Mapping light pollution



Los Angeles

Scenes of city lights, like this one of San Francisco Bay, might be beautiful, but they're also a reminder of how light pollution can cloud our view of the stars.

Credit: Thomas Hawk

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As urban light pollution continues to cloud our view of the skies, a global survey aims to map its spread - with the help of amateur star gazers.

The Great World Wide Star Countis an international project which pools skyward observations taken by citizens around the world. The information helps scientists measure the extent to which city lights mask the visibility of stars.

The project, in its second year, is organised by the University Corporation for Atmospheric Research, (UCAR) a consortium of 70 universities and the US National Centre for Atmospheric Research.

In 2007, more than 6,600 observers on all seven continents took part. From the data, UCAR created maps of star visibility around the world.

"Last year's results showed a strong correlation between dense development, where there is a lot of light, and a lack of star visibility," Ward says.

"Without even being aware of it, many of us have lost the ability to see many stars at night." says Dennis Ward of UCAR's Office of Education and Outreach.

Participants in the northern hemisphere will look for the constellation Cygnus, while those in the southern hemisphere will turn their attention on Sagittarius.

By focussing on particular constellations, sciences can more accurately compare how star visibility differs around the world.

Participants can download forms from the website.

People encountering cloudy weather can record their observations of the clouds instead.

This year the survey runs from October 20 until November 3.