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GLOBE at NightGLOBE at Night, now in its 6th year, encourages astronomers and citizen-scientists worldwide to record the brightness of the night sky to help create a global map of light pollution. During two weeks of moonless evenings, observers compare the appearance of a constellation (Orion in February/March and Leo or Crux in March/April) with the view depicted on seven charts showing progressively fainter stars. They then go online to report their date, time, location, and the number of the chart that best matches their view of the constellation. New this year: Observers with smart phones or tablets can submit their measurements from the field in real time!

What: GLOBE at Night: Less of Our Light for More Star Light

When: 8 p.m. to 10 p.m. local time, February 21 to March 6, 2011 (worldwide)
             8 p.m. to 10 p.m. local time, March 22 to April 4, 2011 (N. Hemisphere)
             8 p.m. to 10 p.m. local time, March 24 to April 6, 2011 (S. Hemisphere)

Where: Everywhere!

Who: Everyone!

How: See for details.

Why: Half the world’s population is now living in cities. Many urban dwellers have never experienced the wonder of a pristinely dark sky and maybe never will. This loss, caused by light pollution, is a is a serious and growing global concern on many fronts: safety, energy use, cost, health, effects on wildlife, and a diminished view of the stars.

Participation in the international star-watching campaign GLOBE at Night helps to address the light-pollution issue locally as well as globally. This year, two campaigns are being offered. For the first, from February 21 through March 6, 2011, everyone all over the world is invited to record the brightness of the night sky. The second campaign runs from March 22 through April 4 in the Northern Hemisphere and from March 24 through April 6 in the Southern Hemisphere.

The campaign is easy and fun to do. You start by matching the appearance of the constellation Orion in the first campaign (and Leo or Crux in the second campaign) with simple star maps of progressively fainter stars. Then you submit your measurements, including the date, time, and location of your comparison. After all the campaign’s observations are submitted, the project’s organizers release a map of light-pollution levels worldwide. Over the last five annual two-week campaigns, volunteers from more than 100 nations contributed 52,000 measurements. Last year's campaign accounts for one-third of those.

For the 2011 campaigns, observers with smart phones or tablets can submit their measurements in real time. To do this, you can use GLOBE at Night's new Web application. With smart phones and tablets, the location, date, and time are put in automatically. Otherwise, there are user-friendly tools on the GLOBE at Night report page to find your latitude and longitude.

To learn the five easy steps to participate in the GLOBE at Night program, see the GLOBE at Night website. You can listen to a 10-minute audio podcast on light pollution and GLOBE at Night. Or download a 45-minute PowerPoint presentation and accompanying audio narration. GLOBE at Night is also on Facebook and Twitter. To help children explore what light pollution is, what its effects on wildlife are, and how to prepare for participating in one of the GLOBE at Night campaigns, see the Dark Skies Rangers activities.

Monitoring our nighttime environment will allow us as astronomers or citizen-scientists to identify and preserve dark-sky oases in cities and to locate areas where light pollution is increasing. All it takes is a few minutes during one of the 2011 campaigns to measure night-sky brightness and contribute those observations online. Help us exceed the 17,800 observations contributed last year. Your measurements will make a world of difference!