I looked up for a while when I took the dog out and I was almost ready to grab a scope. There was a bit of twinkling on the bright stars which looked pretty normal for an average sky but when I watched dimmer stars I saw they were completely disappearing—so I went back inside.
I'm glad you guys got out though. I should'a went out anyway. I hope Friday brings good skies.
It sounds to me like you had a very slight case of condensation. You might not see it on the mirror (most likely the secondary) but if you can hit it with a blow dryer for half a minute you might see an immediate improvement.
That would be my first guess. Let us know if all returns to normal when you get out again.
Duane