[SQM] maps for Globe at Night

Jan Hollan jhollan at amper.ped.muni.cz
Wed Mar 3 00:28:12 UTC 2010

Connie and everybody, sorry for not working earlier. I made the needed 
maps at last.

> (But for the lower latitudes, 7pm does work.) It is a matter of people 
> knowing when it is dark enough to observe, which may not always be 
> possible.

7 pm legal time is a beginning of nautical night at equator, at its 
standard meridian (Sun lags 10 min those days). So it would work just for 
extremely polluted sites. If there is no change within the next hour, 
artificial luminance clearly dominates.

60 N needs 20:30 to be safely within astronomical night.

> Your maps would be a great addition. I am not sure how I can convince my 
> boss a couple days in advance that I should spend time along with the 
> webmaster to put these on-line now.  Is there a way you can quickly 
> provide us with information on which to display (each with an 
> explanatory caption) in a fashion that is easy for the general public to 
> understand?

I attempted to make printable pdfs for all the latitudes. They 
could/should be linked to from the Globe at Night site, in addition to the 
old white-on-black bitmaps. Perhaps, saying "printable version...". All 
are available at
All are computed for zenith extinction of 0.25 mag. Perhaps an information 
that < 5.5 mag means 5 mag should be added...

(50 N and 60 N are cylidric, another cones, all equidistant, 
undistorted parallels perhaps optimal).

hope it makes its way to this year's campaign...

best, jenik

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