Quote Originally Posted by Markster View Post
I wonder how such a lense would do with astronomy shots... Anybody tried it, or know?
As far as know many telescopes are based on mirrors (Newton, Cassegrain, that stuff) and catadioptric lenses in photography are basically based on the same concepts.
In astrophotography everything is in focus so one should never get rings.

When I'm rich I'll certainly buy a Minolta RF 250/5.6 such a nice portable addition to my walk-around bag.
At the moment they are a bit too expensive:

http://www.ebay.it/itm/Minolta-RF-5-...item4850e73dbe (this probably is exaggerately expensive).

For most subjects (those without shining out-of-focus points) the circular effect is noticeable but not really disturbing.