Category talk:Moon illusions
Another, perhaps related illusion has to do with the angle at which the (other than full) moon appears tilted in the sky. The effect is most obvious when viewing a waxing quarter moon late in the afternoon. The moon is visible in the southeast and appears to be lit from a sourse at a higher altitude than itself, while the sun is still visible in the southwest at a much lower apparent altitude. The straight line dividing the dark and light halves of the moon should be perpendicular to a straight line connecting the moon and sun, but the appearance is not even close.