Here you can find more star tests for this lens (and some others):
http://www.astrobin.com/search/?q=sa...se=5&license=6
It is interesting to see Bob Atkins website:
http://www.bobatkins.com/photography..._500_f6-3.html
The focus he managed to obtain with this lens is unnbelievably bad.. I think he made a mistake (or he didn't have enough patience to focus properly, and this is not easy task due to backlash in the focussing mechanism. The focussing when lens is pointing to the horizon may be disturbed by changing the direction... to the zenith for example.. because the corrector lens can potentially slide back.
This problem can be sorted out like on those images:
http://www.iceinspace.com.au/forum/a...e.php?a=142353
http://www.iceinspace.com.au/forum/a...e.php?a=143393
If the lens is used only for AP, this solution is not a problem, as the focussing must be done only once.. and then checked from time to time.
I focussed my Rubinar last year.. and the focus is still spot on.