Light Pollution: a Primer
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Transcript of 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”
What’s Wrong With this Picture?
Boone, 35 years ago…
… today
Even at Kitt Peak
Charlotte…
Courtesy Spencer Rackley
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 …
Floodlight used in ATMs
• Glare! Could you see a criminal? …
• He can see you…
Better: Full Cut Off (FCO)
• “Shoebox” design• Why do you think
they are chosen? …
• Appearance in the daytime!
• At night …
Burger King, Tucson
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
Sidewalk Lighting
• Post-top fixtures like these here on campus are often very glaring…
• … there is more to lighting than just foot-candles!
Billboards: the Bad Way
• Uplighted• Most light reflected
into the sky• Often on all night
Roadway lighting: overhead glare
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
The Glare at Night (From High, Too!)
Solution: Sky Cap
• GE SkyGard shown• Hubbell available• Total FCO• See results …
The Capped Light at Night
The Data
Private Security Lights
This “1973” shot impossible today!
“Space Jam”
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
Gas Station Canopies
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!
• Write letters to your newspaper….
• Teach your friends about good and bad lighting–point it out when you are out with them at night. (Spoil their view…)
• Make a difference! Start a project to get owners of “security” lights to have sky caps installed on them.
• 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.
Concluding…• Like the background on this presentation, let’s
make the orange glow of sodium vapor go away.