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.