Hi Chip,
My experiences appear to be quite different from my highly light polluted suburban backyard. I have the 80x400mm CT-80 and also a William Optics 50x200mm guidescope. Also I have the ASI290MINI (2.9 micron) and a older Lodestar X2 (8.3 micron) guide cams. With either guidescope I see virtually no change in guiding when switching back and forth between cams. I thought the more modern ASI290 with a big change in arcsec/pixel would do something great but it did not.
However, when using either guide cam, there is an improvement in guiding when going from 50mm to 80mm aperture. I see about 0.2 to 0.3" improvement in guiding error. When cutting through local light pollution, the larger aperture lets me see smaller and crisper stars I can lock onto more easily. And my local seeing is not too great either, perhaps playing a factor.
I have not tested the above combinations in dark skies for comparison. So I can only say what has worked for me locally.
Regards,
John
