So I also have this ultra rare Pentax Ultra Achromatic Takumar f5.6 300mm sitting in my cupboard and I wondered how that would perform in UV.
Just opposite my house is that little mountain about 2 kilometers away and just ideal to take some shots from the upper window of the Windeck castle. It turned out that this lens is razor sharp and produces nice differentials (difference between the visible and the UV shot).
It was slightly sunny, around noon (not ideal for shooting UV actually).
The second shot is the differential and shows how the UV shot differs from teh visual obe. Colors were somewhat adjusted to taste.
The detail resolution is quite astonishing for that lens, which may be seen here on the explainatory plate which is about legible from 2ooo meters!
So I guess I like that lens!
Stay tuned, more will follow on that fascinating subject...
More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos