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Light Pollution: a Primer

Light Pollution: a Primer. 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—the sky is darker!. The Global Problem. Light “Made in the USA”.

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Light Pollution: a Primer

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  1. Light Pollution: a Primer

  2. 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—the sky is darker!

  3. The Global Problem

  4. Light “Made in the USA”

  5. Boone,NC 35 years ago…

  6. … today

  7. The Horsehead Nebula

  8. M13 Globular Cluster

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

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

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

  12. Sidewalk Lighting • Post-top fixtures like these here on campus are often very glaring… • … there is more to lighting than just foot-candles!

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

  14. Better for the sky, but… • Glare spot (illustrates the sky problem, though…)

  15. Roadway lighting-overhead glare

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

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

  18. “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

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

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

  21. The Capped Light at Night

  22. The Data

  23. Private Security Lights

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

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

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

  27. … Musco fixtures • Costs ~$100/fixture

  28. Gas Station Canopies

  29. Compare to This • This station ~ 35fc • Large diffusers easy on the eyes • Easy on the camera, too…

  30. How You Can Help • Look at your own lights–are they needed? Could you have it capped? Put it on a switch, timer or a motion sensor. Put in a lower wattage bulb. • Where do you eat out? Do the restaurants have glaring lights? If so, complain! …

  31. Are there some roadside lights that bother you as you try to drive? Complain! • Is there a street light that shines into your window at night? Call up the utility and ask for them to put a sky cap on it. Don’t settle for simple spray painting of the fixture’s lens! • Is there a street light that shines into your window at night? Call up the utility and ask for them to put a sky cap on it. Don’t settle for simple spray painting of the fixture’s lens! • Spend some time at www.darksky.org and become (more of) an expert! Join the IDA. • Write letters to your newspaper….

  32. Teach your friends about good and bad lighting–point it out when you are out with them at night. • Make a difference! Start a project to get owners of “security” lights to have sky caps installed on them. • Is there a street light that shines into your window at night? Call up the utility and ask for them to put a sky cap on it. Don’t settle for simple spray painting of the fixture’s lens! • Spend some time at www.darksky.org and become (more of) an expert! Join the IDA. • Realize that you are the ones with rights to speak for (“pursuit of Happiness” [Dec.Ind., par.2]). • Develop a local ordinance.

  33. Concluding… • Like the background on this presentation, let’s make the orange glow of sodium vapor go away.

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