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In a technique known as blue field entoptoscopy, the effect is used to estimate the blood flow in the retinal capillaries.The patient is alternatingly shown blue light and a computer generated picture of moving dots; by adjusting the speed and density of these dots, the patient tries to match the computer generated picture to the perceived entoptic dots.
The blue sky spectrum contains light at all visible wavelengths with a broad maximum around 450–485 nm, the wavelengths of the color blue. Diffuse sky radiation is solar radiation reaching the Earth's surface after having been scattered from the direct solar beam by molecules or particulates in the atmosphere.
Haidinger's brush, more commonly known as Haidinger's brushes is an image produced by the eye, an entoptic phenomenon, first described by Austrian physicist Wilhelm Karl von Haidinger in 1844. Haidinger saw it when he looked through various minerals that polarized light.
The photograph depicts a lush green rolling hill with cirrus clouds during a daytime sky, with mountains far in the background. [1] [2] It was taken by Charles O'Rear, a former National Geographic photographer and resident of St. Helena, California, in the Napa Valley region north of San Francisco, while on his way to visit his girlfriend in ...
The night sky and studies of it have a historical place in both ancient and modern cultures. In the past, for instance, farmers have used the state of the night sky as a calendar to determine when to plant crops. The ancient belief in astrology is generally based on the belief that relationships between heavenly bodies influence or convey ...
Skyglow (or sky glow) is the diffuse luminance of the night sky, apart from discrete light sources such as the Moon and visible individual stars. It is a commonly noticed aspect of light pollution . While usually referring to luminance arising from artificial lighting , skyglow may also involve any scattered light seen at night, including ...
Blue hour at the Old Cathedral of the Holy Name of Jesus, Bragança in Portugal. The blue hour (from French l'heure bleue; [1] [a] pronounced [lœʁ blø]) is the period of twilight (in the morning or evening, around the nautical stage) when the Sun is at a significant depth below the horizon. During this time, the remaining sunlight takes on a ...