Seeing stars: light pollution

After last week’s exploration of the night sky with the BBC’s Stargazing Live team, it’s worth giving a thought to all those whose view of the solar system was spoilt by light pollution. Since the explosion of street lighting after the Second World War it’s been increasingly difficult to see stars against a dark sky – and I’m not talking about Professor Brian Cox.

According to The Campaign to Protect Rural England (CPRE), “In less than a decade, between 1993 and 2000, light pollution across England increased by around a quarter (24%). The amount of truly dark sky dropped from a sixth of the country to just over a tenth (11%). And seven per cent of our night sky – more than a twentieth – is now so light that people can see clearly.”

I’ve noticed this myself. Ten years ago, my own night-time view towards the South Down’s was virtually black; now there’s a constant winking of security lights and some of the scattered buildings seem permanently to be illuminated. And it’s not only the light pollution that’s disturbing, it’s the huge and unnecessary waste of energy.

Obviously we need light; we can no longer rely on ‘the parish lantern’ (the moon) as our ancestors did. One of the problems is that the light is often blasted in the wrong place at the wrong time.

There are things we can and should do. Once it’s been established that a light is really necessary, it’s vital to choose the fitment carefully. Fittings that shine light into the sky should be avoided. When installed, they must be positioned so they illuminate what they’re meant to and as little else as possible. If necessary ‘spill’ from security lights can be controlled by a carefully angled metal sheet fixed alongside.

Passive infrared (PIR) motion detectors will help minimise the time that lights are lit, cutting both light pollution and energy use. For the same reasons, choose energy efficient fittings and the minimum brightness lamp necessary to achieve the required level of illumination. Floodlighting of buildings needs to be treated particularly sensitively and thought given to whether it’s really necessary. Where it is installed, it’s best linked to time switches that are set to avoid over use.

The other consideration is the building itself. Think carefully about the aesthetic impact the lamp will have and the damage that fixing it and any cable will cause. One way of minimising the impact of cables is to use self-contained solar powered lamps; these also offer the added advantage of generally having a lower light output.