Sunrise/sunset phenomena

The blue hour is the period of twilight each morning and evening when the sun is a significant distance below the horizon and the residual, indirect sunlight takes on a predominantly blue hue. This effect is caused by the relative diffusability of short blue wavelengths of light versus the longer red wavelengths. During the blue "hour" (typically the period is about 40 minutes in length), red light passes straight into space while blue light is scattered in the atmosphere and therefore reaches the earth's surface. Because of the quality of the light, this period is treasured by artists. Photographers call it sweet light.




In photography, the golden hour (sometimes known as magic hour, especially in cinematography) is a period shortly after sunrise or before sunset during which daylight is redder and softer compared to when the Sun is higher in the sky.



The Belt of Venus or Venus's Girdle is an atmospheric phenomenon seen at sunrise and sunset. Shortly after sunset or shortly before sunrise, the observer is, or is very nearly, surrounded by a pinkish glow (or anti-twilight arch) that extends roughly 10°–20° above the horizon.

Often, the glow is separated from the horizon by a dark layer, the Earth's shadow or "dark segment." The arch's light pink color is due to backscattering of reddened light from the rising or setting Sun. A very similar effect can be seen during a total solar eclipse.




Green flashes and green rays are optical phenomena that sometimes occur right after sunset or right before sunrise. When the conditions are right, a green spot is visible above the upper rim of the disk of the sun. The green appearance usually lasts for no more than a second or two. Sometimes (rarely) the green flash can resemble a green ray shooting up from the sunset (or sunrise) point. Green flashes occur because the atmosphere can cause the light from the sun to separate out into different colors. Green flashes are a group of phenomena which stem from slightly different causes, and therefore some types of green flashes are more common than others.