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Light pollution

I am observing from Leiden, Netherlands. You can see where this city of 120,000 inhabitants is located on the light pollution map below. It is exactly between the two large cities of Rotterdam (South) and Amsterdam (North) that appear as two local maxima in the color code.

The map is a copy of a larger one taken from http://www.lightpollution.it/dmsp/starvis.html. The various colors represent the naked eye star visibility in V magnitude :

6.0 black 5.75-6.0 grey 5.5-5.75 blue 5.25-5.5 light blue 5.0-5.25 azure 4.75-5.0 yellow 4.5-4.75 golden yellow 4.25-4.5 orange 4.0-4.25 dark orange 3.75-4.0 red 3.75 violet