Hi Tony,
I predominately run the GEG in F/5.5 mode, but find I still need to bin 2x2 to get decent results. No binning results in ~1.2 arcsec/pix, a resolution I would rarely achieve from the observatory location - perhaps twice a year if lucky (and only when all planets are aligned and the wind is blowing in a westly direction at 10 knots).
F/4 delivers really nice views, but vignetting is too extreme on the STL11k. I've taken some flats to correct this, but seriously its not acceptable. The quantity of image processing through reduction/calibration is clearly not worth the effort in restoring the image. In particular, I found after the dark and flats are applied I still see gradients. I've taken multiple flats at a 30% pixel well count saturation (approx 15,000 for the KAI-11000 chip) and sigma rejected them. I know the flats and darks are of good quality and match the imaging train profile well, but it does not clean up the images as much as I'd like. Don't get me wrong, I could spend hours post processing to restore them, but I don't think thats ethically right. There comes a point where an image is too processed and not natural.
I've never tried F/6.5 as I don't feel the focal reduction is enough, but does depend on the object you intend to frame.
Ultimately you are right, from a SCT focal reducer perspective it is one of the best around. There are other options such as those from Optec
http://www.optecinc.com/optec_026.htm, however I've never used one. I've heard the AP telecompressor is fantastic -
http://www.astro-physics.com/product...hoto_acc.htm#2
but again have not tested one.
Thanks for the feedback.
