Light Pollution: a Primer
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Presentation Transcript
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!
Where does the sky glow come from? • Poor fixture design • Lack of shielding • Over-lighting • Poor installation • Market pressure
Floodlights • Almost horizontal • No shielding • At night …
Better: Full Cut Off (FCO) • “Shoebox” design • Why do you think they are chosen? … • Appearance in the daytime! • At night …
Billboards: the Bad Way • Uplighted • Most light reflected into the sky • Often on all night
Better for the sky, but… • Glare spot (illustrates the sky problem, though…)
Cobra heads • Filament below reflector • Glaring to driver • Light polluting
Better, FCO Fixtures • No light above horizon • Non-glaring to drivers, too! • May require more poles per mile • At night …
“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
Solution: Sky Cap • GE SkyGard shown • Hubbell available • Total FCO • See results …
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
Wall Packs • One of the worst fixtures for pollution as well as glare • Are available in FCO • What is the point of these?
Sports Lighting • Usually done poorly with lots of light pollution and light trespass. • Can be done well as shown here, using fixtures like ….
… Musco fixtures • Costs ~$100/fixture
Compare to This • This station ~ 35fc • Large diffusers easy on the eyes • Easy on the camera, too…
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! …
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….
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….
Lighting Ordinances • A simple ordinance can get 90% of the gain: • FCO, no floods (or or shielded floods) • Down-lighted signs • Caps on security lights • Limits on gas stations (< 35 fc max) • 0.5 to 1 fc trespass at property lines • General limit (“in excess of need”) • Coming: Model Lighting Ordinance (IDA and Jim Benya, Benya Lighting Design)
Concluding… • Like the background on this presentation, let’s make the orange glow of sodium vapor go away.
