article: Preserving Ireland's Dark Skies

By Albert White, ILPAC

Many of us who live in urban areas can not see the Milky Way with the unaided eye, sights like those captured by Keith Geary showing the beauty of are home galaxy are lost to all except those living in the darkest skies. In the worst cases some of us in Dublin have trouble seeing more than a handful of stars. The reason is that instead of a perfectly dark sky we are seeing the glow of badly designed streetlights and badly installed security lighting - Light Pollution.

There are three forms of light pollution, all of which are troublesome to astronomers, though as we shall see some affect much more than just us stargazers.

Sky Glow, the orange glow that can be seen in the night sky above Cities, this is particularly apparent in the South Dublin hills where one can contrast the view of the sky over the City with the view over the mountains. Any light shining over the horizon contributes to this glow and the effects can be seen from many miles away from the polluting lights.

Glare, this is light shining into the eye preventing a person from seeing the illuminated are properly. For example a car with full headlights on will dazzle an oncoming driver, similarly an over powerful security light at the wrong angle can do the same.

Light Trespass, this is where the light is not only illuminating its target area, but also lighting another area where it is not wanted. This is most commonly found with security lights shining over a wide area.

These forms of light pollution are illustrated in following diagram:

[Fig 3]
Image courtesy Institute of Lighting Engineers

All three forms of light pollution can be simply summed up as light being directed where it is not supposed to go, whether it is a security light shining over your property, or `designer` lighting shining high powered lights directly upward as can bee seen on the cover of the December 2003 cover of A&S.

However its not only astronomers that are effected. There is increasing evidence that wildlife is affected by light pollution, with or example birds singing throughout the night. And in parts of the USA where sea turtles lay eggs on beaches, many are found dead or in need of help as a result of getting disorientated by nearby lights.

Luckily in Ireland the problem is not as severe as it is in other European countries. Satellite images show a concentration of lights around our major cities and towns, but rural areas are still relatively dark. However to get away from the effects of light pollution you have to travel far from population centers, members of the South Dublin Astronomical Society regularly travel to locations throughout Wicklow, on average 40 kilometers from central Dublin to get away from the sky glow from the capital, and at that distance the glow from the city is still very evident on the northern skyline.

Some of you may have felt the sense of frustration in the past as I have of writing to your local Council to complain about light pollution, and getting an unsatisfactory response. So earlier this year I asked around the astronomy clubs in the country to see if there was any Irish Organisation, like the UK based `Campaign for Dark Skies` which was dedicated to reducing light pollution, and I soon was put in contact with some like minded individuals, mainly from an environmental background, who were trying to reduce light pollution and educate people about better lighting.

This group is now the `Irish Light Pollution Awareness Campaign` and has members from all Astronomy Clubs in the country as well as several environmental groups. ILPAC was formally launched at the 2003 Whirlpool Star Party in Birr last September, and we were fortunate enough tohave David Levy, the well known comet hunter and a director of the `International Dark Sky Association` (, of which ILPAC is the Irish section, in attendance.

This article is hopefully preaching to the choir, as amateur astronomers you all know that light pollution is bad and should be cut down. However using the argument that amateur astronomers cant see faint fuzzy objects in the night sky is not going to convince anyone to change planning regulations or retrofit lights. So how can we advocate change?

There are many good reasons to reduce light pollution, preservation of the night sky, it would be better for wildlife, to reduce glare shining into offices and onto roads etc. however there is only one reason that will convince those who can make the changes. Bad lighting costs money, good
lighting is cheaper!

