25 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 high dynamic range photography are finally making it possible to accurately measure night sky brightness and glare. 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. Presented by: Bob Parks Smart Outdoor Lighting Alliance

2. What is it, how do we measure it, and how do we fix it?
Bob Parks, MIES, LC
Executive Director
Smart Outdoor Lighting Alliance (SOLA)
bparks@sola.lighting

3. 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 of
handling, using, distributing, or dealing in any
material or product.
___________________________________________
Questions related to specific materials, methods, and services will
be addressed at the conclusion of this presentation.

4. 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.

5. *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.

6. Skyglow
Glare
Light Trespass
Visual Distraction

9.  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

10.  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

11.  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.

17.  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

21.  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

26.  Methodology
 Metrics
 Tools and technology

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

28.  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

31.  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)

33.  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

44.  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

45. 5000K CCT 2200K CCT

46. Amber LED

47. Dynamically SPD Tuned
LED (EXO Optics)

48.  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?

58. Thank You.
Questions?
Bob Parks, MIES, LC
Executive Director
Smart Outdoor Lighting Alliance (SOLA)
bparks@sola.lighting

59. This concludes The American Institute of Architects
Continuing Education Systems Course