Earthlight (astronomy)

[3] When the Earth is at maximum phase, the total radiance at the lunar surface is approximately 0.15 W m−2 from Earthlight.

On these nights, the entire lunar disk is both directly and indirectly sunlit, and is thus unevenly bright enough to see.

The term earthlight would also be suitable for an observer on the Moon seeing Earth during the lunar night, or for an astronaut inside a spacecraft looking out the window.

High contrast photography is also able to reveal the night side of the moon illuminated by Earthlight during a solar eclipse.

The phenomenon was sketched[8] and remarked upon in the 16th century by Leonardo da Vinci, who thought that the illumination came from reflections from the Earth's oceans (we now know that clouds account for much more reflected intensity than the oceans).

The night side of the moon, illuminated by earthshine, becomes visible next to the narrow crescent (11 percent, age of the moon = 3.3 days) with ash-grey moonlight. Image taken 20° over the western evening sky shortly after the equinox in spring with a particularly steep ecliptic as seen from Berlin. On the left, the star Omicron Arietis (37 Ari, 6,2 m ) in the constellation Aries .
During the crescent phase , the darker side of the Moon reflects indirect sunlight , reflected from Earth, while the other side reflects direct sunlight.
An 80 mm shot of a crescent Moon with a 10-second exposure, revealing earthshine. The green ghost image was caused by a UV filter on the lens.