The Elusive Antitwilight Bands

February 09, 2024

The elusive bands of anti-twilight Caption LD

Photographer: Dario Giannobile 
Summary Author: Dario Giannobile  

This photo shows the three main bands that can be identified during antitwilight (be it before sunrise or after sunset). It was taken in the Sicilian countryside of Gela (Italy) as the Sun was setting on November 16, 2023. 

Belt of Venus (BV) - The BV begins to appear when the Sun first grazes the horizon and then sinks approximately -2 degrees below the horizon. It appears pinkish because of the greater path-length of sunlight when the Sun is on the horizon. When the sun lowers between -3 degrees and -6 degrees, the belt begins to lose the red component and the blue tends to prevail. At this stage its contours begin to fade and become increasingly indistinguishable.

Blue Band (BB) - As the Sun sinks further below the horizon, the rising Earth’s shadow is cast on the atmosphere. Its bluish hue is more noticeable after the Sun is about -4-5 degrees below the horizon and completely replaces the BV when it reaches -8 degrees.

Horizon Band (HB) - Of all the bands, the horizon band is certainly the most elusive to observe and requires very specific conditions of atmospheric transparency. This band is mainly due to the observation line near the horizon. Being opaque, the atmosphere amplifies dispersion of light by acting on all colors with more or less equal efficiency. For this reason, it appears whiteish.


Photo Details: Canon 6d camera; Sigma 105 mm lens; f/11; 105 mm focal length (13 degrees x 19.5 degrees); .0,8 seconds exposure; ISO 100.

Gela, Sicily, Italy Coordinates: 37.0742, 14.2404

Related Links:

Antitwilight Colors and Belt of Venus

Dario’s Website