Light Pollution is the term used to describe the light wasted every year by trying to escape into space. While some of this light does escape into space, some of it is also reflected back down by the atmosphere, causing our nights to seem brighter than they should be. Because of this, it is harder for stargazers, as well as astronomers, to view the night sky with great detail. This is because the light reflected down from our atmosphere makes the sky seem brighter, which makes it harder to see stars that aren't that bright. The animation on this page shows just how drastically light pollution can affect our visibility of stars. While to some people that means that we can't see the beauty of the sky, it is an even bigger problem to astronomers who want to take data on the night sky. You'll notice that on the bottom of every picture is the site name, and a number next to it. This number is using the units Magnitudes per Arcsecond squared (mag/arcsec2). 22 mag/arcsec2 is a completely clear sky with no light pollution, and as the number gets lower, so does visibility of stars.
Click here for more information on the different sites used.
This is a picture of NGC 6946, a spiral galaxy that is about 10 million light years away. This picture was taken by Professor Andy Layden on August 28, 2002 at Kit Peak Observatory. It was taken with the WIYN 0.9m telescope and S2KB CCD, and was a 200 second exposure though a V filter. The picture was taken when the galaxy was 2.5 hours west of the meridian and when the moon was a waning gibbous (72% illuminated). On that night there was cirrus clouds present in the East, but clear in the west where NGC 6946 is.
This movie is showing 0.5 mag/arcsec2 increments.
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