Before I built my obs I regularly set up with brilliant clear sky, got one sub and then it clouded over. I wait for an hour, still cloudy so call it a night and bring the stuff in. Of course, five mins later it clears. So I wait to see if it remains clear, and it does. So I get all the gear out again and set up again. Two subs in, it clouds over (again). I wait an hour or so to see if the cloud has set in for the night and it appears it has. So I take it all in for the second time. As soon as I have done so and just going in the house, it clears. Ahhhh, I say to myself, it'll cloud over again soon. But it didn't and it was clear for another ten hours.
^^^^^We have all been there. Equipment hokey-cokey, in-out-in-out.