Hi Steffen, you are of course correct in saying that light pollution per se has little effect on being able to split tight binaries. At my place in Sydney I have, in addition to the LP, also localised seeing issues (like the oven exhaust from a takeaway next door).
At my dark site the only detriment to seeing are high atmospherics. The region is semi-arid and the ground doesn't hold on to the day's heat for very long. Temperature drops rapidly by 10+ degrees after sunset, and any wind quickly dies. Having said that, last week wasn't anywhere near perfect, both with seeing and being dark. There was quite a bit of fast moving cirrus cloud around during the day from an approaching cold front. There was also a bit of sky glow and a few remaining cirrus after dark. Even so, I was able to split 1" binaries and the SQM reading at midnight was 21.9.
As far as dew is concerned ... almost non-existent. As I mentioned above, it's semi-arid. On the coldest night (+3C) I noticed a sheen of moisture on my EP case but nowhere else, even though I don't even have a dew shield on the C11. The EP case is a yellow hard-case from Bunnings, and I have no idea how it attracted moisture, but nothing else. Maybe I was breathing over it
