The public's "right to starlight" is steadily being eroded by urban illumination that is the bane of astronomers everywhere, the International Astronomical Union said on Friday.

The public's "right to starlight" is steadily being eroded by urban illumination that is the bane of astronomers everywhere, the International Astronomical Union said on Friday.

The body, which wrapped up an 11-day general assembly in Rio de Janeiro that attracted galaxy-gazers from around the world, argued that authorities should use more unobtrusive lighting in cities and towns.

Such moves would not only free up the night skies to make for easier viewing but also promote environmental protection, energy savings and tourism, it said in a resolution.

"The progressive degradation of the night sky should be regarded as a fundamental loss," the union said.

It asserted that being able to see the stars "should be considered a fundamental socio-cultural and environmental right."

One Brazilian , Augusto Daminelli, told the Estado de Sao Paulo newspaper that in Rio, "it should be possible to see up to 5,000 stars with the naked eye -- but because of we can only see 150."

He noted that nearly a third of electric lighting is directed to the heavens, and thus wasted.

Possible solutions include putting aluminum covers on street lighting to direct the downwards, and using weaker, more energy-efficient lamps, he said.

"More than two billion people in the world are unable to see the . For us, the sky is a heritage site for mankind," he said.

(c) 2009 AFP