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Old October 10th 04, 07:49 PM
John Ladasky
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"George Dishman" wrote in message ...
"Eugene Shubert" wrote in
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"Mr. 4X" wrote in message

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What is the darkest hour of the night?

That depends on a lot of things. There is almost no direct sunlight 2-3
hours after sunset,


Isn't there a measurable amount of sunlight that's scattered by the
atmosphere, reaching further into the night than a mere 2-3 hours of
earth rotation?


Zodiacal light.


I thought that the zodiacal light was scattered off of Solar System
dust in the plane of the ecliptic, rather than Earth's atmosphere?

When a sizable part of the earth's surface and atmosphere is heated up
during the day, doesn't a measurable fraction of that heated material
reradiate energy in the visible spectrum?

To keep the calculations simple, let's ignore artificial lighting but
factor in the reflected light of the Moon if you know how to do that.


It will be darkest at local midnight in midwinter
when the Moon is new and Venus is below the horizon.
I wonder how often that combination occurs (if ever).


How can Venus *not* be below the horizon at local midnight? Venus
reaches a maximum elongation of about 48 degrees relative to the Sun.
If I've done the math correctly, Venus should always be below the
horizon by 3 hours and 12 minutes after sunset.

George


--
Rainforest laid low.
"Wake up and smell the ozone,"
Says man with chainsaw.
John J. Ladasky Jr., Ph.D.