Atmosphere act as a Lens

Experts in optics and weather have concluded that "the atmosphere really does act like a lens." What type of lens? A convex lens. What does a convex lens do? It magnifies.

This experiment show how cities or boats can be obscured at a distance due to magnification and refraction of the light over a large body of water.

Obviously, the more moisture that is in the air, the larger the potential magnification would be. Likewise, when there is less moisture in the atmosphere, you would observe the less obscuration, Sun and Moon get smaller as they set.