Measuring Light Pollution - How New Technology is Making it Possible.

Editor's Notes

• #3  Light Pollution What is it, how do we measure it, and how do we fix it?
• #5 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 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.
• #6 *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.
• #7  Skyglow Glare Light Trespass Visual Distraction
• #8 A town on the Florida panhandle from a distance.
• #9 And up close and personal.
• #10 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
• #11 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
• #12 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.
• #13  Broad Spectrum White Light (LED) Here’s a range of various light SPD with the circadian curve in the upper left. Notice that both the circadian and LED peaks are in the 460-480nm region.
• #14  Broad Spectrum White Light (LED) Here’s the circadian and LED peaks in another graph.
• #15 Montreal at night but could be any major city. This image by Jim Richardson is from a National Geographic article.
• #16 I’m not lovin’ this.
• #17 This is security?
• #18 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
• #19 Is this really what we should be seeing when we look out our windows at night?
• #20 An image from Ian Cheney’s “The City Dark documentary on the impact of light pollution on society. It bares a strong resemblance to what I’ll see from my hotel room tonight.
• #21 Brooklyn after being retrofitted to LED. Is this really the best that we can do?
• #22 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 Subjects 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
• #23 Visual distraction taken to its logical conclusion. Tokyo is the worst, but NYC really vies for the title.
• #26 This is what you’d see if you were a satellite. This is a composite made from the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi NPP weather satellite
• #27  Methodology Metrics Tools and Technology
• #28  Methodology Measurements from Earth’s Surface Aerial Measurements Measurements from Space
• #29 Metrics Bortle Scale – Night Sky Brightness Uses Limiting Magnitude of stars 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
• #30 A comparison of different metrics used to quantify night sky brightness.
• #31 A false color map of the Northeast using the Bortle Scale.
• #32 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)
• #34  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 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
• #35 Available tools for measuring night sky brightness include: The free “Dark Sky App” on left. The Unihedron Sky Quality Meter or SQM in the middle And a DSLR with Fisheye lens on the right
• #36 The National Park Service’s computer controlled CCD All-Sky Imaging System in the field. It takes 26 separate images and stiches them together into an all sky image. It compares know luminances of stars to calculate very precise night sky brightness.
• #37 An example of the NPS all-sky measurement system using false color.
• #38 An example of an original all-sky image taken with a DSLR and fisheye lens on left. And the false color, luminance calibrated image on the right. These were taken to document light pollution at Lackland Air Force Base near San Antonio Texas.
• #39 An example of a very high resolution aerial image of Leicester the UK using the UltraCam by a company called BlueSky. The airplane flies at about 10,000 feet. Allows for easy identification of sources of light pollution and the type of lighting being used.
• #40 The Microsoft UltraCam designed for aerial imaging. Currently state of the art for aerial imaging at night.
• #41 Paris from Space
• #42 Athens
• #43 Guess where…
• #44 Astronaut Don Pettit operates a low tech “barn door” tracking device powered by a Makita cordless drill on the ISS. It uses a DSLR camera and fast telephoto lens.
• #45 Can LED Fix 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 Low Pressure Sodium near observatories
• #46 Here’s the Spectral Power Density of 5000K CCT on the left and 2200K CCT on the right.
• #47 This is the spectral power density of true amber LED.
• #48 Hubbell offers a line of LED with Zero SPD below 390nm that can be dynamically tuned to become eco-friendly during most of the night.
• #49 Will LED Fix Light Pollution? 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?
• #53 Light pollution disorients and kills thousands of baby sea turtles each year, causing them to craw towards the brightest lighting on the horizon. This is often the lights from development and they never make it to the water.
• #54 Millions of birds die each year from collisions with lighted buildings and communication towers. Skyglow and bright lighting also attracts migratory birds which become captured and unable to return to their migration. They use precious energy, become exhausted and die.
• #55 Amphibians are in steep decline and artificial light at night is a major cause. Frogs stop making mating calls when lighting levels are high at night.
• #56 Bats, already under extreme decline from White Nose Syndrome travel farther to forage and this results in lower body weights for females and less offspring.
• #57 Invertibrates die by the billions each year due to their attraction to light. While not as cute as other species, they are a vital link in the food chain of many others like birds and bats.
• #58 Fireflies communicate by light and cannot mate in light polluted areas. While commonplace a few decades ago, they have all but disappeared in most urban areas.
• #59 Thank You Questions?