Light Pollution

By Lachlan MacDonald

The ASNSW has, as one of its major objectives, the enjoyment of the night sky. With this in mind, the ASNSW tries to make its Members and the general public aware of the effects of obtrusive outdoor lighting, and light pollution problems in general.

The effects of light pollution impacts on astronomers, in particular, because of the way it diminishes the view of the night sky. In most major cities, such as Sydney, the night sky is almost invisible to the naked eye apart from a few of the brighter stars. Light pollution, while not as well-known as some of the more toxic pollutants, such as oil, chemicals and plastic bags, etc., is nevertheless still a major concern.

Can it be classed as a form of pollution? Most definitely YES! Light pollution can actually wash out the view from what is perhaps the greatest natural wonder of all – THE NIGHT SKY!

Light pollution is an insidious form of pollution because it disappears as soon as the offending light source is switched off and leaves behind no foul substance or filthy residue. The awareness of this form of pollution is becoming increasingly prominent in major urban populations as more and more people realise that they can no longer see the night sky. When New York City suffered blackouts in 2003, many people were left agog at the views of the night sky. Many were not aware that the night sky contained so many stars!

In Australia, the effects of light pollution are not as severe as they are in countries such as the United States. However, our cities and urban areas suffer greatly from the effects of obtrusive lighting. As you can see on the world map below, Europe and the USA, along with parts of Asia, are awash with lights, which greatly affect the enjoyment of the night sky in these areas of the planet.

Global Artificial Night Sky Brightness

Map courtesy of Instituto di Scienza e Tecnologia dell’Inquinamento Luminoso

There are three major forms of light pollution

  1. The first is sky glow. You can notice this at night, when the clouds overhead start glowing pink, white or orange in colour. This is caused by all the light that is wasted from inefficient light sources. These wasteful light sources usually come in the form of poorly-designed or improperly-aimed light fixtures. The light thrown off by these sources is just wasted energy, as it does not benefit anyone with it spilling out into the night sky. The problem of sky glow directly affects the visual view of the night sky. It also impacts on the scientific research of amateur and professional astronomers.
  2. The second form of light pollution is known as light trespass. This is caused when illumination from light sources crosses from one property to the next. Most of you reading this would have experienced this form of light pollution, usually when another person’s lights shine through your window at night. This can be quite irritating, as it is light trespassing onto your property. This has occurred at the ASNSW's Wiruna dark sky observing site when one of the neighbours has placed lights outside at night and not screened them properly. From other more urban areas, it degrades the view of the night sky when you go outdoors to view the Cosmos in all its glory.
  3. The third major problem with light pollution is glare, which is caused by too much lighting being applied to an area. Glare is recognised as a visible source of illumination that causes a reduction in your visual performance. Try looking into a bright light and see how much you squint – in most cases it can actually hurt. In extreme cases, such as looking at the Sun without proper filters, it can actually permanently damage your eyesight.

Light pollution has become a major menace to amateur and professional astronomers alike. However it can be minimised through the use of properly-designed lighting that neither compromises safety nor impedes the wonderful view of the heavens. Many communities around the world are becoming more aware of the problems associated with excessive and wasteful forms of lighting, and they are beginning to adopt ordinances in their areas to aid in the improvement and control of night-time lighting requirements.

Figure 2 (below) is a photograph of the night sky taken by ASNSW member John Sims. John was taking a wide-field shot from the western observing field at the Wiruna dark sky site, when the headlights of an approaching car ruined the photograph. The headlights caused the light green haze extending from the top left of the photograph.

Headlights destroy astroimage

Photo courtesy of John Sims

Some Easy Solutions To The Above Problems

  1. Use the right amount of lighting. Don’t overdo it. Why use ten lights when one will suffice quite nicely?
  2. Make sure your lights are shielded so that they shine down or upon the area requiring illumination, not upwards or away from where it is required.
  3. Install timers on any lights so that they are only on when they are needed.
  4. Use low-pressure sodium light where possible, as it is the most energy efficient form of lighting. Also, pollution from this type of lighting can be minimised with the use of telescope filters.
  5. If you see good-quality lighting around, let the people concerned know that you appreciate their lighting arrangements.
  6. Try and educate other people about light pollution and the adverse effect it has on the night sky.

Observing Etiquette

Have you ever been to a dark sky observing site such as the ASNSW's Wiruna property? If you have, you would have also learned how to minimise light pollution at night. Members who attend Wiruna on a regular basis are aware of the need to shield any obtrusive lights, as it may ruin another observer’s view through their telescope. This is where some simple “Observing Etiquette” can save you from the wrath of keen deep-sky observers.

Here are some simple things to consider:

  1. The simplest of all – DON’T USE WHITE LIGHTS! Use red lights only (and that does not mean a bright torch with one measly layer of red cellophane).
  2. Make sure your car does not light up like Pitt St when you open the car door during an observing session.
  3. If you arrive late and need to set up, do not use a 100W+ light to do it. Let any observers know you need to use a white light for a short time if need be (you may have lost that important screw in the dark!).
  4. Watch your step at night, but don't use a bright torch to see where you are going. If the sky is clear, the stars are out. Once you have let your eyes become adapted to the dark, it will be quite easy to see where you are going at an observing site like Wiruna. It is actually easier to see without a torch, especially if you have been out observing for a while.
  5. If you are a new visitor to a dark sky site, try to arrive early and familiarize yourself with the layout so, when it is dark, you will have a “feel” for the area.
  6. Remember that a dark-sky site is primarily for observing or photographing the night sky. Inconsiderate use of white light defeats the purpose of that facility. Many people travel long distances to get away from obtrusive lights.

Light Pollution Issues in Australia

Most of the electricity requirements for major Australian cities are met by coal-fired power stations, or basically fossil fuels. Light wasted in a major city such as Sydney amounts to many millions of dollars. As well, many thousands of tons of carbon dioxide emissions are spilled into our atmosphere as a result of all this wasted energy. Stray light can also disturb the natural day-night cycle experienced by wildlife populations, causing distress and upsetting their balance.

Most of the poor lighting issues effecting Australia can be overcome by carefully considering the areas that need illumination, then finding properly shielded and energy-efficient lighting fixtures to suit that situation. For example, streetlights can be replaced by full-cut-off fixtures, which ensure that light is directed downwards where it is needed. They can also be fitted with energy-saving lamps. Lighting needed to illuminate signage should be directed downwards, not upwards into the night sky. Security lighting should be fitted with efficient lamps and shielded so that light is directed to the required area. Floodlights in residential areas can also be shielded quite easily to stop light trespass and light being emitted upwards. Home owners should avoid over-lighting an area where possible.

The outdoor lighting standards in Australia are surprisingly not too bad. Although some councils comply, most business premises and private institutions still have no interest in complying with the standards. Many countries around the world are increasingly adopting lighting controls, which carry with them vast savings in energy. A country such as Australia, which has a rich astronomical history and a strong base of amateur and professional astronomers alike, should be at the forefront of the major issue of light pollution.

Australia detail

Map courtesy of Instituto di Scienza e Tecnologia dell’Inquinamento Luminoso

Some Light Pollution Links

Map images courtesy: P. Cinzano, F. Falchi (University of Padova), C. D. Elvidge (NOAA National Geophysical Data Center, Boulder). Copyright Royal Astronomical Society. Reproduced from the Monthly Notices of the RAS by permission of Blackwell Science.


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