If you buy a 800mm / 500mm Mirror Lens at this price, then you should already know what kind of product you're getting. Real high-end recordings are not possible. Quick snapshots either. Both but I did not even expect. But with patience, practice and foresighted thinking (!) Are recordings with as an objective quite possible.
Next you need to consider in my opinion:
- You have to focus manually, which takes practice. One has the focus control behavior of lenses to meet.
- The focusing range is very small with two lenses. At 800mm it's crazy small, but it's there!
- I have a red dot sight on my camera for this lens. Otherwise look for you look stupid until you compose the image found.
- You need a tripod, clear anyway.
On cloudy days, the 500mm performs significantly better than the 800mm. With the 500mm sharp images are possible even in these conditions in the near and middle distance range. With the 800mm I in overcast conditions can make no satisfactory sharp images.
The situation is different when the sun shines. Here deliver both lenses for me satisfactory recordings; where the 500mm cut here much better than the 800mm.