Anti-twilight Colors and Belt of Venus

January 30, 2023

Evolution of Twilight - The Four Bands LD (1)

Antitiwilight Colors And Belt Of Venus LD caption

Photographer: Dario Giannobile 
Summary Author: Dario Giannobile 

Shown above are two different portrayals of the anti-twilight sky and the Belt of Venus as observed near Syracuse, Sicily, Italy. The image at top was taken on January 4, 2023. In essence, twilight is sunlight scattered by the atmosphere that's still visible when the Sun is below the horizon. Four main visual components of the anti-dusk have been identified:

• the blue “upper sky” (US) extending downwards from the observer's zenith

• the reddish “Cintura di Venere” (BV)

• the "blue band" (BB), located below the Belt of Venus and is part of the shadow of the Earth

• the “horizon band” (HB) -- a band of sky between the blue band and the horizon, that although located further into the Earth's shadow, is slightly brighter than the blue band.

Color variations in the Anti-twilight sky result from different physical phenomena such as Rayleigh scattering, molecular absorption, aerosol scattering, multiple scattering and refraction.

For the bottom image, I used 20 separate shots, taken 2 1/2 minutes apart. To better highlight the color transition, each image was created with the same exposure by setting the camera to aperture priority mode. Furthermore, a single white balance was used to highlight the relative variation of the colors of the various portions of the sky at different instants. Although it's not possible to determine with scientific certainty the absolute color captured in each shot, maintaining a constant white balance allows relative color transitions to be highlighted. Distortion in height was employed to show in a single view the different bands that form during sunset. Photos composing this image were taken on November 18, 2022.


Syracuse, Sicily, Italy Coordinates: 37.0755, 15.2866

Related Links:

Mount Etna, Alpenglow and Belt of Venus

Dario’s Website

Belt of Venus from Isola d'elba, Italy