[HenryNZ]

I have been involved with AP for a while now, and it has not been easy. I think I have finally tamed short focal length AP, but medium to long focal length AP remains problematic. Initially the problem has been with the mount and auto guiding, but after hyper tuning my NEQ6 and getting good OAG set up with a Lodestar, I think the problem with auto guiding is now behind me. I can now run PHD at 0.6 arc sec RMS error all night long using an OAG setup on my 6" RC at native 1370 mm focal length. You would think that the worst problem is over - but no! I have hit another stumbling block - the optics. To get the 1000+ mm focal length, I have a GSO 6" RC at f/9. Not only is the RC slow but it is also a bear to collimate. I could get semi-decent result when I was using small sensor like the Atik 314L which I now sold; but I simply could not get the stars round at the far edges / corners when using a DSLR.

I am seriously thinking about changing the RC to something a bit friendlier to use. But cannot decide which path to go down:

8" newtonian f/4 for 800 mm or f/5 for 1000 mm; or 10" newtonian f/4 for 1000mm
A 120 mm refractor at f/7.5 like SW120ED for 900 mm
A truss RC (smallest is 10" I think) at f/8 with fL 2000mm, hopefully easier to collimate as I think the primary and focuser are decoupled.

What do you use for 1000 mm + focal length and why?