Published in the Forum on 12/14/03 in the Fayetteville Observer

Consider Light Pollution

By John Mattox

Professor of Astronomy and Physics, FSU

If not carefully designed to avoid unnecessary light pollution, the kaleidoscope tower would compromise the ability of Fayetteville residents and visitors to appreciate the natural beauty of the night sky.

We are seeing less and less of the natural wonders of the heavens because of a growing problem known as light pollution. It results from outdoor lighting illuminating the air above. Astronomers track the increase of outdoor lighting with the downward looking DMSP satellites. The figure below shows the DMSP image for the Fayetteville Region.

Figure caption - U.S. Air Force Defense Meteorological Satellite Program (DMSP) image made from space. The brightest areas (e.g., Charlotte at the left) are white; followed by red, orange, yellow, green, blue, and gray. Black represents a region with a sky of natural brightness. Fayetteville is the red area at the center of this image with Raleigh-Durham to the north and Wilmington to the SE. Even modest sized towns are apparent in this image (like Elizabethtown, between Fayetteville and Wilmington, on the western edge of the relatively dark Bladen Lakes State Forest).

This image shows that the lights of Fayetteville are currently visible from space, confirming the fact that Fayetteville already has substantial light pollution. Whereas the Milky Way Galaxy used to be a common sight, it is no longer apparent without traveling a substantial distance away from the city.

The web site of the International Dark-Sky Association (IDA – see www.darksky.org) provides information about the extent of light pollution, and how outdoor lighting can be designed to reduce light pollution while still providing sufficient light for safety and commerce. The most serious problem with badly designed outdoor lighting is glare. It occurs when light shines directly in our eyes.

Through careful design, I believe the kaleidoscope tower could be an attractive addition to the Fayetteville landscape that would not add unduly to light pollution. The brightness should be limited to not exceed the level required to be easily visible. The IDA has found that most outdoor lighting needs can be met with a brightness much lower than normally used - the human eye is a very efficient detector of low levels of light (e.g., the Milky Way Galaxy) if inappropriate bright lights and glare are not present.

I suggest that no beacon be placed atop the tower. Even if pointed upward (and thus not creating glare), it would increase the brightness of our sky, diminishing opportunities for residents and visitors to appreciate astronomical wonders, either with a telescope, or through casual observation. Also, the utility of the Observatory at FSU (but not the Planetarium) would be compromised. In addition, a beacon would cause confusion of migratory birds, causing some deaths through collision.