Earth's shadow

[2] Earth's shadow cast onto the atmosphere can be viewed during the "civil" stage of twilight, assuming the sky is clear and the horizon is relatively unobstructed.

No defined line divides the Earth's shadow and the Belt of Venus; one colored band blends into the other in the sky.

This is because the light rays are penetrating an especially thick layer of the atmosphere, which works as a filter, scattering all but the longer (redder) wavelengths.

From the observer's perspective, the red sunlight directly illuminates small particles in the lower atmosphere in the sky opposite of the Sun.

The lower the setting Sun descends, the less defined the boundary between Earth's shadow and the Belt of Venus appears.

Earth's shadow (blue) and the Belt of Venus (pink) at dawn , seen above the Pacific Ocean (blue-grey), looking west from Twin Peaks , San Francisco
Earth's shadow and the Belt of Venus at dusk , looking east from the Marin Headlands just north of San Francisco in October 2010.
(Note: A thin layer of greyish cloud partially obscures the horizon in this image.)
A full moon rising, as seen through the Belt of Venus. A very small part of the Earth's shadow (dark blue) is also visible in this image, but the horizon here is too high for more of the Earth's shadow to be seen.
A total lunar eclipse on May 15, 2022 , shows the reddish light falling on the Moon's surface.