The night sky was what could be seen of the sky during the nighttime hours.
The Beacon of Kahless was part of a prophecy that said all Klingons must come to the the beacon when it shines in the night sky. (DIS: "The Vulcan Hello")
In 2268, James T. Kirk asked Shahna if she ever looked at the night sky. When she said she had, he showed her the stars, saying there were planets around them on which people like them lived. (TOS: "The Gamesters of Triskelion")