Where to Find Light Pollution and How to Eliminate it

I previously , some of the serious environmental consequences of light pollution. 

As promised, this entry will describe how we, as individuals, can do our part to eliminate, or at least reduce, light pollution that we produce.  But first, we need to know where light pollution comes from and who is responsible.

In general, there are three responsible parties that produce light pollution:

Governmental Level Organizations: Streetlights, Area Lights, “Security” Lights, and Building Lights
Commercial: “Security” Lights and Building Lights
Individual: “Security” Lights and Building Lights

I took the September 8^th power outage that affected the southwestern United States as an opportunity to photographically demonstrate the presence and location of these types light pollution sources in a section of Poway.

I was also inspired by link provided by loyal reader to the online cameras on the top of Mt. Woodson, showing the light pollution emanating each night from Poway and beyond.

(It helps to now look at the images associated with this blog entry)

These are links to the higher resolution versions of the images that cannot be posted here due to size restrictions:

Mt. Woodson Camera Composite
Power Outage Overlook

If you look closely, you will see that Poway does not have much light pollution coming from streetlights when compared to parts of San Diego, because the Poway had the foresight to use shielded lights for roadway lighting.  Sadly, the lighting ordinance within the Poway Municipal code, Section L to govern light pollution, is a far cry short of the Model Light Pollution Ordinance (pdf).

I hope it is clear to you, from the images to the right, and their captions, that a great deal of the light pollution present can be controlled or eliminated, by us, as individuals.

Here is a link to an IDA .pdf file that will give some additional details, that I cannot go into here, about what you can do about local sources of light pollution that you can directly control.

For all of the complex reasons for the negative impacts of light pollution, all of the very advanced and technical means of measuring light flux and calculating biological responses, all of the various doctoral degrees issued in fields related to this, the fix comes down to two simple words:  Timing and Shielding.

Not turning on the lights, while the most effective solution to eliminating light pollution, is not practical because there are often very good reasons for illuminating outdoor areas at night.  But that illumination is almost never needed for the entire night.  The use of timers and/or motion sensors can keep the lights on when you want them, and off when you don’t.  Illuminating non-target areas at the wrong times is simply a waste and is accurately described as "dumb lighting".

In fact, the use of motion sensors on security lights enhances their security function because criminals do not fear the light, they fear the change in the light.

Shielding is equally important, particularly for lights than cannot be quickly cycled on and off (eg metal halide), in that they help to keep the light inside the target area, and through their reflectors, make the most use of the light being generated to start with.

Diagramed to the right is a typical unshielded light that shows that ~60% is wasted in the form of glare and light pollution.  This is the light that you see from the mountaintops in the photos.  That’s money burning a hole in your wallet.  It’s desirable wildlife making a beeline away from the area.  And it is the source of a whole host of longer term “slow” problems building up.  It also means that you need a more than 2x the energy get the originally desired amount of light in a specific area.

As a general rule of thumb, you can tell if a light fixture is fully shielded by looking at the light source horizontally from the lowest part of the upper shielding section.  (ie the shielding material that prevents the light from going up into space.)  If you can see the light source (the bulb) then the light fixture will cause light pollution.  If you cannot see the bulb (the bulb is recessed) then the light fixture will not likely produce light pollution.

There are two methods of having properly shielded lights:  Installing pre-built shielded light fixtures, or retrofitting your current fixtures.  Like in all things, making decisions such as these early in the planning phase of any project requires less physical work than fixing problems later on.  There are numerous companies that sell fully shielded light fixtures (in styles to fit all tastes), so most of the work has been done for you.

One of the easiest ways to determine if a light fixture complies with the standards to eliminate light pollution is to use IDA website resource that certifies light fixtures for residential and security lights that meet the required criteria.

These products have enclosures that ensure that the light you want is put in the places you want it, any nowhere else.  They use reflective material to take the light that would normally blast into the sky, the surrounding wildlife, and blind you with glare, and redirect it to the target area.  This vastly increases the efficiency of the fixture, and cuts your energy bill.

To be clear, I have no connection, financial or otherwise, with any of the links presented above.  These links are not comprehensive and with little effort, I am confident you could find more.

But what happens if you already have invested in a light fixture, how to you perform a retrofit to make the light emit less light pollution?

The only choices I have been able to find to address this issue are to install a motion sensor on the lights or start a new "art" project.  Motion sensors will work with fluorescent (common), incandescent (common), and LED fixtures (gaining popularity), but will not work with metal halide lights (mostly “security” lights). 

I’d love to give you links to kits to retrofit your non-shielded light with shields, but I don’t think they exist.  Your only choice (other than fixture replacement) is to construct a shield out of easily available materials.  (wood, sheetmetal, plastic).  This is a simple project that can be fun, and just involves building and installing a small cap over the top of the light, extending outwards far enough that the bottom of the light source is not visible from any angle above the horizontal.  (See the image)  I've seen shields made of rain gutters, of sheetmetal, and extended overhangs.

Next time I will go into “insecurity” lights and how to make them work the way you want them to, turning them into security lights.