  Europe and a number of countries in the world are investing significant
amounts of public money to operate and maintain large, ground-based
astronomical facilities. Even larger projects are under development to observe
the faintest and most remote astrophysical sources in the universe. As of
today, on the planet there are very few sites that satisfy all the demanding
criteria for such sensitive and expensive equipment, including a low level of
light pollution. Because of the uncontrolled growth of incorrect illumination,
even these protected and usually remote sites are at risk. Although the reasons
for intelligent lighting reside in energy saving and environmental effects, the
impact on scientific research cannot be neglected or underestimated, because of
its high cultural value for the progress of the whole mankind. After setting
the stage, in this paper I review the effects of improper lighting on
professional optical and near-UV astronomical data, and discuss the possible
solutions to both preserve the night sky natural darkness and produce an
efficient and cost-effective illumination.
