HOW DARK IS MY SKY?
NOW everyone, astronomers, nonastronomers and children, too, can measure sky darkness with my easy-to-use dark sky scales:
5-star scale like movie reviewers use.
5-grade scale like teachers use.
All you’ll need is a clear, moonless night, a place where most of the sky is visible overhead and 3 simple steps:
- Go outside when the sky is dark (90 minutes after sunset or before sunrise).
- Look up and scan the sky for approximately 15 seconds.
- Estimate how many stars you see based on the categories below.
5-star sky (Grade A): Zillions of stars and the Milky Way visible from horizon to horizon in a pristine dark night sky, far from city lights! The following sky maps will show you what each season’s sky might look like:
4-star sky (Grade B): Thousands of stars and a hint of the Milky Way.
3-star sky (Grade C): Hundreds of stars and Milky Way lost in glow of light.
2-star sky (Grade D): Dozens of stars are visible. No Milky Way visible.
1-star sky (Grade F): Few stars (fewer than 20) are visible.
Use plus and minus (for grades) and "tenths" of a star to make your dark sky measurement more accurate. . .see below.
In 1995 the night sky over my backyard averaged 3.5 stars (B-). Tonight it will average 4 stars (B). I live in the center of Ames, Iowa, population 50,700.
What’s your sky darkness rating? Please send it to me at: troegerj@raccoon.com
We cannot hope to restore a 5-star sky (A) over all of America, but we can work to reclaim a 4-star sky (B) and preserve 5-star skies (A) where they now exist.
Initiate a DARK SKY REVOLUTION in your town!
© Jack Troeger, Dark Sky Initiative. troegerj@raccoon.com
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