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The Question

(Submitted May 23, 1998)

I am doing a summer research project on the affects of light pollution on astrophotography. I was wondering if you could relay me any relevant information and hopefully methods for measuring light pollution. I have no way to measure different amounts of light pollution present at any given location and was wondering if it is even possible to measure.

The Answer

I've asked a colleague, George Gliba, who is a very experienced amateur astronomer, who provided me with the following answer.

You may also be interested in the International Dark Sky Association:

Best wishes,

Koji Mukai
for Ask an Astrophysicist

The best way to quantatively measure the amount of light pollution is by the determination of the limiting magnitude for stars visible from your area. It is known that, with ideal conditions, the average person should see stars as faint as 6.0 to 6.5 magnitude with the naked-eye. The International Meteor Organization's web site provides some guidelines for determining your limiting magnitude at the web site: (

This will provide you with different area of the sky maps, whose stars you can count to determine your limiting magnitude, and thus the amount of the light pollution in your night sky.

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