” Surely other way round? (longer exposures stabilise against seeing)? I use between 4 and 9 secs…” indeed but…
… to clarify I have to take short exposures to stop the guide camera saturating. I then use a low gain to prevent chasing the seeing.
By setting the guider aggression quite low it essentially needs to integrate up several exposures corrections before a sizable move is built up. Thus random excursions due to seeing get averaged out by only causing a series of small insignificant corrections. All the guider is doing is correcting for the slow drifts as the Paramount ME II with Protract does a good job on its own.
I agree a slit with it’s bipolar lobes is more difficult a guide challenge than the “hole” presented by a fibre. One reason I never felt happy with a Lhres III on a Barlowed Newtonian.
Regards Andrew