Ok,thanks Alex
This thread is bringing relief to my back pocket!,I was looking at buying a WO megrez 72
As,I thought the F 7.7 vixen was un- useable.
I will be using a Vixen 103 F 7.7 ED for main scope.
When I did use a Orion auto guider we just could not find many guide stars,I suspect the settings had been set for a shorter focal length scope-the owner used a megrez 66,so his auto guider was set for it-it worked fine.
But we did not change any settings on his auto guider whwn we put it on F 7.7 scope,so may be that was why we had issues finding stars.
Thanks for help
,saved me $600!
Chris