I got this lens as a gift, from a colleague who went onto retirement and moved towards the Atlantic coastline. I'm staying in old North and away from the sea.
The 500C I got is in pristine condition. It makes a better impression than the later 500N, but is bigger and does not focus as close.
Here are a few shots from this morning, all shot at f/8 of course, and 1/1000s. ISO was relatively high.
It is difficult to get a squirrel picture sharp, once you got it in focus, it has already moved and never stops moving anyway.
The parakeet shot is by itself uninteresting, but I observed they were mad at squirrels, probably because of egg theft [threat].
The brickwall shot is even more uninteresting, but those bricks are legacy from military engineer Vauban, who inspired many others. Vignetting is not very high, but constrast is relatively low, as usual with mirror lenses. The 500N is somewhat better I think, but I did not compare them so far.