I've found my way, for the first time, through Pix Insight, courtesy of some of Harry Page's beginner's tutorials, and done a repro of the pic posted above.
See here
http://astrob.in/full/7267/ for a full size image.
It's still just the 1 x 45 second sub, so no stacking was necessary.
I've been doing a side by side comparison with Peter Ward's amazingly exquisite shot of Eta Car on the Deep Space Images forum.
http://www.iceinspace.com.au/forum/s...t=88034&page=3 He used an Astro Physics 305 mm f/3.8 Astrograph and I gather that he used several hour's exposure. What surprised me then, was that his pic does not pic up very many more stars at all than my 45 seconds through a 5" refractor. However, his shot has far, far more nebulosity, and the image scale is a little different, so the stars stand out better.
I'm now waiting for clear skies to get some more subs.
Chris