How to detect if the player is looking at the sky

So for a long time, I've been trying to figure out how to do a procedure that detects if the player is looking at a full moon. I think I figured out how to detect if there is a full moon out, by doing "get moon phase factor = 0", but I'm not sure how to detect if the player is looking straight up. There's like things for detecting the pitch of the player's head, but idk what angles to use, or even if it would actually work. If someone could help that would be great 😃👍🏼