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Combatting Light Pollution: Preserving Our Dark Skies

Light pollution is a growing concern that obscures our view of the night sky and disrupts ecosystems. This primer explores the sources and impacts of light pollution, particularly in the context of the Blue Ridge Mountains, where our Dark Sky Observatory is located. With a $1M investment in infrastructure, we've created a hub for astronomers and hobbyists to combat sky glow from poor fixture design and over-lighting. Learn how to protect our astronomy heritage and make informed choices about outdoor lighting to preserve the beauty of our night skies.

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Combatting Light Pollution: Preserving Our Dark Skies

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  1. Light Pollution: a Primer Dan Caton and Lee Hawkins

  2. Lighting: Opposite of Imaging What we do What you do

  3. My Concern: our Dark Sky Observatory • In the Blue Ridge Mountains of western North Carolina

  4. 32-inch Telescope • Lab for four astronomers and their students • $1M investment

  5. Dome and Cline Visitor Center

  6. 100,000 hobbyists

  7. Everyman…

  8. Just as important

  9. The basic problem: Sky Glow • Light from fixtures reflects off particles in the sky—”Sky Glow.” • Large cities visible from tens of miles. • The stars are not brighter here in the country …

  10. …The sky is darker!

  11. Global Problem

  12. Light “Made in the USA”

  13. What’s Wrong With this Picture?

  14. Closer to home You are here!

  15. Boone, 40 years ago…

  16. … more recently

  17. Even at Kitt Peak

  18. Charlotte… Courtesy Spencer Rackley, III

  19. Where does the sky glow come from? • Poor fixture design • Lack of shielding • Over-lighting • Poor installation • Market pressure

  20. Floodlights • Almost horizontal • No shielding • At night …

  21. Here at the Ramada

  22. Last night

  23. Floodlight used in ATMs • Glare! Could you see a criminal? … • He can see you…

  24. Better: Full Cut Off (FCO) • “Shoebox” design • Why do you think they are chosen? … • Appearance in the daytime! • At night …

  25. Burger King, Tucson In Boone…

  26. New Advance Auto, Boone

  27. Even Better! • Van Gogh’s Café Terrace at Night,1888 • Experience at Tweetsie. • Result from California study: reduce glare and you can reduce the overall lighting level

  28. Sidewalk Lighting • Post-top fixtures like these on ASU campus are often very glaring… • ASU has now adopted the Night Sky optics option

  29. Acorns

  30. Residential Post Mounts • Not many FCO fixtures available • This unit by Minka • I recommended this to Cielo Falls, a development of ~250 “cabins” (>$850k), near our Observatory

  31. More options!

  32. Residential Entry • Ditto: not many FCO fixtures available • This unit also by Minka • Soffit lights better—also do not draw bugs

  33. Billboards: the Bad Way • Uplighted • Most light reflected into the sky • Often on all night

  34. Roadway lighting: overhead glare

  35. Cobra heads • Filament below reflector • Glaring to driver • Light polluting

  36. Better, FCO Fixtures • No light above horizon • Non-glaring to drivers, too! • May require more poles per mile • At night …

  37. “Security” Lighting • “Dusk-to-dawn” • Security or lighthouse? • Refractor very glaring and light polluting • Frequent light trespass and neighbor problem • Installed by amateurs and utilities

  38. The Glare at Night (From High, Too!)

  39. Solution: Sky Cap • GE SkyGard shown • Hubbell available • Total FCO • See results …

  40. The Capped Light at Night

  41. The Data

  42. Private Security Lights

  43. Health concerns • Baby sea turtles attracted to street light • Cancer and melatonin production in people

  44. This “1973” shot impossible today! “Space Jam”

  45. Car Sales Lots • Often grossly overlit • This one at 60-110 footcandles on lot, 65 on road • Use astronomically unfriendly metal halides • Can use sodium with 10% white to get color rendition

  46. … like this (Tampa)

  47. Wall Packs • One of the worst fixtures for pollution as well as glare • Are available in FCO • What is the point of these? 

  48. Sports Lighting • Usually done poorly with lots of light pollution and light trespass. • Can be done well as shown here, using fixtures like ….

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