[SQM] a "ground albedo influence" night

Jan Hollan jhollan at amper.ped.muni.cz
Sun Dec 20 16:16:57 UTC 2009

Dear friends,

just a reminder: a bright night with almost all landscape covered with 
cold white snow (here in Brno, just very concentrated salt water could 
thaw it recently) is an ideal opportunity to get the important number:

            what amount of sky luminance is due
          to the light disperesed from the ground

This differs within towns and far from them, of course. But even within 
towns, the amount of sky luminance due to direct emissions from 
luminaires is, fwith no snow, larger, unless the lighting is fully 

Comparison of snowless and snow-rich winter measurements (with the same 
zenith extinction, if possible, or under a known one at least) is our main 
tool in this respect. It can overweight any (wrong) models offered by 

Fabio and I have written about it several times already, but there are not 
many data like that yet. We had a week with snow here in Brno already, but 
this night is the first clear-sky one.

So, don't miss the opportunity, if it will appear -- tonight or any other 
night this winter.


PS. sorry for not responding to darksky issues at all, I'm overwhelmed by 
working on the climate enlightment these months.

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