LED streetlamp aims to improve public's view of stars

Lighting engineer discussing this: <a href="http://www.reddit.com/r/science/comments/1d3hd1/researchers_believe_they_have_come_up_with_a_new/c9mn785" rel="nofollow">http://www.reddit.com/r/science/comments/1d3hd1/researchers_...</a>

There's another issue not covered by the article, apart from the degree to which the light's emission angles are controlled, and that is spectral lines. Many conventional streetlight designs emit their light along narrow spectral lines, a trait resulting from their gas-discharge design, and those spectral lines prevent spectroscopy (a large part of modern astronomy) from being carried out as it should.<p>LED lights don't have narrow spectral lines, so they represent an advantage for this reason also.

I'm not so sure that all of the claims are true (or maybe just not well-explained) in that there exist "full cutoff" lights that don't direct light upward. The researchers' light may indeed be an improvement, but it was not made clear to me what it would be over existing full cutoff lights. Based on the illustration, maybe it has more to do with the light not scattering all over the place and therefore not reflecting off objects as much.<p>It also seems to be an awful lot of "on paper" considering they haven't built a prototype.<p>Finally, as I was searching for "full cutoff" to make sure I wasn't imagining it, I found this informative website on the subject of light pollution and solutions: <a href="http://www.lrc.rpi.edu/programs/NLPIP/lightingAnswers/lightPollution/indicatorDirectUplight.asp" rel="nofollow">http://www.lrc.rpi.edu/programs/NLPIP/lightingAnswers/lightP...</a>

I find this story quite strange because there are LED street lights right outside my front door here in Oakland. They went in last year, and it was a bit weird the first time I saw them turned on because the light looked very cold, almost blue compared to the lights that were there previously.

Are street lights the biggest contributor to light pollution?

Surprised sidewalks aren't mentioned. The "perfect" design shows that the they would need separate lights.