I was very curious to test my medium format Pentax 67 lens on an astronomy object. I couldn't wait until I got a clear sky and performed this test on the balcony without polar align. Very light polluted sky.
Here is the simple analyze I did:
http://www.astrofriend.eu/astronomy/...ax67-lens.html
I must say that it perform better than expected. It's a bit exiting with this medium format lens and I will later spend a night on some astronomy object at a place with darkness.
/Lars