Omega Suns & Road Mirages ~ At upper right, Attila Kovács imaged a low sun above a hot road surface. The sun is miraged by the layer of heated air into a replica of an 'omega' or 'Etruscan Vase' sunset. At left Attila pictures an 'omega' miraged road sign. Lower left - A more typical omega sunset pictured over the sea from Maryland by Claudia Hinz.

Attila's images neatly demonstrate that omega sunset mirages are the result of a layer of warm air beneath cooler. For the upper right image - "The air temperature was 30°C and I measured the road surface being between 50-52°C - a difference of 20-22°C between the lower hot and the upper layer."

©Attila Kovács, shown with permission.
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The setting sun nears the horizon (or hot road!) and a second upside down sun segment rises up to meet it.

Rays from sun (or a nearby object) have to cross before reaching the eye if they are to form an inverted image.

At right a hot air layer close to the ground is causing a mirage. Ray 'a' leaving the arrow top passes through upper cool air with hardly any deflection. Ray 'c' from the same point is strongly deflected and reaches the eye after being refracted by the density gradients at the cool/hot air junction. To the easily deceived eye the upward going ray appears to come from an object beneath the ground.

The two rays, 'b' and 'c', cross and form a mirror image.

But usually mirages are as through a distorting mirror. Notice how the hot road mirage image of the sun is highly flattened.

In a later OPOD we shall see why there is vertical flattening and stretching, why inverted images always adjoin erect ones and more...

Terrestrial and astronomical inferior mirages: The essence - ray crossing remains the same. However, we have to imagine that the sun at infinity. Rays from its upper and lower limb strike the temperature gradients inclined 0.5° differently