Typical unassisted autoguiding quality in good seeing

The pixel scale in the above guide history plot is 3 arc sec/pixel (1.5"/pix binned 2X2), so an average error of +/- 0.06 pixels equates to just +/- 0.18 arc sec

No PEC, AO or ProTrack etc were used here, so.... it doesn't really get any better than this, at least not using mechanical mount driven autoguiding alone.

The above autoguiding produced this image: