By John Gilkison

Since Las Cruces is appointing an Ad Hoc comittee to draft a light pollution ordinance for the City Council, I wanted to try to explain what could be in it for the benefit of the average citizen. A very compelling case can be made for enacting outdoor lighting codes to control light pollution for other reasons than astronomy.

Most of the outdoor lighting practices and fixtures that impact people and astronomy were designed during a time when saving energy or minimizing enviromental impact was a minor concern. Often the primary design criteria was, put up a bright enough light and you will light an area.

Then lights kept getting more efficient, so as time went on, society could afford more and more of them. Today more outdoor lighting is in use per capita then anyone would have ever dreamed of 40 years ago.

Light emitted above the horizontal plane and being radiated away into space is waste light pure and simple. Since it benefits no one and and is a loss to owner and is negatively impacting astronomy, a compelling argument exists that regulating this waste light would be for the public good. Most uplighting is either unnecessary, or the same task (such as lighting billboards) can be accomplished by lighting from above.

There is a growing consensus in the lighting industry and among light pollution activists world wide that much of the outdoor lighting and the practices today are not only wrong but are counterproductive. The best example I can give you is the four/one rule. It says that you should not try to light an area beyond four times the mounting height of the light. When you do, often light is striking the ground at such a distance it is no longer useful illumination but rather is glare. When it enters the eye directly it can cause the iris of the eye to close and this is the opposite of what you want at night.

The best analogy I can give is something we have all encountered, and that is how hard it can be to see when we are driving during that magic hour after sunrise or the hour before sunset. The eye simply can't deal with a bright light source less than 15 degrees off of the horizon. Our eyes have trouble dealing with the glare of streetlights at night where the source can be seen beyond that four/one distance I have just mentioned, or less than 15 degrees up. It's like we have inadvertantly created a landscape of a thousand miniature setting suns at night with our older style street and area lights.

A full cut off shielding ordinance for all fixtures as is practical would greatly improve visibility by removing this veiling glare. With light on the scene rather than directly in the eyes of the observer, the ability to see at night improves dramatically. This is especially true for the sight impaired, older citizens, or people with cataracts, etc.

I would urge all of you to go down some of our city streets with the full cut-off cobra head flat-bottom fixtures that the city has begun to install and you will see what I mean. Good examples of this are Valley Drive south of the Toyota dealership, South Main, Boutz between Main and El Paeso, and Triviz on the west side of I-25 pass the city water tank going north.

Finally, some kind of lumens cap is needed to control excessive overlighting. The city of Flagstaff does this by a lumens cap per acre. This works for them as their Planning and Zoning need only check the specifications of the fixtures being installed during the permit process.

Based on their experience, I would recommend a 70,000 or 80,000 lumens cap per acre for fully shielded lighting. Pre-existing businesses in Las Cruces could be given a grace period to conform. After all, in many cases all we are asking them to do is take down some of the lighting. Along the same lines the retrofitting of shielding to bring existing lighting into compliance should not be open-ended but should have a reasonable target date.

What exemptions are allowed should be kept to a minimum and should be lumens capped in some manner. When you create a open exemption, exempt lights will proliferate without end. The porch light for example could be exempted as long as it is lumens capped so it may be used within reason.

Floodlighting, for example, could come under a larger shielded lumens cap as long as it was pointed down enough to obey the four/one rule. This would allow people to light their property but not their neighbors.

Simple rules really, not a real imposition to follow, but rules that could signifigantly improve our night enviroment, good neighborhoods, and would reduce the amount of light wasted to the sky by over half. We all will win with a well crafted lighting ordinance, win monetarily, win aesthetically, and win with a dramatically improved seeing at night. The stars, well we can just throw them in for free.