Omega Sunset Over Key West, Florida

July 14, 2021

Birth of the Omega

Photographer: Robert Pickard

Summary Author: Robert Pickard & Cadan Cummings

The composite photo of Sun images above details the different stages of a sunset as observed from Key West, Florida. Due to the atmospheric refraction of sunlight when the Sun is low in the sky, the solar disk appears as a beautiful yellow-orange gradient and in the shape of the Greek letter omega (Ω) or Etruscan Vase. The phenomenon results from an inferior mirage caused by a layer of dense, cool air on top of less dense, warmer air. This optical event occurs when the ocean temperature is warmer than the air temperature and heats a layer of air immediately above the water surface. As sunlight approaches the water surface, the light is refracted upwards and makes the mirage appear below an object’s true position. This culminates in the fifth and sixth composite images when the Sun and its mirage optically join into the familiar omega shape. A related solar phenomenon is occasionally noticeable at sunset when a green flash is visible above the upper rim of the solar disk. This rare event was also visible during my three day trip as I saw multiple "flashes" occurring at the top of the setting Sun.

Make sure to always view the Sun safely using proper filters or techniques.  Photos were taken on May 5, 2021 near the famed Mallory Square in Key West, where the island population and tourists have a daily sunset celebration.

Photo data: Camera- Nikon D3200 (with T-ring adapter), Exposure- 1/500s, ISO-100, Telescope- Orion ShortTube 80 refractor with Celestron Omni CG4 mount (untracked)

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