The journal [...] says that the full moons should be aligned with stars (wich are always placed inside that top circle) and the darkness should stay below (dark moons go to the bottom circle).
After a little research, I realized I hadn't noticed the small stars placed in the top circle. I'd seen them on the mural and thought they were supposed to match up with the beam of light, but that's my mistake : they match the identical stars in the top circle on the temple floor. That's the clue that unambiguously orients the mural in the room; I missed it plain and simple.
So I guess in the end the beam of light is kind of a red herring. It's the most visible element in the room but isn't actually helpful in solving the puzzle. Well played, Larian. Ya got me.
