The artificial
sky brightness in each site at a given position on the sky is obtained by integration
of the contributions produced by every surface area in the surroundings of the
site, based on detailed models the propagation in the atmosphere of the upward
light flux emitted by the area
and measured by the Operational
Linescan System
of DMSP
satellites.
Where in Europe can we still see the stars without being hindered by ambient light? Not in many places. We would have to go to the northern areas of the scandinavian countries, the far north of Scotland, or, to Spain. Yes, there are still a few places in Spain where night sky polution by light is still very limited.
Compared to the rest of Europe, Spain still has relatively large areas without ambient light polution. Here is a more detailed night sky polution map of Spain and Las Villuercas.