Author Topic: New Light Pollution Atlas w/o Snow Cover  (Read 617 times)

gladinises

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Re: New Light Pollution Atlas w/o Snow Cover
« Reply #30 on: February 08, 2018, 08:57:28 PM »
Really thanks for your work. I was in green, now I am in blue and gray is 15 minutes away. Black is 30-40 minutes. You made my day.Dark skies.mm

Todd Vann

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Re: New Light Pollution Atlas w/o Snow Cover
« Reply #31 on: February 09, 2018, 10:19:28 AM »
The issue of sky brightness' lack of correlation with the satellite light maps is well-known.In the southwest, my neck of the woods, light pollution seems to relate extremely well to humidity in the lower atmosphere.  We have the greatest amount of dust in the lower atmosphere when it is dry and windy, yet the brightest skies are when the humidity near the ground creeps up.So a site that is in, for instance, a red zone, might get a reading of 16.8 when the humidity is high, and a reading of 17.5 when the humidity is low.This idea corresponds well to what I see at my home--Polaris is an averted vision object when the sky is very hazy and humidity is 80% or more, while magnitude 4 stars are easily visible when the humidity is near zero.It's possible it is not solely humidity but the interaction between airborne water vapor and smog or dust.  But I have taken measurements at my home for over 5 years and the transparency of the sky varies right along with the humidity.  Air SHOULD be just as transparent with water vapor in it, but it's not.That factor seems to make any sort of absolute light pollution map unlikely unless you have annual averages for each site correlated to a color map.