Moonlight

The moonlight, so the reflected moonlight, whether as a semblance of sunlight ( Moonlight ) or as a reflection of Earthshine ( earthshine ), is on average only one-millionth of the earth directly reach sunlight. Nevertheless, we the moon from the crescent appears blindingly bright, which is due to the contrast with the dark starry sky and the adaptation of the eye.

The intensity of moonlight depends primarily on three factors:

The latter two factors also affect the color of the moonlight.

The brightness of the full moon is in the astronomical brightness scale on average -12.5 likes, but varies with its distance from the Earth ( / - eight percent) by up to 17 per cent or 0.2 mag.

The brightness of the crescent is not based around 50 percent on the full moon, as one might think at first, but only about 11 percent, since only a fraction of the diffusely reflected light reaches the earth, which is approximately thrown back at right angles to the solar radiation, and the surface relief of the moon also casts shadows. With a very thin crescent, the brightness is only three to five percent of the full moon. In addition to the bright sunlit part of the moon surface erdzugewandten you can often also see the darker part, the not sun exposed, but the " whole earth " lit. This reflection of the Erdlichts, the " ashen moonlight ", makes up about 0.01 percent of the moonlight on a full moon.

Compared with the full moon, the sun is 300,000 times and 400,000 times brighter (-26 mag), the brightest planet Venus about 1500 times weaker (-4.4 mag) and the brightest star Sirius about 25,000 times weaker (-1.5 may ). The illuminance at the full moon and clear night is on Earth around 0.2 lux These differences appear to us considerably damped, because the sensations of the eye are perceived subjectively scaled approximately logarithmically according to their intensity differences ( Weber- Fechner law ).

A striking phenomenon can also be the Halo or yard of the moon. In cold autumn and winter nights high air layers can contain ice crystals, distract the parts of the moonlight side, so that a bright, sometimes slightly greenish pearly ring is formed. Depending on the position of this ice clouds can be only a few degrees of angle, as well as about 20 degrees, and ( rarely ) to about 40 degrees. The moonlight is thus only marginally weaker.