1.  What has been the impact of light pollution on UK Astronomy?

  Light pollution grew considerably over the last half of the 20th century, primarily caused by the extensive spread of street, road and motorway lighting. When combined with more external facilities for leisure purposes, the ambient sky brightness (sky glow) has increased to such an extent that even in semi-rural communities the number of stars that can be seen by the naked eye, or even with a small telescope, is significantly reduced. Sky glow is the result of stray light from upwardly directed illumination or reflections off lightly coloured surfaces being further reflected off dust particles and pollution in the atmosphere.

  Even though most academic astronomical research is nowadays undertaken with telescopes at international sites overseas, there is much interest in astronomy in the UK, from both amateurs and professionals. All of these are increasingly plagued by intrusive illumination from advertising, sports facilities and upwardly directed illumination from street lights, which spoil star visibility. Many young people are encouraged to become scientists and engineers because of their interest in astronomy in their early years, but light pollution levels even in relatively remote parts of the UK are sufficient to spoil this activity. For example, many young people have never seen the Milky Way. Such a lack of opportunity could curtail their interest in astronomy, physics and science in general. The teaching of astronomy at University level is also threatened by the encroachment of light pollution on our visibility of the night sky.

2.  Are current planning guidelines strong enough to protect against light pollution?

  Existing guidelines are not hugely effective as Local Councils only have power over new developments requiring planning permission. This is adequate if current levels of pollution are to be significantly reduced. Additionally, planing guidelines do not normally cover fluctuating amounts of light pollution caused in various atmospheric conditions.

  With regards to new developments, more local authorities are imposing design criteria as set out by professional bodies such as the International Commission on Illumination (CIE), the Society of Light and Lighting (SLL), and the Institution of Lighting Engineers (ILE). In addition the "Campaign for Dark Skies" (http://www.dark-skies.org/) organised by the British Astronomical Society keeps a watch on major planning applications and encourages national companies to adopt a more responsible approach to external lighting. The remit of current guidelines needs to be extended to cover existing structures and conurbations to ensure that light pollution from these sources can be tackled in a similar manner. A list of relevant publications and standards in presented in the Appendix.

3.  Are planning guidelines being applied and enforced effectively?

  All new developments need to have an Environmental Impact Assessment (EIA), which includes the issue of light pollution. At this level, planning guidelines are generally observed, but it is believed that they are currently ineffective in controlling light pollution to the degree that would make a difference to UK astronomy.

  National regulation and legislation is necessary: frequently the pollution intrudes from a different borough which leaves a local authority powerless to act. The impact of light pollution from towns, villages and highways is not considered under current planning permission controls. It is the legislation rather than the "guidelines" that needs to change if more effective controls are to be implemented.

4.  Is light measurable in such a way as to make legally enforceable regulatory controls feasible?

  Light is measurable. The criteria have been established and generally accepted by lighting designers and planners alike. Low light levels can be measured in terms of intensity and spectra. Mobile detectors using similar technology to astronomical instruments could be designed.

  An almost weather-independent measure of sky glow, with an accuracy of around 10% is possible using reflection from the cloud base. Clouds scatter rogue upward light back towards the ground, except for the small amount that is transmitted. This can provide a reliable measure of light pollution above conurbations.

  On roads, light quantities are measured at surface level by sufficiently accurate photometers to ensure a required level for night driving. However, reflected light is not taken into account by highway engineers, and this can be a major source of light pollution. (Asphalt reflects less than concrete).

  Several countries already have in place legislation regarding light pollution:

  a.  The Czech Republic has recently introduced the Protection of the Atmosphere Act. This defines light pollution as "every form of artificial light which is dispersed outside the areas it is dedicated to, particularly if directed above the level of the horizon". Citizens are obliged to "take measures to prevent the occurrence of light pollution in the air" or face fines. Authorities are required to use fully shielded lights to control the spread of light, and use flat rather than curved glass to prevent light dispersing upwards and sideways. Advertising billboards will have to be lit from above, with their lights pointing downwards.

  b.  In Italy the Lombardy Parliament has passed a light pollution bill making it illegal to install light fixtures emitting a light directly above the horizontal, and near amateur and professional astronomical observatories all the lighting should be replaced within four years.

  c.  Catalonia has a Law on Environmental Planning of Outdoor Lighting for the Protection of Night Darkness, preventing excess light pollution from escaping into the sky.

  Many European astronomical bodies are preparing an approach to the European Parliament stating that this world-wide problem needs addressing as part of a much needed enforcement of energy saving policies already agreed at the international level.

5.  Are further controls necessary on the design of lighting?

  There are various measures that can be put in place regarding the design of lighting to combat light pollution. Sky glow, which is caused by stray light reflecting off dust and pollution in the atmosphere, can be reduced by improving lighting design. However, it would be difficult to keep down the sky glow above towns and cities to levels where good visibility is provided for amateur astronomers. Also since one of the major light polluters is street and road lighting it will take some time before all non-conforming street lighting can be replaced. The situation in rural and semi-rural locations could be improved much more readily provided all industrial, commercial and residential developments, as well as road and street lighting, had the light pollution criteria applied, without exception.

  Additional guidelines for residential dwellings should be considered. Commercial external lighting comes under the scrutiny of planners, and this is usually carried out by professional lighting designers. However, there is nothing to stop small businesses and domestic properties from installing external lighting in a completely uncontrolled way: only freestanding structures carrying lighting fixtures normally come within the control of a planning authority as they are deemed to represent "development" as defined by the Town and Country Planning Acts. It would be very advantageous to have controls on the extent of uplighting (towards the atmosphere) from outdoor sources, and also from light sources shining nearly horizontally towards a highway. If upwardly directed illumination could be significantly reduced it would substantially reduce light pollution,

  New regulations could be introduced to put some control over this part of the market both from pollution and energy points of view. The majority of external lighting fixtures used for security and external lighting on domestic dwellings tends to be 500W linear tungsten lamps. These lamps are inefficient. Inefficient lighting results in wasted energy and global warming, giving a case for regulation regarding both light distribution and energy efficiency.

  Whether or not the degree of reduction required to improve significantly night-sky visibility in the UK would be acceptable to the general public is another matter. Whilst no one would defend inefficient or unnecessary lighting it must be said that well-designed external lighting is believed to improve safety and security and enhance the "urban experience". In general it is felt that whilst there is a case for placing some kind of limit on light pollution, this is more easily justified on the grounds of energy efficiency than astronomy, since it is assumed that the future of astronomy using visible light lies with extra-terrestrial telescopes such as the Hubble Space Telescope. Any restrictions on external lighting must be balanced against the public's perceived need for improved safety and security, particularly in the urban environment.

  There are additional remedies that could reduce light pollution. Having a cleaner atmosphere with lower concentrations of pollutants would help, as would reducing vehicular traffic.