Dark Sky Ordinances - Learning Objectives

1. What is a Dark Sky & Light Pollution?
2. What is a dark sky light fixture?
3. What is a Light dome?
4. What are some light pollution solutions?
5. Where do I find dark sky lighting ordinance examples? Model Lighting Ordinance.

Dark Sky

Preserve our dark sky, at night, put light where it is needed, keep it warm, keep it dim.

In 1977, my home town of Orinda was planning a new park.  When I asked them to use Full Cutoff Luminaires, they requested something in writing to explain what and why I was asking; then I wrote my 28 page Outdoor Lighting Guide. The ideas behind this Dark Sky Lighting publication came from my Outdoor Lighting teacher, John Brass, the inventor of the full-cutoff segmented reflector, first used to retrofit the lighting on the Golden Gate Bridge. Thank you John Brass for teaching me how to control outdoor lighting.

When we use carefully aimed, dimmer lights - instead of excessively bright, glaring ones - we can see better, maybe even see the stars.  Balance and restraint is the key to most things in life, and restraint also applies to lighting, especially in our night sky.
Visit my Dark Sky page at TOlighting.com

What is Light Pollution?

The inappropriate or excessive use of artificial light – known as light pollution – can have serious environmental consequences for humans, wildlife, and our climate.
Lighting ordinances often include these components:

• Brightness - excessive light levels
• Glare – direct viewing of the light source that causes visual discomfort
• Sky glow – brightening of the night sky over inhabited areas
  
• Light trespass – light falling where it is not intended or needed
• Clutter – bright, confusing and excessive groupings of light sources

Malibu, California Dark Sky Ordinance

To see the October 14, 2018, Dark Sky Ordinance in Malibu California visit www.malibucity.org/705/Dark-Sky-Ordinance

Dark Sky Lighting Fixtures

Darksky.org Fixture Seal of Approval

What is a Dark Sky Light Fixture? 
The goal is to avoid sending light into the sky; therefore, we call it 'dark sky.' The specifics vary according to jurisdiction.  There are some basics qualities of dark sky lighting that seem universal. All light should be below the fixture, the light should be aimed down.

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Why Dark Sky?

International Dark Sky Organization www.darksky.org
Find a chapter near you and learn more.

Illuminating Engineering Society and International Dark Sky Organization Model Lighting Ordinance

IES + IDA - Model Lighting Ordinance 2011

Human Vision - Low Light, Color and Visual Perception 

It takes up to 20 minutes for your eyes to adapt to the dark, this is why overly bright light can adversely affect your ability to see, because you are literally 'blinded by the light.' As your eyes adapt to a dark sky, more and more stars will appear.
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​The chart above indicates the wavelengths for the spectral sensitivity range of each of the cone cells which together provide 'photopic' (daytime) vision, and the more sensitive rod cells which provide our 'scotopic' (nighttime) vision.

In low light levels, the sensitivity of the retinal cone cells tapers off, and the rod cells take over. There is only one type of rod cell, so the vision it provides is monochromatic and why by moonlight, we see only in 'black and white'.

Light domes measure light from cities at various distances : Mt. Dellenbaugh, Grand Canyon   http://www.nature.nps.gov/night/science.cfm

Light Pollution Solutions

Illinois Coalition for Responsible Outdoor Lighting

"One of our core principles is that responsible lighting practices must include consideration of each of the major areas of concern which commonly plague current outdoor lighting: Energy inefficiency and waste; unnecessary light trespass which impacts the natural environment, human health, and/or human experience of the night sky and night itself; and safety and esthetics. We believe that 'solving' one of these problem areas without addressing the others is a mistake." [1]

"To achieve the most effective outdoor illumination, and to minimize harmful side effects from that lighting, we need to have a good understanding of the nature of light, the effects of various types of light, and the light sources we use. Additionally, with the advent of a whole new generation of lighting -- the LED -- it is all the more important that we not only consider light quality, but use good information to guide the development and implementation of this new technology. " [1]

City of Davis LED Retrofit

City’s LED Retrofit Shows Need For Careful Lighting Choices
The initial LED streetlight installation went awry, but this story has a happy ending. Davis California, article by James Benya. [2]

To stop light pollution - turn off your lights. You can see the stars if there are no lights, like in Joshua National Park.

​Mexico’s Environmental Law Will Now Include Regulation of Light Pollution

The bill, called “Decreto por el que se reforman y adicionan diversas disposiciones de la ley general del equilibrio ecológico y la protección al ambiente” (“Decree for the reform and addition of various provisions of the general law of ecological balance and the protection of the environment”), was approved by the Chamber of Deputies (the lower house of the Mexican Congress) and is now set to become the official policy of Mexico. ​

The law amends and expands the General Law of Ecological Balance and Environmental Protection of 1988 (LGEEPA). It gives regulatory authority of light pollution to the Ministry of Environment and Natural Resources (SEMARNAT), in coordination with the Ministry of Energy (SENER). The law tasks these ministries with “the prevention of environmental pollution caused by intrusive light.”  ​ [3]

Warmer 3000 Kelvin required in revised zoning ordinance.

Fairfax County, Virginia: Changed outdoor lighting zoning ordinance to reduce glare. A typical incandescent bulb has a color temperature of approximately 2,600K. LED bulbs, which are becoming more common, are available in a wide range of color temperatures. Higher color temperatures are associated with increased glare, which can impact human health and wildlife. February 12, 2020 [4]

Related Topics

Landscape Lighting,  Dark Sky & Light Pollution, Dark Sky Reserves, Environmental Consequences of Night Lighting, LED Sources Kelvin, Astronomy & Dark Sky, Circadian System, 

Footnotes

1. Low Light Vision  Why does outdoor Lighting Matter? http://www.illinoislighting.org/index.html
2. City of Davis LED Retrofit http://darksky.org/citys-led-retrofit-shows-need-for-careful-lighting-choices/
3. Mexico's dark sky legislation  ​https://www.darksky.org/mexico-light-pollution-law/
4. Revised outdoor lighting ordinance requires warmer color temperature. 
   ​ https://www.fairfaxcounty.gov/news2/new-outdoor-lighting-standards-will-be-more-energy-efficient/​

Photo Credits

• Luminaire Shielding Designs Image ourtesy of Bob Crelin
•  http://www.illinoislighting.org/lightcolor.html
• @senadomexicano
• Kelvin 1000 to 10,000 Color Temperature Image courtesy of Fairfax County Government