Light Pollution and the City of Armagh
"It is indeed a feeble light that reaches us from the starry sky. But
what would human thought have achieved if we could not see the stars?"
Jean Perrin
1870-1942.
French physicist; Nobel prize for physics 1926.
What is Light Pollution?
Many of us have been dazzled at one time or another by an intense light
source, such as a stadium's floodlights or a neighbour's security light,
or struggled to see the wonders of the night sky through the now-familiar
yellow glow that accompanies any profusely illuminated area such as a car
park or shopping centre.
These are but some of the adverse effects of 'light pollution': the
inadvertent illumination of an area other than that which the given
light source is intended to cover. It comes in many forms:
light
trespass, for example when a neighbour's so-called security light
is shining into your garden or through your
bedroom window;
sky glow, the illumination of the atmosphere
by unshielded lights which limit our view of the cosmos to a handful
of the brightest stars; and
glare, the dazzling effect of
floodlights or spotlights which prevents one from making out objects
such as people or vehicles near the source.
Effects of Light Pollution
Night lighting is a necessary part of our lives. It enables people to
extend their activities after sunset and provides security for public
spaces and private dwellings alike.
Poor lighting, however, gives
rise to light pollution. This costs money by wasting energy; it creates
potential safety and security problems through glare, and it deprives us
of our view of the night sky.
Consider light waste. Lights are usually intended to illuminate specific
premises (a square, a building etc.). Improperly installed or shielded
lights emit a large portion of their energy away from the premises
(usually sideways or upwards) and thus waste money: hundreds of pounds per
unnecessary kilowatt, per year. Installing a
reflective 'skirt' around the fixture will redirect most of this wasted
light back towards its intended target, increasing the lamp's efficiency
and providing better illumination at no extra cost. Alternatively, a
properly shielded lamp of lower power can provide the same illumination
but with lower running costs.
Public safety and security at night require a certain amount of
illumination, and there is clear evidence that improved lighting
leads to cost-effective reductions in crime. However, rather than
increased surveillance and other deterrent effects, the benefits of
improved lighting are usually attributable to increased community pride
and confidence, both day-time and night-time crime decreasing together.
Bright lights help to allay the
fear of crime, but do little
to prevent crime itself; too much light is as much a problem as too little.
High-powered (300 - 1000 W) so-called 'security' lights not
only dazzle the eye but are extremely expensive to run, operating at much
greater powers than the
maximum (150 W) recommended for such
installations by the influential
Institution of Lighting Engineers.
Illustration of the sources and types of light pollution. A
well-shielded, well-directed light source (lower panel) goes a long way
towards eliminating sky glow, light trespass and glare.
Consider someone moving through your garden, or a moving flashlight beam
seen through an upper-floor window. The 'security' light impairs an
observer in several ways: (a) the glare reduces the chance that suspicious
movements will be detected, in part by turning shadows inky black; (b) it
gives the illusion of occupancy, so that neighbours or passers-by will not
be alarmed; and (c) it provides the perpetrator with a light source to
assist his activities. Glare from improperly directed lighting detracts
from security in the same way that a driver's ability to see the road
ahead is impaired by an oncoming car's headlights. The naked eye is an
amazing imaging and motion detection system. It should not be impaired by
shining excessive amounts of light at it.
Lost Views
Until now, every human being that has ever lived has enjoyed guaranteed
access to the observable Universe after dark, when stars, planets, and
galaxies are visible to challenge the mind and induce the rational
thinking that gave rise to civilization. Countless scientists and
engineers can trace the impetus of their careers in science and technology
to a fascination with the night sky during childhood. The sky is part of
humanity's cultural inheritance: a door to the Universe, part of the rural
environment, and a social amenity. The
sky glow of light
pollution reduces this vast celestial spectacle to a pale imitation - a
few pin-pricks of light - and robs us of a source of inspiration that
has operated for thousands of years and which until recently could be
taken for granted.
Dark-Sky Cities
Light pollution has been with us for most of the last century. In the
last decade or so, however, awareness of the problem has begun to take
off, as too have systematic attempts to mitigate it. Nowadays,
organizations are combating light pollution in virtually every
developed country around the world.
In the United States, for example, the
International Dark-Sky
Association (IDA) has been coordinating efforts since 1988 to lobby
and inform private citizens and local and federal government
departments on the benefits of good lighting practices, with great
success. A noteworthy example is the city of
Flagstaff, Arizona
(population 50,000), host to the historic
Lowell Observatory. As a
result of intensive efforts by the city council and private citizens
to pursue night-sky friendly lighting policies, Flagstaff was recently
awarded the title of the world's first Dark-Sky City.
Flagstaff is not alone. The City of Bisei, Japan, home of a major
national observatory and planetarium, recently passed a light
pollution ordinance to ensure compliance with the official policy to
preserve dark, star-lit skies. In order to reduce light pollution,
Bisei also provides subsidies of up to two-thirds of the costs of
installing, modifying or replacing offending light fittings.
