Smithsonian.com

The constellation Leo, as depicted on a constellation card c. 1825 (via wikimedia commons)

In my neighborhood, some of the street lamps aim their light directly down on the sidewalk and road. Others spew their illumination in a sphere of light, wasting it as it streams into the sky. All those poorly aimed lights add up to 17 billion kilowatt-hours of lost energy each year, costing us around $2 billion. And, of course, they drown out the awesomeness of the night sky.

The National Optical Astronomy Observatory in Tuscon has been documenting this light pollution each spring for the past six years, and they are set to start the next round of GLOBE at Night tomorrow here in the Northern hemisphere, where it runs through April 4 (the program is March 24 through April 6 in the Southern hemisphere this year). Here’s how you can participate:

1 ) Determine your latitude and longitude (write it down). Options include using GPS, Google Earth, the GLOBE at Night webapp.

2 ) Go outside about an hour after sunset and find the constellation Leo (if you’re in the Northern hemisphere) or Crux (Southern). The GLOBE at Night website can provide you with a constellation finder, or you can use your own method. (I’ve got the Planets app on my iPhone, for example.)

3 ) Match your sky to one of the magnitude charts. (You can print them out or access them from your favorite device outside.)

4 ) Use the webapp to report what you saw (or how little you were able to see).

“All it takes is a few minutes for a family to measure their night sky brightness by noting how many stars are missing from an easy-to-find constellation like Leo or Crux,” says project director Connie Walker. “This tells us how much light is directed upwards into the sky.” And it helps to document the patterns of light pollution.