Yes, Bert I totally agree. Ive not seen even much slower lenses that give pin sharp star images to the edge of the field like that. I predict that if mated to one of these cooled dedicated monochrome astro cameras and taken to a dark country site, several hours of Ha filtered imaging could well go far deeper then the UKST Ha survey. If ever I come into some money I will buy a sbig type camera. This
http://www.sbig.com/large_format/Pelly33.jpg
was taken with a Sbig camera and a F6 refractor and a red (not Ha ) filter., see
http://www.sbig.com/sbwhtmls/online.htm
Imagine same exposure times with the narrowband ha filter and the 300mm f2.8 lens. The mind boggles. Sadly the dedicated astro cameras are still far too expensive.
Note, a mate in Coonabarabran has a St8 I think, if ever I am able to visit him I will have to see about getting a canon adaptor for it and trying it out with the lens
Scott
Scott