Thursday, May 21, 2009

New Streetlights in Carlsbad

The City of Carlsbad is moving closer to switching out their existing high-pressure sodium streetlights in favor of white induction lights. The San Diego Union Tribune reported here on it last week. It even got a mention in the Carlbadistan blog. A few days ago I posted here about why astronomers love low-pressure sodium lights and how white light can pose problems for the observatory.

Last Saturday night I got the chance to go out and see the new lights that are being considered.

Here are some of the acorn lights being tried out along Carlsbad Village Drive:

Pretty much all Acorn lights are not dark-sky friendly. You can see that their light shines in all directions. It is a small percentage of their light that actually goes downward where people are. Note the light shining upwards on the palm tree. Of course these lights are more decorative than functional. Carlsbad isn't unique in using them. They are quite popular and can be fitted with internal shields which will keep their look the same in the daytime, but direct the light downward at night.

The unique shape of the acorn light makes for an usual looking spectrum.

If my memory is correct, below is a LED streetlight along State Street:

The City has decided not to pursue using LEDs. Maybe that is a good thing. Notice that there is plenty of light that is completely missing the target by shining on the building and trees and not downward to the street.

This is an induction light along State Street:

And some of the existing high-pressure sodium lights:

Which lights are brighter? These last two photos were taken with exactly the same camera settings.

The City has decided to move forward on the plan. Here's a story on it from the San Diego Union Tribune summarizing the plan and the action taken by the City Council Tuesday night. I will be working with City officials to see if we can find the best solution for Carlsbad and Palomar.


Anonymous said...

Agreed, the city should have used fixtures that point the light downward where it is needed but the white light is definitely more pleasing to the eye.

jg said...

If it helps to persuade Carlsbad, you can show them these guidelines:

Design Guidelines for Redevelopment Project AreaThey were developed by the economic development agency of Riverside for a project area I live in. Around page 10, it mentions the goal of preserving the night sky through use of LPS lights in restored historic acorn style lamps.

At the time we created these guidelines (I'm on the committee, still), our architect reported finding a limited number of manufacturers of acorn lights with LPS bulbs, and that internal shielding was impossible with LPS, because the LPS bulb had to be longer than other bulb types. I wonder if this is still true. So the choice was unaimed LPS or aimed, clear-glass HPS.


Parcus said...

I would like to point out that there are different LED technologies that would have made a big difference. LED produce a more pleasant colored light with much better contrast than the High pressure Sodium (HPS). The picture proves that, yet the luminary used did a very poor job in properly directing the light. Having a HPS in the same fixture would have given the same result. For full disclosure I am a distributor for LED Street lamps and other LED luminaries. I believe that shortly all cities will turn to LED because they are overall friendlier for the environment and save the cities much on maintenance and operation cost.

Dilapidus said...

Parcus.. I think the purpose of HPS is to provide light in a very narrow wavelength so that the Observatory can easily filter it out from their observations. I'm pretty sure those LEDs are putting out very broad spectrum light and helping render a jewel of an observatory useless.

Anonymous said...

Santee announced today that they are switching out old mercury vapor lights for induction lights. Could I get an official comment from someone about whether this would interfere with Palomar observatory or any other astronomy viewing areas in the area? email with comments, title, and affiliation please. Thanks.

Anonymous said...

My Carlsbad neighborhood street lights just got switched out with the new lights and it looks terrible! They are very bright, and you cannot see the stars well at all! The light penetrates closed blinds, and it is not "pleasing to the eye" by any stretch. It's too bad we have to give up what little of nature we could enjoy. Stargazing at home...not anymore!