With the term light
pollution one intends the disturbing effects of the man-made lights spread
out over the entire sky.
The total contribution of
artificial nighttime lighting, coming from nearby cities for example,
makes the sky background brighter than the other sites located far from
the big urban agglomerates. Such lighting has produced a veil over all of
our cities and is removing our view of the stars and the Milky Way.
The map on the right shows
the effects of the artificial lights produced in the city of Catania (bright
spot located at about 180 in azimuth) as observed at the stellar station
of the Catania Astrophysical Observatory. Anyway, Catania is the most
important source of light pollution but, unfortunately, not the only.
Besides, there are too many little town close to Catania, whose
contribution to artificial sky brightness is not negligible.
This map is part of my PhD
thesis and has been realized by photometric measurements in the standard
UBV system. For detail see the
paper "Measurements of the night sky
brightness at the Catania Astrophysical Observatory" written by
Catanzaro and F. A. Catalano and published in
"Measuring and Modeling Light Pollution", ed. P. Cinzano, Mem.
Soc. Astron. It., Vol. 71 , N.1, p. 211.