To say it straight away: I've been using the Walimex hammer out a single satisfactory image. The weather was mixed, partly sunny, partly cloudy. However, I did not use a tripod, turning neither in nor tripod. Instead, I am never gone to the shutter speed as a precaution under 1/2000 (trial basis for a few shots even to 1/8000) in order to avoid camera shake. My Experiences:
a) The exposure works flawlessly (aperture priority, since the aperture is fixed anyway)
b) The focusing is extremely difficult, even though the viewfinder of my Nikon is neither very small nor very dark. Excuse me, was not very dark. By the f8 Walimex the image is namely significantly darkened. My stand-denial made things of course not easy, because at 500mm but the viewfinder image wobbles considerably. I miss the good old cut image rangefinder.
c) If for focused times (but never what one is really sure, see above), the images are still only weak and blurred. Plenty of sunshine actually helps a little, but you should not expect miracles.
d) Should someone make the hope of being able to work around the problem by focusing-by incorporating just far enough distant objects with infinity focus: too early happy. I once trial focused on a 2-3 km distant wooded area and was still well ahead of the infinity focus. I do not know when this is reached. Perhaps, if one takes the Moon a bead? But wait, this is perhaps not so far-fetched, finally mirror Teles are mainly used in astrophotography. And since even on a large scale. So I assume that, at least for several light years away stars no individual focus more must be done. Well, if that is not good news out! :)
The bottom line is there from me for Walimex 500 / 8.0 only 1 star. Reason: Catastrophic manageability, sad picture result. Ultra Compact it may be, but who really wants a simple solution, an ordinary cheap 70-300mm telephoto zoom is should buy (there almost for the same price but without stabilizer incl. Autofocus) and make it an enlargement. The result is rather questionable, but the quality is not too bad as a ungecropptes Walimex Photo. I tested the Walimex at a D7000.
Note: Subsequent image processing I have not included in the vote - which has to seek my opinion in an objective review anything.