The longer awake the better. The best stargazing always seems to be in the coldest weather. There were always those apocryphal stories of people getting their eye ridge frozen to the eyepiece. And if you’re so tired that you fall asleep regardless of the noise, then so be it. I remember lying outside on the Indiana dunes with the rest of the Adler Planetarium staff as we watched for meteors. Magical.
All tents are essentially clear if you take off the fly