Unbelievable 1

I am an experienced photographer for more than thirty years. I am so used to handle large telephoto lenses.
I was very surprised to see the results for such small price.
This cheap lens can produce very sharp images if you know how to handle it right.
Mount it on a sturdy tripot, fix the right focus (this is not all to difficult after some Practise), and use a remote controler for the shutter. But above all, hang a ballast weight on the lens (for instance, a heavy binocular), just after the tripot mounting ring. This will prevent camera vibration due to the mirror and shutter movement.
The minimum focus distance can thus be reduced to 5m if you remove the screw under the rubber focus ring. The rubber can be fixed again with some super glue (cyanoacrylate).
To use the lens, the camera has to be put on AV mode and the exposure compensation normally be set on one stop below normal.
Of course this can manual-focus super telelens only be used with non moving objects.
Good luck.