In 2001 the city council in Calgary, Alberta, Canada, approved funding to retrofit all approximately 33,000 cobrahead residential streetlights from 200watt drop dish fixtures to 100watt, flat lens fixtures. The old lights send some light horizontally and even some upwards into the sky but the new full cut off lights will redirect all light towards the ground, allowing the city to maintain acceptable illumination levels despite the reduced bulb wattage. To date approximately 18,000 lights have been refitted. The principal driver for this $7.8 million Canadian project was to reduce energy costs and save money, the other factors such as environmental issues, reducing light pollution although important were secondary to the project. It is estimated that the project will pay for itself in three to four years. Retrofitting all the bad lights in Ireland immediately would cost money, however these lights need replacement every few years anyway, and provided the new lights are non-polluting then there is no additional cost. This is already happening in parts of Dublin where the familiar orange low pressure sodium lights are being replaced as they require maintenance with high pressure sodium lamps which can be directed directly downwards. We would prefer if these were flat glass lights rather than the more polluting bowl lights that are being used, but it does show an awareness of the issues and a willingness to tackle the issues.


What you can do?

There are two ways you can help reduce light pollution. Firstly try to light your premises better, and encourage your friends to do the same, every light makes a difference.

Check that lights are pointing directly downwards, pointing them at any angle results in light going above the horizon and into the sky. In many cases, such as with conventional halogen security lights, this can be done easily without many need to invest in new light fixtures. As you need to replace older light fittings, use ones that can be directed directly downwards. Please contact us if you would like more information on how to better light premises.

Consider timing your lights to go off at a certain time, or using motion sensors to ensure the lights are not on the whole time. We have found that some companies are happy to turn most of their car park security lights off at night when there are no cars there for example, or using motion sensors to ensure lights are on only when needed.

I should point out that in addressing the issue of light pollution there is no need to compromise traffic safety or to make people feel any less safe in their homes or when they are walking at night. ILPAC are not advocating that all lights be turned off merely that they be directed downwards so they do not waste electricity lighting up the night sky.

Secondly you can join ILPAC! Everyone is welcome to join (its free!) and details on our mailing list and discussion boards are on our webpage ILPAC is a resource that is there for you if you want help or advice in writing to councils or companies about their lighting practices. We are particularly interested in hearing from people who would like to take an active role by keeping an eye on local planning applications and development plans and giving talks and presentation to local groups, if you are interested please email us at

You may also be interested in joining the International Dark Sky Association, of which we are the Irish Section, more details can be found on


What ILPAC wants done

Getting lights retrofitted is only part of the problem however, there are other issues that need to be addressed to tackle the problem of light pollution. In Particular ILPAC is asking Councils, developers and the Government to adopt the following proposals:

  • Insist on a light pollution assessment at the planning stage of new developments. Badly designed or over-lit schemes should be sent back to the applicant for modification. Interested parties should be able to object to proposed plans based on the proposed lighting. Where an environmental impact statement is required for major developments, ensure that they address light pollution.
  • Setting limits on light pollution, including operating times, according to the remoteness, darkness or other special qualities of the area. There should be a strong presumption against any powerful and intrusive exterior lighting schemes in or near the less built up areas.
  • Set targets for replacing all street lights with less light polluting types. This can be done as the lights are scheduled for normal maintenance and replacement. Street lights are among the highest contributors to light pollution in the area. As part of this program the council should consider reducing the number of streetlights in over lit areas.
  • Introduce guidelines for exterior lighting requesting that all public, commercial and residential exterior lighting should point directly downwards to minimise light pollution.
  • Recognise light pollution as a real problem, and introduce legislation similar to that for noise pollution. Currently you cannot legally object to a security light shining into your home.

Recently a Select Committee of the UK parliament published a report on light pollution, advising the government there to take steps to reduce the problem, and recently Tony Blair was asked about the issue in the House of Commons. In Ireland several County Councils are considering introducing light pollution guidelines into their development plans. So we are slowly making progress! But we need your help so please sign up to our mailing list at, or contact us directly at

Albert White is Deputy Chairperson of ILPAC, member of the International Dark Sky Association, and a member of the Irish Astronomical Society. He can regularly be found in the Wicklow mountains on clear nights observing and cursing the street lights of Dublin!


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