup.. Using the OAG my results were MUCH MUCH better than external guide scopes..
For what its worth, it makes setup easier too... Im lazy.. 2 scopes is a hassle!
