Back a little in time: When in 2012 I was able to acquire three prototypes of those lenses, made 1992, which came from the estate of the inventor, Richard Nye and his company, Nye Optical of La Mesa CA, I was very excited to find such lenses able to record in deep UV. But they turned out to be a bit tricky to convert and adapt to digital cameras. Now with mirrorless ones, it looked rather promising...
So, these scientific lenses Mr Nye invented and custom made, were for deep UV recording (capable to even work beyond 200nm, especially made to record the 121nm Lyman alpha lines, hence the name). It is a catoptric (reflex) Cassegrain design, which came in f2.8/200mm and f1.1/90mm (and some other) versions for full format cameras, but also for intensifier tubes and video cameras (25mm image circle, like the f1.1/90mm), with focusing from 250mm to infinity and some adjustable 50mm resp.18mm back focal length. And now I have them working on my Panasonic GH4 camera....
[click on image to see a larger one]
Inside the aluminum housing resides an about 25mm (1") thick quartz (ZERODUR most likely) mirror block, front aluminized plus a secondary mirror (most likely made of the same material) held by an adjustable metal "spider" in front of that first one. Quite built like a small 90mm diameter Cassegrain astronomical telescope.
DOF at one (1) meter (3ft) is as thin as a razor blade when using the Lyman Alpha f1.1/90mm lens and that doughnut shaped bokeh etc. makes it fun to use.
Here now a few images in visible light, UV will follow, weather permitting...
The very thin DOF of course generates those doughnut shaped bokeh bubbles, but by chosing a proper i.e. less noisy background it can be "tamed".
I have written about those lenses before HERE
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