Nearby exoplanets circle naked-eye-visible star

Re: unembuggered by light pollution.

I looked up into the London sky and saw a star through all the light pollution. A few of us checked a few astronomy references to try and identify it, and we're reasonably confident that it was Sol.

Re: denizens of city centres (who deserve what they get).

> The idea of a post-midnight switch off

Over on this side of the pond, they've just hacked down the light poles altogether, as it's a multiple whammy of saving electricity, pole/light maintenance costs, and anti-light-pollution.

So drivers have compensated by turning on their high-beams all the time, because we have tons of idiot forest rats deer randomly standing in the road. Sigh.

Re: denizens of city centres (who deserve what they get).

"The idea of a post-midnight switch off was briefly floated here before being roundly shouted down as irresponsible and dangerous by the local think-of-the-children brigade" -- AbelSoul

What? Which members of this brigade let their children out after midnight? Here in rural Warks, our lights go off at 00:00 (01:00 on Sat and Sun) and it's marvellous. In fact, the only downside is that I didn't know they were going to do it: first night it happened I went out with the dogs, stumbled over the lead of the electric lawnmower that I had, ahem, left out and, almost as I did so, all the lights in the village went out. Took me a second or two to work out what had happened ...

Re: Thank you

Sodium vapor gives the best LEDs a run for their money.

In terms of luminous efficiency that's correct now, but you the LED's are getting better, whereas gas discharge lamps are probably maxed out - a bit like CRT versus flat panel displays a few years back. It took about seven years for 100 lm/W LEDs to get from the manufacturers lab to commercial street lighting products, Cree had 300 lm/W in the lab eighteen months ago. Seems probable that by 2022 we could be seeing close to 300 lm/W in products you can buy. In domestic terms that means the equivalent of a 100W incandescent bulb would be consuming 5W, and a standard 60W equivalent a shade over 2.5W.

In terms of the environmental and economic benefits of your car park or street lights, you need to replace a sodium tube every three to four years, whereas the LED should last twenty years (fingers crossed). The main problem is that you can't just stick an LED "tube" in an existing fitting - you need a new luminaire (costing a couple of hundred even for the 20-30W units), and you normally need new control gear within the column (another couple of hundred). For a unit that only used 30W, for perhaps 4,000 hours a year, the economics are a real challenge. But even high performance sodium vapour aren't plug and play replacements - you usually need a new luminaire and sometimes new control gear, albeit the luminaire is often half the price of the LED.