Set up the DMK to test again with the Fujinon 75mm f/1.8, pointed at Sirius and slew around, I found that many stars can be seen despite the super foggy sky, transparency is less than 1/10, I would rate. I can see 3-4 stars only despite Orion was hanging out there.
I estimated that it shows more than my 10x50 binocular just the same sky.
Exposure was 1s, 3s will saturate the whole screen, 0 gain.
Focusing is extremely easy, one can turn down the exposure setting to say 1/30s or even faster, that would allow 30 fps, and push the gain up. I found the gain of this DMK is so powerful that exposure can be reduced quite a lot by pushing up the gain, yet the noise level is still under very very well control. This is very very useful for focusing.
2-3s exposure will already reveal the need of tracking, I just used my Unistar for the quick test.
Under such sky, I attempted to locate M41, but failed. I suspect it was there, but it was just some more stars but never a cluster, so it was never confirmed.
Very promising I would say, if it can ever be done successfully, a wider lens should be acquired for milky way shots, and f/3.3 reducer should be seriously considered as well.