Calculated sky brightness in the evening, without clouds

The sky brightness is a measure of how dark it is at night. It concerns the luminance (blood strength per unit area) in the point in the sky when you look straight up (so-called Zenit). The luminance varies greatly in one location. In this map you can see the calculated sky brightness, expressed in milicandela per m² for the situation: [1] In the evening without clouds. [2] In the night without clouds. [3] in the evening with clouds. [4] in the night with clouds. N.B. Only Dutch sources are included in the calculation. There are no sources from abroad. Because of this, the calculated celestial brightness in the border region is probably an underestimation of the real celestial brightness.