Save the Night | Be the Solution, Stop Light Pollution
Save the Night | Be the Solution, Stop Light Pollution
A streetlight or other outdoor fixture sends out light in many directions, but in essence it all goes into one of three zones:
Uplight is any light that shines above horizontal; virtually all of it goes straight into the air, uselessly, and is a direct cause of skyglow.
In the glare zone, light leaves the fixture below horizontal but at a highly oblique angle that can be seen directly by drivers or pedestrians. This creates glare that’s either discomforting or even disabling to our eyes. Glary fixtures are actually a safety hazard.
Useful light illuminates the ground without causing uplight or glare. This is a hallmark of well-designed light fixtures. A small fraction of useful light is reflected off the ground and up into the atmosphere.
There are 199 decorative streetlamps on the island, primarily in the downtown historic area and in 'Sconset. These are owned by the Town and National Grid helps maintain them.
All but a few of them are High Pressure Sodium (HPS) fixtures. The LED fixtures that have been installed are either 3000K, 2700K or 2200K.
Source: The Town of Nantucket's Energy Office in consultation with National Grid.
The island has 593 "cobra"-style streeltights (the ones on utility poles). These are currently owned by National Grid. Most of them are still High Pressure Sodium (HPS) but some are LED, including six on Milestone Rd that are 4000K. These were installed in 2019-20 as part of a pilot to gauge community reaction. (More on that below.)
Source: The Town of Nantucket's Energy Office in consultation with National Grid.
The streetlights and streetlamps that illuminate the streets of Nantucket have become both old and outdated. A great many other communities in Massachusetts (and around the country) have already converted their streetlights to new ones powered by light-emitting diodes, or LEDs. And the time has come to consider such a conversion for Nantucket.
LEDs offer great advantages in terms of energy savings and reduced electricity costs. However, if chosen poorly, they also have the potential to greatly increase the amount of glare that drivers, pedestrians, and those with homes near streetlights must cope with, as well as increase the light pollution in our naturally dark nighttime skies, reducing our ability to see the stars at night and causing harm to wildlife (see article below).
Lovers of Nantucket's dark sky need to pay attention and monitor developments on this front to make sure the right choices are made!
WPI STUDENT REPORT:
Investigating the Conversion to LED Streetlighting on Nantucket (Dec. 2021)
LED STREETLIGHT CONVERSION FEASIBILITY AND COST-SAVINGS STUDY (2022):
CHECKLIST
IDA-MA Checklist for Dark-Sky Compliant Streetlights (August 2022)
In 2019-20, six of the "cobra"-style streetlights on Milestone Road, owned by National Grid, were converted to LED at the Town's request to gauge community reaction. The blue teardrops on the map above show their locations. The fixtures are 4000K and 48W.
While these LEDs are more energy efficient and more dark-sky friendly in some respects than the HPS streetlights they replaced, their color temperature is higher than that recommended by the International Dark Sky Association and the Massachusetts Medical Society. DarkSky International (formerly known as the International Dark Sky Association) now recommends 2200K for "most" outdoor lighting applications, and the Massachusetts Medical Society recommends no higher than 2700K.
At the time of installation, National Grid's policy was to install only 4000K LED for streetlights that they own. While they now offer 3000K, the fixtures they have chosen to purchase are reportedly not ideal in terms of backlighting, uplighting and glare. To have better fixtures -- and the option of having streetlights lower than 3000K -- the Town would have to purchase the streetlights from National Grid and assume responsibility for converting them to LED and then maintaining them, as many other towns have done. (A preliminary analysis by a streetlight consultant indicates that this would SAVE the Town money in the long run.)
Please see below about the "promise and pitfalls" of LED streetlighting and then, if you would like to provide feedback about the LEDs on Milestone, please email Nantucket's Energy Coordinator, Lauren Sinatra, at
LSinatra@nantucket-ma.gov (with a cc to us at nantucketlights@gmail.com).
As published in Sky & Telescope Magazine, May 2015. Reprinted with permission.
NOTE:
This article refers to a recommendation by the International Dark Sky Association -- now known as DarkSky International -- to use outdoor lighting that is no more than 3000K in color temperature. In 2021, the IDA changed its recommendation and now recommends 2200K for "most" outdoor lighting installations.
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