[XenonSurf]

In the past, I have read what B. Gruner, sub captain in the Pacific had to say about optics. He simply said that they were 'useless at night'. He didn't say that moonlight would enhance them in any way, so this would mean that moonlight is only a disadvantage for your sub in still waters and you have to be more careful.

In rough waters instead you would have a big advantage being able to see targets further away without them being able to spot you (or only when it's too late). But destroyers could fire fireworks in your direction if they suspect you close. But I haven't heard one example where the Japs were using this, they had very powerful glasses, but powerful also means: low contrast when looking far, less light capture and thus reduced capability.

Then, in theory, your sub could be spotted if the sun reflection from your optics are detected, but I have never heard that this was the reason for a detection.