The Boston Globe reported on July 26 that Gloucester has been awarded $240,000.00 to convert streetlights to LEDs; the move is reportedly expected to save the city $130,000.00 annually on its electric bill. This is great news, but only if we’re careful with the type of LEDs that we wind up with.LEDs are by nature rich in blue light. And shining blue light around at night is a terrible idea.The sky is blue in the daytime because blue light from the sun is scattered in the atmosphere most easily. This is, unfortunately, also true at night — the blue light component of streetlights is scattered in the atmosphere and produces sky glow, which blocks out the stars and causes glare. Glare is bad for drivers, and for birds and other living things that need the dark, and for other natural resources, including the night-time sky.
The more blue light, the fewer stars we can see. We could easily lose one of Cape Ann’s great tourist attractions, our rich night skies, in the transition to the wrong LEDs. Most folks never get to see the Milky Way, but we see it all the time; tourists are often quite surprised at the beauty of our night skies. But once the stars are gone, they’re gone. Go to Boston, for example, and look up.
The good news is that in addition to saving money, we can have more environmentally-friendly lighting by being smart about our choice of LEDs. Here’s how: the amount of blue light produced by streetlights is measured by color temperature. 4000k lighting has a lot of blue light mixed in; this is obvious to the eye. 3000k lighting or lower produces a warmer color and is not just more pleasing to the eye, but better for you, for nocturnal wildlife, and much better for our night time skies.
We encourage readers of GMG to write or call the folks who will be involved in choosing our new LED streetlights, and to ask them to choose lower glare, healthier, and more night-sky friendly 3000k lights over blue-light rich 4000k lighting.
The undersigned GAAC members, active astronomers in the area, sprinkled all over the North Shore and beyond, consider Cape Ann as the best viewing in New England. At least once a month we drag our telescopes, large and small, to the north east corner of Cape Ann for the incredible dark sky that we have here. GAAC shows the night sky to hundreds and hundreds of folks from here and away every year, and we’ve seen the night sky disappear in too many other locations. Let’s not let this happen to Cape Ann.