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Q&A: Measuring the Darkness of Your Night Sky

8 Jun 2015, 07:01 UTC
Q&A: Measuring the Darkness of Your Night Sky
(200 words excerpt, click title or image to see full post)

Question: I live in a rural area north of Phoenix, Arizona. And even with a mountain between me and the city I still get a lot of sky glow that interferes with my hobby, astronomy. I’m aware of the fact that cities keep growing, and that brings more light pollution. But I’m wondering if there’s some way I can measure the degree of light pollution over time. I don’t expect it’ll ever decrease, but it would be good to know how fast it’s increasing. Any suggestions? — SS, New River, AZ
Answer: Yes, there are at least three reliable methods to assess the degree of light pollution in a given area. But before I explain, take a look at the image above. It’s a composite of night views over the entire planet. Click on it to see an even larger image. If you live in a major city, you can probably find the spot of light that corresponds to it.
And therein lies the problem of light pollution. If those lights can be seen from space, that means the light is traveling upwards through the atmosphere. The air scatters the light in all directions and reduces the contrast between ...

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