Luminous Night

The initiated know this experience as the happy gate of blackness. .. which art the passage to this so glorious change It is the gate of Saturn. Apuleius describes his experience of Luminous Night with the mysterious words ... 

Scotopic vision sk9- to-pik vi-zhon. The vision mediated by rods alone at very low levels of luminance night vision. 

The appearance of the Lord, to one psychically unfolded to perceive IT, is as a luminous cloud, which fills the whole atmosphere like phosphorescent vapor. When God answered Moses from out the Burning Bush, he said his name was, "I AM THAT I AM," and Moses know what he meant, but not in a hundred million since that time has ever divined it. To make the matter plainer, it is stated that God went before the Israelites - "a pillar of fire by night, and a cloud by day," guiding them to the promised land. 

If the luminance of the sky near the horizon on a moonless clear night is 10-3 cd/m2, determine whether a star of magnitude 5 (0.1 cd/m2) would be seen. 

From a distance the camp looks like a solitary star in the cosmos it glows a sickly yellow its circles of light are no more than a luminous blur. Beyond the star, as far as the eye can see, is snow. It seems like the middle of the night. It is intensely cold. 

One of our joys was to go into our workroom at night, we then perceived on all sides the feebly luminous silhouettes of the bottles or capsules containing our products. It was really a lovely sight and always new to us. The glowing tubes looked like faint fairy lights. ... 

Rods are long and thin, and are more concentrated towards the periphery of the retina. As seen in Fig. 5.2, the maximum density is at 25° eccentricity, and decreases towards the outer edges of the retina. Rods only have one type of photopigment and can therefore only detect differences in luminance (i.e. these see only in monochrome). During night-time, when illumination is low and the iris wide open, the rods are used for vision (called scotopic vision). Peripheral vision in a dark environment is much better than foveal vision due to the low distribution-density of rods in the central part of the human eye. However, rods are about two-and-a-half times more sensitive than cones (Fig. 5.3, after data published by ) szechy and Stiles, 1982, p. 256). They do not contribute to photopic vision because of over-exposure when illumination is high (a process called bleaching). 

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