Yeah my Powermate gets me to about f/22, which gets the image size about where I'd like it to be. Of course, on most nights the atmosphere has other ideas, at least for the C11...the 8" is much more usable on 7/10 nights I reckon.
I don't recall how I summoned up the mental fortitude to sit and calculate it, but one night I scribbled away and figured I wouldn't want to capture for more than about 35 seconds with my 224 and its 3.75 micron pixels before risking rotation spoiling the stack. This would be focal length dependent of course, as with my C11 that puts me under 0.12"/pixel.
Anyhow, with an aggressively chopped region of interest, the 224 (and no doubt your 185) will ramp up to between 100 and 150fps, giving me about 3000 frames per capture. If the sky is kind, the stack will be decently detailed but with some residual noise. That's where I find the derotation kicks in, as 6-8 of those can give a nice reduction in noise again. Hope this helps someone
