Posted by David Arditti at 02:46 on 2010 May 06
The answer is that the colour of sodium light is highly unpopular with the public. When consulted, people (non-astronomers) always demand white streetlights. They say it makes them feel more secure. This is behind the push towards white LEDs, as well as energy saving, and it is a highly political issue. I think it is very unlikely that astronomers will be able to bring pressure for non-white new lights to be introduced. Even Bob Mizon, when I asked him about it, expressed the belief that we cannot avert a move to white streetlights in towns, and the focus of the CfDS has been on getting the beam-pattern of lights improved rather than on their colour. Unfortunately, the greater upward reflectivity of white light off grass etc. is likely to more than compensate for improvements in beam patterns in terms of contribution to skyglow in the future.All round it is very bad prospect for astronomy and I often stress it at meetings as I don’t think amateurs realise what is coming. Here on the edge of London, where many of the lights in the centre of the city have already been changed to white, I can see the effect very clearly. If we could harness the support of the professional astronomical community more I think we would stand more chance of making an impact, but I think the trouble is, as they don’t generally observe from the UK, they don’t see it as such a big issue. They should all regard it, however, as part of their job to be working to preserve the sky that will inspire the next generation of both professional and amateur astronomers.