Testing of the Canon FD 300mm f2.8

This is not a good test, but this is what I could do at the moment.  Dark sky should be where it shines.

The target object is the moon, and I've used a tele vue 5x before a star diagonal to push the power up...

I found that if I keep on indoor light on, the image will be totally washed out.  It seems like the lack of baffling is the killer of the contrast.  But for deep sky imaging at darker sky, it should be no problem?