The one saving grace of LEDs is that they can more easily be turned on instantly rather than having a warm-up period like many sodium street lamps. This opens the opportunity for many lamps to contain motion sensing equipment or otherwise be controlled by sensors located in buildings, roads, or other structures. The energy savings resulting from “in-use” lighting can be phenomenal, particularly in more rural environments (and it also multiplies the useful lifetime of your LED). It might be a bit disconcerting having lights flashing on and off all over the place but smart electronics could minimize the impact, or at least reduce the amount of flashing to acceptable values. Come to think of it there’s no need to turn the LED on or off abruptly either. The same activation circuits that control the lamps could also be used to gradually ramp lights on and off at a rate that’s more acceptable to the human nervous system, say over a span of 2 to 10 seconds or so, depending on the application.

I have an observing question: would it be practical for coastal astronomers to escape light pollution by setting up floating observatories offshore? I know this wouldn’t put them high in the atmosphere but it could take them far away from city lights. I don’t know how the problem of pitching and rolling would be solved unless the boat only went out in calm waters, but does the idea have any merit?

Thank you so much for you thoughtful response. South Africa is a beautiful nation. I had a dear friend for a while in graduate school from Cape Town and he shared some beautiful verbal and photographic images of your country with me. It is on my list of places I must eventually travel to.

If you were talking about Red or Orange LED’s, you’d be entirely right. With white LEDs… I have to admit that in you situation I really don’t know what is best. The problem is the blue (in the white light) scatters so much that it will cause a city to be a scattered light monster sitting on a horizon. All the pollution, haze, and everything else will scatter the light in all directions, and it also scatters more readily off the ground. The LED lights are better then completely unshielded lights, but they are worse than downward focused sodium vapor. But, even unshielded lights are better for our planet then burning coal.

It is always hard to balance the cost benefits to a society where such rapid development is going on. Small parts of your country are as developed as the cities I have lived in, but other (large) parts are still struggling with the basic needs of clean water.

I wish I had a perfect answer.

First off, thank you so very much for astronomy cast, it is wonderful to listen to up to date information and wonderful that there are still people like you who just want to share how wonderful the universe is. So many just don’t get it. I will need to pull out my old “Cosmos” vhs tapes and give them another listen to. I have kept them to show my children (one day when I have some) what science believed when I was younger. Should be quite interesting to see what’s changed and what hasn’t.

I live in Johannesburg in South Africa. That little blotch of light on the Southern portion of Africa more or less in line with Madagascar – thats us. Lucky me, I don’t have to travel too far to have dark skies and the viewing in winter away from the cities is generally very good with us being 1650m above sea level and very dry.

However even here the light pollution has grown exponentially over the last few years especially as the government has finally got its butt into gear and is trying to eradicate one of the vestiges of apartheid and electrifying the townships where unfortunately most folk still live mostly due to economic constraints rather than misguided political ones.

The double edged sword grows another edge as the number of poor that are using coal fired stoves has also decreased due to the electrification of squatter areas reducing particulate pollution even further, so one can hardly complain about it.

More to the point. LED’s generally have much lower viewing angles (the angle or cone that light is emitted) than for example a low pressure sodium bulb so, would this not reduce the amount of light that wasted, i.e. sent to far flung worlds instead of the car dealership?

In addition would the fact that the light has a higher frequency causing it to scatter more easily not mean that it is more likely to be confined to the city areas where there are lots of particulates in the air from gas and diesel combustion that will attenuate it and not pollute the outlying areas and higher atmospheric layers?

With this in mind would it not make sense for emerging economies such as ours to employ these new technologies as the light would hopefully be used more efficiently resulting in less fossil fuel power stations and less pollution to boot?

I was thinking that having a bright, low cost light source might even make cities and people want to save more money by not using as many of them, but your analogy with car dealerships shoots that down rather effectively.

Unfortunately, I also see that this may be even a worse situation since, with the energy costs of these lights being as low as they are, the power companies are going to encourage more of their use.

Bob Gent, the IDA President, who I have the good fortune of knowing, has never quite been able to effectively explain to me why power companies would go for lower lighting, although he does have specific and effective examples that this is the case. These lights may increase the need for that type of education.

Unfortunately, the only effective solution I see in this case is legislation, and that can be complex and expensive in terms of money and time since it tends to be an individual patchwork from community to community.

We’ll have to see how this begins to play out.