measuring light pollution - how new technology is making it possible
TRANSCRIPT
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]
Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.
This course is registered with AIA CES for continuing professional education. As such, it does not include
content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner ofhandling, using, distributing, or dealing in any material or product.
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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.
What is Light Pollution?
SkyglowGlareLight TrespassVisual Distraction
What is Light Pollution?
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
Measuring Light Pollution
Methodology Measurements from Earth’s surface - Night Sky Brightness Aerial measurements – Direct and reflected luminance Measurements from space (ISS and satellites)
Measuring Light Pollution
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
Measuring Light Pollution
Measuring Light Pollution
Measuring Light Pollution
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)
Measuring Light Pollution
Measuring Light Pollution
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
Measuring Light Pollution
Measuring Light Pollution
Measuring Light Pollution
Measuring Light Pollution
Measuring Light Pollution
Measuring Light Pollution
Measuring Light Pollution
Measuring Light Pollution
Measuring Light Pollution
Measuring Light Pollution
Measuring Light Pollution
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?
Can LED Fix Light Pollution?
5000K CCT 2200K CCT
Can LED Fix Light Pollution?
Amber LED
Can LED Fix Light Pollution?
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?
What do we have to lose?
What do we have to lose?
What do we have to lose?
What do we have to lose?
What do we have to lose?
What do we have to lose?
What do we have to lose?
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