Count the Stars to Save the Sky

For generations, amateur astronomers have measured the quality of their skies by the naked-eye limiting magnitude (NELM) — the faintest star that can be seen without optical aid. The relentless spread of light pollution has added a new urgency to this time-honored method. It's now possible to measure skyglow directly both from the ground and outer space, but NELM remains the only good way to compare current conditions against the past, to see how light pollution progresses over time.

More than 6,000 people across the globe participated in the Great World Wide Star Count of October 2007.
University Corporation for Atmospheric Reasearch
Besides, only dedicated stargazers are likely to invest in a specialized device to measure skyglow, like Unihedron's Sky Quality Meter. But with a little help, every man, woman, and child with normal vision can estimate the limiting magnitude. And the Internet makes it possible to gather and correlate the data on a scale that was never possible before.

That's the idea behind the Great World Wide Star Count. Inspired largely by Fred Schaaf's article "Count Light Pollution Out" in the April 2007 Sky & Telescope, the 2007 World Wide Star Count collected 6,600 observations from participants on all seven continents — yes, even Antarctica.

This year's count runs during the two weeks of moonless evenings from October 20th to November 3rd. See the home page for details about how you can participate.

So why not pitch in? It will take just five or ten minutes of your time, and it's lots of fun. It's also a great opportunity to get your family and neighbors to look up at the sky. There's nothing like asking people to look for stars to make it painfully clear just how onerous poorly designed lighting can be.

2 thoughts on “Count the Stars to Save the Sky

All comments must follow the Sky & Telescope Terms of Use and will be moderated prior to posting. Please be civil in your comments. Sky & Telescope reserves the right to use the comments we receive, in whole or in part, and to use the commenter’s username, in any medium. See also the Terms of Use and Privacy Policy.


This site uses Akismet to reduce spam. Learn how your comment data is processed.