Light Pollution

Lights of Bainbridge Island

As a tax-exempt non-profit organization with a commitment to Bainbridge Island public service including astronomy education and observatory operations, and having constructed a large telescope with donated funds, the Battle Point Astronomical Association is working with the International Darksky Association (IDA) to help raise awareness of the issue of light pollution. This page helps make information available that covers effective and efficient security lighting, energy saving, lighting codes, and many other topics.

  • On January 1, 2003, the City of Bainbridge Lighting Ordinance went into effect!
  • On March 21, 2001, Bruce Weertman, Chairman of the NW Region of IDA, spoke at the Ritchie Observatory on fighting light pollution. In attendance were several Bainbridge Island City Councilmembers and the Mayor.
Why do we need outdoor lights?

Outdoor lighting is used to illuminate roadways, parking lots, yards, sidewalks, public meeting areas, signs, work sites, and buildings. It provides us with better visibility and a sense of security. When well-designed and properly installed, outdoor lighting is very useful in improving visibility and safety, while at the same time minimizing energy use and operating costs.However, if outdoor lighting is not well-designed and properly installed, it can be costly, inefficient, create glare and harm our nighttime environment.

Have you ever heard of light pollution?

It is a growing threat to the nighttime environment. Components of light pollution include:

  • It is a growing threat to the nighttime environment. Components of light pollution include:
  • Glare, blinding pedestrians and drivers and harming visibility. Glare is never good.
  • Energy waste, costing over one billion dollars a year in the USA alone.
  • Light trespass, outdoor lights that trespass onto other’s land.
  • Urban sky glow, which is destroying our view (and our children’s view) of the universe (it would be a shame if our children thought that the Milky Way was only a candy bar).

There are solutions to all of these problems. Quality lighting is the key. These solutions preserve the dark skies for all of us, improve the quality of nighttime lighting (better visibility, better safety and security, more attractive surroundings) and save money as well as we use light rather than waste it. We all win!

You can help! Here’s how:

First, become aware. Insist on quality lighting. Use it yourself. Awareness of the problem is lacking, even among some lighting professionals. Quality lighting is well shielded (so the light is used, not wasted), uses the right amount of light (not overkill), and includes the use of energy efficient lighting sources. Such quality lighting is directed downward where it is needed, not up or sideways where it is wasted and causes glare, light trespass, and bright skies.

Light Fixture Diagram
Here are some suggestions:

Security lights: Use motion sensors. If the primary purpose of a light is to provide security, place a motion detector so that it comes one whenever someone enters the area. Since the light is turned off when it isn’t needed, money and energy is saved. An intruder may be startled by the light suddenly coming on and leave.

Roadway lighting: Low pressure sodium is the most energy efficient and astronomy-friendly type of lighting. However, high pressure sodium in a full-cutoff type fixture can produce better lighting and less sky glow in some applications. The newer flat bottom fixtures are gradually replacing the older style cobra heads that emitted most of their light sideways and created significant glare.

Signs: Signs should be illuminated from the top, not from the bottom.

Wattage: Use the right amount of light, not overkill.

Inexpensive Modifications: Some lights, such as the NEMA fixtures depicted above left, can be easily retrofitted with an inexpensive cap. If even that is deemed too costly, the inside of the fixture can be painted with aluminum paint or covered with silver duct tape — which will increase the useful light and decrease the wasted light.

Lighting fixtures: Much light emitted by some fixtures comes out at angles where it is of no use in illuminating the ground or the area where light is needed. Consider an angle of 0 degrees as directed straight down to the ground. An angle of 90 degrees is therefore sideways, parallel to the ground, and an angle of 180 degrees is straight up. Light emitted at an angle of greater than 90 degrees is uplight, and it is a cause of urban sky glow. Light emitted at angles between 70 and 90 degrees does very little in illuminating the ground, for it would not strike the ground for a long distance from the source, and it is so faint by then that its effect in illumination is nil. However, it produces a great deal of glare — direct light striking the eye and dazzling or blinding the viewer. Any light at higher than 70 degrees is wasted, as is the energy to produce it. Full-cutoff fixtures are preferred as they eliminate wasted light.