Similarly, Spanish authorities have recently passed a law protecting
the night sky over the island of
La Palma, famous for its astronomical
observatory. In February 2002 the Czech Republic followed, and became
the first country to enact
national legislation to eliminate
light pollution. The
"Protection of the Atmosphere" Act took effect
on 1st June 2002.
Closer to home, the Campaign for Dark Skies, initiated in 1993 by the
British Astronomical Association (BAA), has raised UK awareness of the
problem, leading the Institution of Lighting Engineers to issue its
Guidance Notes for the Reduction of Light Pollution.
City of Armagh
The City of Armagh can perhaps be described as 'on the verge of
urbanization'. Light pollution is present, particularly in the vicinity of
recent developments, but it is still fairly localized. The position is
quite different in large cities, such as Belfast or Dublin, where the
problem has already acquired enormous proportions and is difficult (and
expensive) to mitigate. At the moment, Armagh and indeed many parts of
Ireland are exceptionally well placed compared to other parts of Europe.
The City of Armagh's southern skyline as viewed from the
Observatory in October 2002. Note the comfortable background of
well-dispersed medium-power sources. However, glare (and associated sky
glow) comes from a few poorly shielded light sources.
Click on image for larger version
Artificial night sky brightness over Ireland.
Bright colours show areas of greatest light pollution.
Courtesy of P. Cinzano, F. Falchi (University of Padova), & C.D. Elvidge (NOAA
National Geophysical Data Center, Boulder, Colorado), MNRAS, 328,
689-707, 2001. Reproduced by permission of the Royal Astronomical
Society.
Armagh - along with many similar-sized towns in Northern Ireland - is thus in
the happy position of being able to deal promptly and inexpensively with
isolated cases of poor lighting. Indeed, such a city can maintain this
situation by promoting good lighting practices, securing the view of the
night sky for future generations and maximising the advantage of having
low light pollution levels.
Armagh is also famous as the home of the
Armagh Observatory, the oldest
continuously functioning astronomical research institute in the UK and
Ireland, and the
Armagh Planetarium. In the eyes of its peers, it would
be natural for the City to secure continued access for its citizens to the
celestial spectacle that has played such an important role in its history
for more than 200 years.
Benefits
How can people living in towns and cities expect to benefit from
improved lighting practices aimed at eliminating light pollution?
'Right Light' policies will result in:
- Improved views of the starry sky, including the slow march of the
bright planets against the 'fixed' stars, the regular daily cycle and
seasonal advance of the constellations, and the monthly phases of the
Moon and its changing aspect through the year.
- More efficient - and hence lower cost - lighting of public areas
and private premises. This will save money and energy, and enhance public safety
and security.
- Avoidance of any unnatural biological, environmental or behavioural effects on
living plants and animals in brightly lit areas.
- Favourable publicity for the City and District, and a positive image
of Northern Ireland on the world stage. The City's involvement will
highlight its role in energy conservation and the reduction of waste,
and put the region firmly on the map so far as the environment is
concerned.
- Increased visitor numbers and tourism. Citizens of many countries,
particularly those in continental Europe, think very highly of such
schemes and would like to make a 'Dark-Sky City' part of their itinerary.
Summary
The development of a light pollution mitigation strategy will require a
census of lighting installations in the area and a systematic application
of proven guidelines. The overriding principle should be: "not too much;
not too little; but just 'Right Light' ".
Questions that should be asked of both existing and future installations
are the quality and amount of light, the need for it, and where it goes.
In short, what is its purpose, and how will it improve the environment?
Examining options to reduce stray light, one considers first the lamp's
shielding and directionality; secondly, its duty cycle; and thirdly,
opportunities to change the type of lamp or even the fixture.
Consider, for example, the case of a spherical or bowl-shaped lamp.
Reduced light pollution can be achieved by (i) painting the upper part of
the sphere black or installing a 'skirt' around the lamp, which if
reflective will increase the lighting efficiency for no extra cost; (ii)
turning the light off when it is not needed; and (iii) recessing the lamp
into its holder so as to reduce glare in the horizontal direction, or
replacing the entire fixture with a more directional lamp of lower power.
These options come at a variety of costs, but there is one to suit
every budget. Moreover, such work will only have to be done
once; future installations will be planned to comply with 'Right
Light' guidelines from the start. This is much more effective than
having to make later modifications.
In summary, good lighting practice benefits everybody. It conserves
energy, reduces cost, and increases public safety and security. The
development of 'Right Light' policies is an environmental issue which,
especially in areas such as Armagh, can be addressed simply and at minimal
cost. Elimination of light pollution will enhance the environment and
preserve our view of the wonders of the night sky - fully half our field of vision -
both for ourselves and future generations.
For more information, contact the authors.
Apostolos A. Christou, aac
arm.ac.uk
Mark E. Bailey, mebarm.ac.uk
Armagh Observatory
January 2003
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Last Revised: 2009 November 2nd
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