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.