Re: Light Pollution

Ted Forte

Blue light is the current problem in the lighting industry and it sort of snuck up on many dark sky advocates.

Here in my county, we entered the fray a half dozen years ago when the question of legalizing digital signs (Electronic Message Centers) was being considered. We fought hard to establish a CCT of 3000k as a standard and 2500k as a target. It mostly worked. It's at least in all the new codes. Enforcement is a different story, but at least the attempt is there.

Our major victory concerned the nighttime brightness of electronic signs. These signs are capable of producing a brightness of 10,000 NITS and we won concessions from the county where we got them limited to 200 NITS and the city of Sierra Vista where they are limited to 100 NITS ( a "Nit" being equal to 1 candela per square meter). Amazingly, the science shows that you need be only 30 nits brighter than the surroundings to appear "bright" to the human eye.

But the LED revolution has really ushered in a rush to bluer and bluer light. All is not lost though - properly designed fixtures can still mitigate the effect. We have a string of new street lights in front of our hospital and I would guess that if we measured, they would be too blue to pass muster, but they are no problem at all because of their full cutoff design. Approaching the sting of lights, you can't see the fixtures at all until you are right under them. The street is brightly lit, but there is no glare and no up-lighting. Very well done.


-----Original Message-----
From: <> On Behalf Of Bruce via
Sent: Monday, April 5, 2021 9:29 AM
Subject: Re: [BackBayAstro] Light Pollution

New LED installations appear to use daylight temperature colors in the 5,000 Kelvin range which are blue white to the human eye. Downtown Norfolk has replaced all it’s antique lamp posts with LED bulbs. All blue white, bright, and with no hoods! What night sky I had is gone and the glare is terrible.

Dr Bruce

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