Shades of Night

As seen on Astronomy Picture Of the Day. A photo composite of multiple exposures. From the photographer: “All the characteristics that can develop during anti-twilight. The image was created by continuously shooting the sunset and setting the camera to maintain constant exposure (AV Priority). 20 shots were chosen to show the evolution of colors in the east during sunset. From the left it is possible to observe in order: the shadow of the earth, the belt of Venus and the illuminated sky during the beginning of twilight.

Moving to the right we observe the belt of Venus becoming increasingly pink and the Earth’s shadow detaching from the horizon. At this moment the pale blue horizon band appears. Up to this moment the characteristics highlighted are the best known ones. During this sunset characterized by a particular transparency over the entire obstacle-free horizon, a second dark red band appeared. In the book “Light and colors in the outdoor”, Marcel Minnaert reports that a band of meat-red color appears at the terminal moment of twilight. According to the author it is caused by the illumination of diffused violet light rather than by the Sun itself.

Finally, just above the horizon on the far right you can see the formation of a second band of more intense color. This characteristic seems to coincide with what the author himself reports, namely the formation of a second shadow of the Earth, shortly before the disappearance of the violet light. Apart from Marcel Minnaert’s reporting and interpretation, no other references can be found on this phenomenology which should be analysed more thoroughly. However, what I was able to verify is that the sky was free of dust and we were in the presence of very low aerosols as can be verified from the data from the Copernicus satellite. Furthermore, the contemporaneity between the formation of these last two bands and the presence in the west of the terminal light of twilight with a color tending towards orange/purple remains confirmed.”

Technical Details:
Canon 6d, 50mm, f/5.6, iso 100
Actually it is a composition of 20 images of the same location captured in AV priority to keep the exposure as constant as possible. Each single vertical stripe is a moment in the anti – twilight.
All images has been developed with the same white balance in order to show the relative color variation over the time.