Proud Organization Member of the
International Dark-Sky Association

Stars Up Lights Down

The Durham Region Astronomical Association
Light Pollution Abatement Committee

Description of the Problem

We need to get . . .

From This . . . To This . . .

The image on the left, above is what a typical sky looks like from a city or large town. The sky is ablaze with light that has been needlessly allowed to shine up where it serves no useful purpose.  This wasted light is wasted energy, and this wasted energy was produced with fossil fuel that created greenhouse gas, which in turn leads to global warming and climate change.  Moreover, the stars that were once visible have now disappeared from view.  With properly installed and appropriately used outdoor lighting, this sky glow can be significantly reduced to bring back the view of the majestic sky, as shown in the image on the right, above. In the process we save energy, reduce our dependence on fossil fuels, and realize reductions in greenhouse gas emissions, and that helps to take action against climate change.

Components of Light Pollution:

Light trespass - Spill light coming from another property.
Glare - From seeing the bright filament of an unshielded light, troublesome and dangerous.
Clutter - Excessive grouping of lights, causes confusion as well.
Energy waste - Costing us over nearly 2 billion dollars per year in North America.
Urban sky glow - Domes of light over cities. Blocks out faint objects such as the Milky Way, galaxies. Only a few bright stars can be seen from the city.

Light Trespass:

Light from an unshielded fixture that is suppose to be illuminating the ground is also casting light upward. This is wasted light and wasted money. Some fixtures spill light onto other properties. This can be prevented by taking care in the placement and alignment of the light.

Glare:

Generally speaking, if you can see a light’s filament or source from a reasonable distance then the light is not well shielded.

The glare from an unshielded fixture can compromise visibility and increases the chance for accidents. Bright glare can also produce high contrast shadows. These shadows actually become corridors of darkness that can become hiding places for potential criminals.

Clutter:

Excessive glare can make driving difficult and light clutter can cause distraction. For safety reasons every effort should be made to establish quality lighting on and near heavily travelled roads. Billboards and outdoor signs are designed to attract our attention. Often these are lit up with bright flashing lights, and/or lit from the bottom which allows much of the light to spill up into the night sky. These light sources add considerably to the overall light pollution.

Energy Waste, Greenhouse Gas, Climate Change:

A night time aerial view of a city reveals how much energy we waste by using unshielded lights. Any direct light sources that can be seen from above are contributing to a waste of energy and the precious limited resources that produce that energy. Moreover, a significant amount of greenhouse gas and air pollution was produced to create that wasted energy. It is now acknowledged by world governments that greenhouse gas has an effect on global warming, climate change and human health.

By reducing the amount of upward (wasted) light we can help to extend our overall energy pool, which makes good economic sense, reduces greenhouse gas production, helps deal with climate change and reduces respiratory-related deaths and illness caused by air pollution  .

Sky Glow:

This is the bane of astronomers and anyone that wants to see the night sky for its infinite beauty. The combined output of all the lights in a city cause the sky to be washed out. Stars and other objects, such as the Milky Way and galaxies, become increasingly impossible to see.

Sky glow is rapidly becoming worse. We must start now to encourage quality lighting. Reducing the upward shining light will help eliminate light pollution. Our children need to be able to see the stars. They are the ones with the eager questions and imaginations that will shape our future!

The night sky is no less deserving of protection than other significant natural features.  The night sky must be protected as a heritage resource having natural value and scientific interest.

Types of Lamps:

Low Pressure Sodium (LPS) fixture produces a yellow tint.
High Pressure Sodium (HPS) fixture produces a pink tint.
Mercury Vapour fixture produces a blue/white tint.
Incandescent light (bulbs) produces a yellow/white tint.

The first three types are a gas discharge source. The light is produced when the electric current passes through a container of gas, causing the energized gas to give off characteristic bands of colour.

In an incandescent source a thin wire is heated to a high temperature by an electric current. This filament begins to glow and gives off light of many colours. A large amount of energy is given off as heat making the incandescent source not as efficient as the discharge source.

55 watt LPS = 100 watt HPS = 175 watt Mercury Vapour = 400 watt incandescent

For less energy a 55 watt LPS fixture can produce the same amount of lumens (light output) as the 100 watt HPS, the 175 watt Mercury Vapour and the 400 watt incandescent.

For more information, see our links page.

Some Easy Solutions:

• Use the right amount of light, not overkill.
• Shield the light so that is goes down, not up or sideways.
• Use light timer controls whenever possible.
• Use LPS fixtures whenever possible because it is the most energy efficient and because its light can be filtered out with telescope filters.
• Avoid using round globe lights unless they are properly shielded.
• Be aware of quality lighting. Let people know when you see some good and attractive lighting arrangements.
• Educate other people about the adverse effects of inappropriate lighting.

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