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“There is a theory which states that if ever for any reason anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”
- Douglas Adams

Milky Way (Dave Dockery)

  
Light Pollution Facts

Light Pollution Solutions

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Examples of Bad Lighting

Unfortunately this is the type of lighting most seen around Las Cruces. Look over all of the pictures. See what they have in common? They all have a glass enclosure or lens. The only purpose in most of these is to diffuse the light, and protect the bulb. It does nothing to control where the light goes.

Bad Lighting (image by S. Henderson) Bad Lighting (image by S. Henderson)
Bad Lighting (image by S. Henderson)
Bad Lighting (image by S. Henderson)

Look at the two pictures to the right. They look like Full Cut Off fixtures don’t they? (see “The Good” page for an explanation of “Full Cut Off”) Look closely. The lens hangs down below the bottom of the fixture. Commonly called a “Sag Lens” because it sags below the bottom of the fixture. These ARE NOT Full Cut Off fixtures. They allow light to be emitted at a horizontal plane

Bad Lighting (image by S. Henderson)

Bad Lighting (image by S. Henderson)


Examples of Good Lighting

Notice the lighting below. Do you see anything in common with the different styles of fixtures? They are all “Full Cut Off” (aka “Dark Sky Friendly” or “Neighbor Friendly”). It doesn’t matter if it’s mounted to a wall, or a pole. Look at the bottoms of all the different fixtures. They all have flat glass lenses. That is the sign of a “Full Cut Off” fixture. The light source (bulb) is up inside of the fixture. This design doesn’t allow any light to shine above horizontal, and in most cases well below.

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Good Lighting (image by S. Henderson) Good Lighting (image by S. Henderson) Good Lighting (image by S. Henderson) Good Lighting (image by S. Henderson)
Good Lighting (image by S. Henderson)
Good Lighting (image by S. Henderson)

 

Notice the added shielding on the fixture on the right to further control light trespass, excellent!

Good Lighting (image by S. Henderson)

Good Lighting (image by S. Henderson)

Retrofitting Existing Lights

On the left is an example of an older “Cobra Head” “Sag Lens” streetlight. The picture on the right shows how these light polluters can be retrofitted with shields to become a Full Cut Off fixture. Shielding may be used to inexpensively retrofit many types of lights. A modern "Cobra Head" is shown on the far right.

Good Lighting (image by S. Henderson) Good Lighting (image by S. Henderson)