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By Helen Walker

Many scientists were drawn to their careers by the excitement of observing the night sky, either the wonder of the thousands of faint stars in the Milky Way or phenomena such as comets and meteors, planets, aurorae, and these are now lost to the young due to light pollution. The Astronomer Royal, Professor Sir Martin Rees, has said, "we may not all be ornithologists but we would miss the song birds in our gardens."


What is light pollution?

Most of us have experienced light pollution in one way or another, either a neighbour's intrusive security light, glare from the lights in a car park, or perhaps that wonderful surprise of looking up at the night sky from a remote beach or hillside on holiday and seeing the Milky Way (possibly for the first time in years).

There are several aspects to light pollution:

  • Light trespass: Light that shines from one property into another where it is not wanted.
  • Glare: Light that shines into the eye, preventing a person from seeing the illuminated scene properly.
  • Confusion: Too many bright lights (also flashing lights) competing for attention.
  • Light waste: Lights left on (all night), too bright light for the task in hand.
  • Sky glow: The bright sky over our town and cities, caused by light shining up and not down.


What has been the impact on UK astronomy?

For many years, astronomers have been very concerned about the impact of increasing light pollution on the study of astronomy, the observation of astronomical phenomena by professional scientists and amateurs, and the loss of the night sky as a trigger for scientific interest in young people. Many people and local astronomical societies have their own telescopes. There are around 100 universities in the UK, and about half of them offer significant modules in astronomy at undergraduate level. Around 25 universities carry out significant astronomical research (i.e. have grants from PPARC). The Society surveyed its own points of contact and found that there are around 33 observatories attached to universities, ranging from small roof top telescopes for undergraduate viewing up to telescopes at the 1 metre size used for some research. The compromising of these facilities in the UK means that students find it hard to get the appropriate training in the observational techniques of astronomy, and instruments have to be taken abroad for testing (which is expensive). It is not possible to take students to Hawaii to teach them how to use a telescope.

The Society for Popular Astronomy queried its members and found (from more than 800 returned questionnaires) that nearly 80% of them cannot see, or can only barely see, the Milky Way, and well over half of them have to travel between 5 and 50 miles to find acceptable viewing conditions (one in eight people had to travel more than 50 miles).


Is it just visible light that pollutes?

The UK needs to be vigilant about the associated issues of radio frequency interference and pollution which could curtail the work of the Lovell telescope at Jodrell Bank, the MERLIN radio telescope network in the UK, and the UK radio telescopes' work internationally (for example, as part of the Very Long Baseline Interferometer network).


Is this just a UK or European problem?

Optical astronomy has already suffered from space-based pollution, caused by the Iridium satellites and by space debris, just as radio astronomy has been inhibited by the Russian GLONASS satellites, which transmit sideband interference. The RAS formally protested to the Director General Space Regatta Consortium about the Znamya-2.5 space mirror experiment in 1998. The International Astronomical Union has passed resolutions at eight general assemblies on the issue of light pollution and related matters and in 1999 the International Astronomical Union and the United Nations Special Environment Symposium 'Preserving the Astronomical Sky' made several recommendations to Member States.

The International Astronomical Union (IAU) has expressed concern about:

  • future space projects seriously interfering with astronomical observations in the optical and radio domain,
  • protection of astronomically important radio frequencies,
  • vapour trails from aircraft affecting astronomical observations,
  • satellite-borne reflector and solar-reflector systems,
  • the contamination of space (with debris),
  • the protection of observing conditions at the remaining excellent sites on this planet, and requests authorities to ensure the night sky receive no less protection than has been given to the world heritage sites on Earth.

Other countries have produced guidance and legislation for the control of light pollution including Calgary, Lombardy, Canary Islands, Catalonia, Czech Republic, parts of Japan, several states in the USA.


What can the Authorities and Government do?

Paul Murdin (in the Observatory Magazine, volume 117, page 34) proposed a scheme to classify sites where astronomical observing takes place (ALCORs), so that local authorities would be aware of them, and their significance. They are adapted for astronomy from a zoning system produced for the Institution of Lighting Engineers (by Nigel Pollard), based on environmental considerations. The proposal is that the defence against light pollution would be drawn up for each ALCOR, to progressively more stringent standards.

  • ALCOR 0: No astronomical activity is practical from such a region. Examples: urban entertainment areas, motorways, industrial zones.
  • ALCOR 1: Casual sky viewing of planets and constellations is possible, including from public (city-centre) observatories, schools and colleges (with telescopes around 30 cm in diameter). Examples: suburban, residential districts in general, recreational (park) areas.
  • ALCOR 2: Special types of observing (avoiding light pollution) such as infrared observations, high-resolution spectroscopy of bright stars, and other observations are undertaken by undergraduates or 'expert' amateur astronomers at university or 'museum' equivalent sites (with telescopes around 50 cm to 1 metre). Examples: particular places in urban, suburban, town locations.
  • ALCOR 3: Photometry and intermediate-resolution spectroscopy, could be undertaken by professional or 'expert' amateur astronomers to a high standard (with telescopes around 50 cm to 1 metre). Examples: selected near-rural or rural locations.
  • ALCOR 4: Narrow-band imaging, imaging in general, low-resolution spectroscopy, could be undertaken by professional astronomers for wide-ranging programmes to the highest professional standards. Examples: national parks, remote, selected rural locations, probably the darkest sites in the UK.
  • ALCOR 5: Wide-field imaging, low-resolution spectroscopy of faint sources, professional work from a site with rare quality. Examples: very remote locations, of which there are very few in the world (this region is above the ILE system to protect natural habitats, and it is unlikely that there would be any regions designated as ALCOR 5 in the UK).

The acronym ALCOR was selected because Alcor is the name of a faint star in the handle of the Plough, regarded as a test for good eyesight. Control of light pollution to appropriate standards for each ALCOR zone would expand what astronomers - amateurs and professionals, and the public at large - could see.

After extensive lobbying by the BAA-inspired Campaign for Dark Skies, the House of Commons Science and Technology Committee announced an inquiry into light pollution and UK astronomy in February 2003. The report is available on-line.

The Committee completely accepted the RAS's evidence on the significance of astronomy in the UK, both as first rate international research and as an inspiring cultural/educational activity to encourage students into science. It recommended that the Government should afford special protection to observatories, and local authorities be obliged to consult on planning applications in the vicinity of observatories. It suggested that PPARC should take a more active interest in light pollution issues than it has hitherto. It recommended that, "the Government should create a new Planning Policy Guidance on light pollution as soon as possible and ensure that all local authorities are made aware of their obligation to include lighting in their local development plans." They proposed that light could be made a 'statutory nuisance', like noise, fumes, smell, animals, and Environmental Health Officers exercise the same powers of judgement as they already do for smells. The Committee identified radio spectrum pollution as a matter of interest, although outside the scope of its present inquiry.

The report concluded that, "the astronomical community in this country is a particularly strong one and it should be encouraged by the Government. Amateur astronomers not only support major professional projects through day to day observations, but also donate much of their time to introducing the general public and young people to the night sky, astronomy and through that initial interest, very often into a physics career."


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