EPOD - a service of USRA

The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory
captions and links exemplifying features within the Earth system. The
community is invited to contribute digital imagery, short captions and
relevant links.


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 EPODs

Anti-twilight Colors and Belt of Venus Splendid Sundog over
Montreal, Canada The Fisherman and the Full Omega Moon Inferior
Mirage off the Coast of Sicily Crepuscular Rays Observed from
Italian Alps Halo Display Observed from Graubunden, Switzerland
More...

Atmospheric Effects Links

* Atmospheric Optics
* Optic Picture of Day: Gruppo Astrofili Galileo Galilei
* Color and Light in Nature
* The Colors of Twillight and Sunset
* Refraction Index
* Image Gallery: Atmospheric Effects
* What is a Rainbow?

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Space Research Association.

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