Presteigne Dark Skies

Logo: Presteigne Dark Skies

By Leigh Harling-Bowen Presteigne and Norton Community Dark Skies Leader

Background to the Dark Skies Movement

Long exposure of a car driving down a dark road
Norton ( Leigh Harling-Bowen)

Since the early part of this century light pollution has been increasing, especially in the Western Europe and North America. Latterly, this has been followed by Developing Countries as they try to emulate the West.

Streetlight luminaires were primarily high pressure sodium, which gave an orange glow and mercury emission (or metal halide), which gave a blue-white light. Both types of streetlight were expensive to install, run and replace. In addition dead mercury luminaires were classed as hazardous waste and their disposal was problematic and expensive.

Enter the light emitting diode (LED). Although LEDs themselves were invented by electrical engineer Nick Holonyack, Jr. in 1962, the first LED street lights were not installed in the UK until 2011 in Somerset. Since then the technology has boomed and local authorities, businesses and contractors are continuing to utilise it to maximise energy and cost savings. LED street lights operate at a fraction of the cost of sodium or mercury lights. Indeed, local authorities found they could almost install and run two LED street lights for the price of one sodium lamp. The installation of cheap LED street lights then started to proliferate.

Most light emitting diodes operate by emitting ultra-violet light, which is then converted to visible light by the use of a chemical phosphor in the lens. The choice of chemical phosphor determines the colour of the light emitted. First generation LED street lights emitted a blue-white light with a wavelength range of 400-500 nanometres and a colour temperature of 4,000-6,000oK. Although these lights were cheap to manufacture, a negative side effect was that they produced a lot of glare and light pollution, giving “sky-glow”. This effect has been found to have a negative impact on the environment, wildlife and human health.

The introduction of dark skies compliant street lights that have a colour temperature of less than 2,700oK can help to address this, as the warmer colours do not produce as much glare and subsequent light pollution.

The Cost of Lighting up the Night Sky

Astronomy and Environmental Management may seem strange bedfellows, but this is how Presteigne Dark Skies first emerged.

As an amateur astronomer I was a member of Marches Astronomy Group, which met at the Spaceguard Centre near Knighton in Powys. The Spaceguard Centre is a working observatory and the ‘National Near Earth Objects Information Centre’, which tracks Earth grazing asteroids and comets, looking out for “the big one” that has our name on it!

Look out over a night landscape with the sky lit up by a nearby town
Light pollution from Spaceguard (Spaceguard Centre)

Looking to the South of the observatory, I was well aware of the visible light pollution coming from the small town of Presteigne. This light pollution was interfering with the Centre’s observations.

At the same time I was employed as ‘Environmental Coordinator’ with Powys County Council and tasked with implementing and managing the Councils ‘Green Dragon’ Environmental Management System. At the time Powys had Green Dragon level 5, which was the highest level of Environmental Accreditation of any local authority in Wales. Green Dragon level 5 was equivalent to the European Eco-management and Audit Scheme (EMAS) and as such the Council was required to write an annual environmental report that documented its environmental aspects and their impact. Through this report it emerged that street-lighting had a significant environmental impact in terms of energy, greenhouse gas emissions and the subsequent effect on wildlife.

There are around 7.5 million street lights in the UK and they typically waste 15-20% of their light illuminating the night sky.

The total cost of light wasted in the UK by street, domestic and commercial lighting exceeds £1 billion a year; some estimates put it at £3-5 billion.

Over 800,000 tonnes of CO2 are produced in wasted energy per year. This is equivalent to 300,000-500,000 tonnes of coal. That’s about half the coal used in the energy output from a 500MW coal fired power station, just to light up the night sky!


Light pollution affects bird, bat and insect populations.

Generally, birds migrate at night, navigating by the stars. Light pollution from towns and cities confuses them, can send them off course and in extreme circumstances collide with brightly lit tower blocks in cities. Feeding and mating behaviour is governed by day length and light pollution can put stress on bird populations by inducing this behaviour early.

Mid Wales is the last stronghold of the lesser horseshoe bat, (Rhinolophus hipposideros). In some parts of England it is virtually extinct. This bat is a late emerging species, emerging at around midnight. It is particularly sensitive to light pollution from street lights, actively avoiding them when foraging. This puts stress on the species but also it is thought that, as a small and fairly slow flying bat, being illuminated makes them vulnerable to predators such as owls and raptors.

Building in a town surrounded by bright cold white lights
Assembly Rooms before (Kerem Asfuroglu)

Insects are at the base of a giant food web we all indirectly rely on. Night flying insects orientate themselves by the stars and the moon. Bright lights confuse them and they end up spiralling around the light and eventually die from exhaustion or get predated by birds and some bat species. It is thought that the current crash in insect numbers can be attributed in part to light pollution.

How Presteigne Dark Skies tackled these issues

The first step was to contact the Commission for Dark Skies, who look after ‘dark skies’ stuff in the UK. They put me in touch with Kerem Asfuroglu, a genius lighting designer from Dark Source an environmentally sustainable lighting design practice. Kerem was recently awarded a National lighting design award, for designing the lighting in Eryri National Park, a dark sky reserve.

Kerem taught me more than I really wanted to know about streetlights, and we came up with a cunning plan to take to Presteigne and Norton Town Council, where we would lobby for dark sky compliant street lights and become a dark sky community. The Town Council quickly came on board and in turn we presented a case to Powys County Council. Things went quiet for a while and then we heard that Powys had been given grant funding to progressively replace the street lights, starting with Presteigne!

Because we had measured the amount of light pollution with a sky quality meter before the lights were changed, we could easily see the improvement when the new lights were put in and this helped when we applied for dark sky status.

In January 2024 the community of Presteigne and Norton were awarded International Dark Sky Community Status, the first town in Wales and England!

The same building in a town now lit with gentler warm lighting
Assembly Rooms after (Leigh Harling-Bowen)

The Environmental Benefits

Because the new lights use about half the energy as the old lights and we reduce the light intensity by 50% after midnight, the following savings have been made:

  • An energy saving of nearly 20,000 kW per year;
  • A cost saving of over £8,200 per year.
  • A saving in greenhouse gas emissions of over 4.5 tonne CO2 e/year.

Presteigne & Norton is a small community of around 2,700 people; imagine the benefits if this were rolled out on a larger scale!

To Sum Up

Reducing light pollution through Dark Skies:

  • Enables us to see the glory of the night sky clearly and helps professional astronomers do their job.
  • Reduces our impact on the environment by the use of efficient low energy ‘dark skies’ street lights.
  • Has a beneficial effect on wildlife, especially night flying insects, birds and bats.


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Posted On: 29/03/2024

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