The Belt of Venus

The shadow of the Earth appears after sunset in the opposite horizon, as seen from atop the 3600m summit of Mount Gargash in Zagros Mountains of Iran. Note the red-pink glow or antitwilight band that extends the horizon. The glow is separated from the horizon by a dark layer which is the shadow of Earth in the atmosphere. The red-pink color above it is due to back scattering of reddened light from the setting Sun and is named the Belt of Venus. Not far from the town of Kashan, Mount Gargash has exceptional seeing and atmospheric transparency for astronomical observations and the climate and seeing at the peak are monitored as the main site for Iran National Observatory project. © Babak Tafreshi