Ghost of a flea

Milky Way over a Florida Hammock

"Well, the milky way does look like a huge, sprawling light cloud under a clear dark sky, the stars blend together. You just can't see the purple--and it's the same with almost every deep sky object. With a few notable exceptions, everything looks black and white in the eyepiece of a telescope.

"The two kinds of photoreceptors in the eye are rods and cones. Cones are "color" vision, triggering on red, green, and blue wavelengths, and we have about 6 million. Rods are nightvision, and we have 120 million...so our nightvision is far more sensitive, but it lacks all color perception, triggering as luminosity only between the blue and green wavelengths. When you see color at night, you are actually seeing your color vision and nightvision at the same time. (They operate independently and combine in your brain.)
I
"nterestingly, this is why astronomers use red light. Bright light causes your rods to "turn off", but your rods can't see red, so using red light doesn't switch off your nightvision."

Posted by Ghost of a flea at May 26, 2013 10:17 AM