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Bob Moler's Ephemeris Blog

01/25/2021 – Ephemeris – Why is the sky with the full moon gray?

25 Jan 2021, 05:01 UTC
01/25/2021 – Ephemeris – Why is the sky with the full moon gray?
(200 words excerpt, click title or image to see full post)

This is Bob Moler with Ephemeris for Monday, January 25th. Today the Sun will be up for 9 hours and 33 minutes, setting at 5:42, and it will rise tomorrow at 8:07. The Moon, 3 days before full, will set at 6:46 tomorrow morning.
The bright Moon is dominating the night sky now. Only the brighter stars are visible, with the fainter stars and constellations overwhelmed by the bright moonlit sky. It seems odd, but the gray clear moonlit sky that we see with our eyes is as blue as the daytime sky. Only it’s too dim to register on the cones in our retinas that can see color. The rods in our retinas can pick up light much better, especially if it is in the green part of the spectrum. We are pretty much insensitive to red at low light levels and color-blind as well. Star color is also subtle, and can be seen only in brighter stars. The colors run, from the hottest stars to the coolest: blue, white, yellow, orange and red. Also, there is a color shift at night. Stars with the same temperature as the Sun appear yellowish.
The event times given are for the ...

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