Wolverhampton Astronomical Society

Established 1951

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Window on Dark Skies

by Martyn Filsak

The past and the present

Just a few decades ago, a naked eye astronomer may have seen a couple of thousand stars in the night sky on a clear, moonless night. Now, from an urban location, the figure may be less than a hundred. The reason is sky glow caused by light pollution. Upward directed light is scattered by particles in the Earth’s atmosphere, causing a brightening of the sky which swamps the light from faint astronomical objects rendering them invisible. Stray light causes other problems as well: sideways light causes glare which produces an uncomfortable environment to drive in and can reduce visibility; stray light can adversely affect wildlife; all wasted light represents wasted energy, money (guess who ultimately pays), and large volumes of carbon dioxide.

The face of progress?

Is this just an unavoidable consequence of "progress" towards a technological society? Absolutely not! sky glow comes from lighting which is badly designed or wrongly installed, or quite possibly both. We have the technology to send light down to the ground, which, most of the time, is where it is needed, without spilling it upwards or sideways, but this technology is not always used. Some light will bounce off the ground and go upwards, but this is a tiny proportion of the incident light. sky glow could be greatly reduced by using good lighting, without reducing the amount of light on the ground where it is needed.

Why is there still a problem?

The reasons can be complex, but let me put it in these terms. Partly the problem seems to be of ignorance. Lighting users, whether organizations or individuals, are largely unaware of the sky glow problem, or if they are aware of it they do not necessarily know how simple the solution is. Another contributor to the problem is economic. Sometimes a cheap polluting light will be used in preference to a better quality one which may be more expensive.

Why campaign?

The response of astronomers to the problem of light pollution has been varied up till now, with maybe the vast majority of astronomers not taking an active role in campaigning for better lighting. Perhaps a major reason for the silence of many astronomers is a belief that nothing can be done about light pollution, and that we cannot make a difference. I think this is quite untrue, as demonstrated by campaigners in many parts of the country whose efforts have already resulted in darker skies for them. Perhaps the size of the task is daunting, and puts people off even starting since they feel that campaigning will take too much time and energy. In that case, let me commend the list of 15 ways to help the Campaign for Dark Skies. I am confident that each of us can find at least one point on that list to put into practice.

To join CfDS, please subscribe to the newsletter. Just send £2.40 (cheque payable to "British Astronomical Assn (CfDS)") for four issues to the British Astronomical Association at Burlington House, Piccadilly, London W1J 0DU. The newsletter is sent out every six months, so the subscription lasts for two years. I cannot think of any other publication which costs £1.20 per year!

The quality of the future night sky is in our hands! We can improve it for ourselves and future sky watchers. Watch this space for more coverage of dark sky issues, and please let me know of your campaigning experiences.