Measuring Light Pollution - How New Technology is Making it Possible

Light PollutionWhat is it, how do we measure it, and how do we fix it?

Bob Parks, MIES, LCExecutive Director

Smart Outdoor Lighting Alliance (SOLA)[email protected]

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Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

Twenty five years after the term “light pollution” was coined, we still have a hard time understanding what it is. Measuring it is difficult and metrics to describe it are still being developed. Innovative techniques like all-sky imaging and aerial photography are finally making it possible to accurately measure night sky brightness. International Space Station and satellite imagery is also being used to measure global sky brightness and document trends in its proliferation. This session will demonstrate how to measure different aspects of light pollution and examine the metrics that have been developed to quantify it.

What is Light Pollution?

*Define what light pollution is and how it can be measured. *Learn what metrics have been developed to quantify light pollution.*Demonstrate the tools and technology being used to measure night sky brightness.*Understand how new LED lighting technology may help to reduce it in the future.


SkyglowGlareLight TrespassVisual Distraction


Skyglow

Skyglow

Most recognizable light pollution feature by public

Impacts astronomy, ecology and karma Produced by the scatter of light interacting with

moisture and particulate in the atmosphere Light +/- 10 degrees of horizon causes most Uplight and reflected light contribute Different wavelength light behaves differently

Skyglow

Different wavelength light scatters differently Mie scattering defines light scatter in aerosols

Primarily responsible for “local” skyglow Wavelength agnostic Redirects light through moisture in all directions

Rayleigh scattering defines scatter through molecules Shorter wavelength scatters more Is what makes the sky blue, sunsets red Characterizes skyglow visible at great distances

Skyglow

Broad Spectrum White Light (LED) Contains significant quantity short wavelength, blue SPD Higher the CCT, the more blue SPD Scatters 3-5 times more than longer wavelength If installed at same intensity as HPS, skyglow is 3-5x greater White LED starts as blue, white light is created by converting

blue SPD centered at ~460nm with phosphor The blue 460nm peak corresponds with the circadian

detector cells in every species.

Skyglow

Skyglow

Skyglow

Glare

Glare

Glare

Caused by light directed into eyes, not target area IES defines light range of 60 – 90 degrees of nadir Defined as “nuisance” or “disability” Dramatically degrades visibility Requires increased lighting levels to compensate Often the byproduct of “enhanced” uniformity Product of poor lighting design Disproportionately impacts seniors due to the physiology of the aging eye

Glare

Light Trespass

Light Trespass

Light Trespass

Created by light directed onto adjacent properties Caused by poor design, ignorance and insensitivity Most common public complaint to authorities Disturbs quality of life and karma Subject of frequent lawsuits and violence Property rights vs. “quiet enjoyment” Byproduct of poorly installed “security” lighting Local DOTs responsible for most light trespass #1 reason for development of most lighting ordinances

Light Trespass

Visual Distraction

Visual Distraction

Visual Distraction

Measuring Light Pollution

Methodology Metrics Tools and technology


Methodology Measurements from Earth’s surface - Night Sky Brightness Aerial measurements – Direct and reflected luminance Measurements from space (ISS and satellites)


Metrics Bortle Scale – Night Sky Brightness

Uses limiting magnitude of stars for comparison or photometer measurements

Measurements can be made visually Uses zenith measurements (normally darkest) Scale of 1 to 9 is not very intuitive (9 is worst) Doesn’t account for skyglow at horizon




Metrics Sky Quality Index (Developed by NPS) – Night Sky Brightness

Uses calibrated photometer and star “plate-solving” Extremely accurate Starts by calculating “natural sky” as a basis Then calculates the anthropogenic (man-made) portion Measures the entire sky with 26 separate images Samples are weighted based on location in sky Scale of 0 – 100 is easy to understand (0=Bad/100=Good)



Tools and technology Photometers

Range in cost from free to very expensive Accuracy and repeatability increase with cost Typically measure a very small portion of the sky Measurement of luminance in candela per meter squared

(cd/m2) Astronomical CCD and DSLR Cameras

Need to be calibrated as a system (camera + lens) Can capture entire sky in single image with fisheye lens Uses computer to create luminance calibrated color map












Potential advantages of LED Superior distribution of light possible White light can provide same visibility with less lumens SPD of LED can be designed to reduce glare, skyglow and

ecological impact on plants, animals and humans Adaptive controls can dim and change SPD dynamically Amber LED can replace LPS near observatories

Can LED Fix Light Pollution?


5000K CCT 2200K CCT


Amber LED


Dynamically SPD Tuned LED (EXO Optics)

Does the public care enough to curb light pollution? Historically every increase in efficacy has resulted in more

lumens, not energy saving Will energy costs and climate change effect our trajectory? Public equates lighting with enhanced safety Primal fear of the dark has beat out the night sky and

environment for the last hundred years Only 20% of public have ever seen a natural night sky Who will miss something that they didn’t know existed?

Will LED Fix Light Pollution?

What do we have to lose?









Light PollutionThank You.Questions?

Bob Parks, MIES, LCExecutive Director

Smart Outdoor Lighting Alliance (SOLA)[email protected]

This concludes The American Institute of ArchitectsContinuing Education Systems Course