M27 @ 7 x 300 seconds unguided - because due to clouds I could find no guide stars! so basically shooting through the clouds and hoping for the best.
Focal length is 600mm and focal ratio is f/3 with an Astro-Systeme Austria 0.73X Keller reducer.
f/3 is really great and allows my 5-minute subs to match 20-minutes with the AT90EDT. The downside is that the AT8IN is extremely sensitive to focuser tilt, flexure, sag, and mis-collimation. Stars are nowhere as consistently round as with the refractor, and I had to mod the AT8IN tube to tame the flexure and tube distortions - http://orlygoingthirty.blogspot.sg/2013 ... t-iii.html
Overall, using a newtonian for imaging is quite a hassle - but for that magical f/3 focal ratio. There is an alternative though - one of the various species of Takahashi Epsilon hyperbolic astrographs. These are f/2.8 to f/3.3 and hold collimation very well. They are significantly more expensive than the AT8IN however..
![[smilie=good-job.gif]](./images/smilies/good-job.gif "good-job")
