Light Pollution: a PrimerDan Caton

and

Lee Hawkins

Lighting: Opposite of ImagingWhat we do What you do

•My Concern: our Dark Sky Observatory

•In the Blue Ridge Mountains of western North Carolina

•32-inch Telescope

•Lab for four astronomers and their students

•$1M investment

Dome and Cline Visitor Center

100,000 hobbyists

                                     

Everyman…

Just as important

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!

Global Problem

Light “Made in the USA”

What’s Wrong With this Picture?

Closer to home

You are here!

Boone, 40 years ago…

… more recently

Even at Kitt Peak

Charlotte…

Courtesy Spencer Rackley, III

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 …

Here at the Ramada

Last 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, TucsonIn Boone…

New Advance Auto, Boone

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 on ASU campus are often very glaring…

• ASU has now adopted the Night Sky optics option

Acorns

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

More options!

Residential Entry

• Ditto: not many FCO fixtures available

• This unit also by Minka

• Soffit lights better—also do not draw bugs

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

Health concerns

• Baby sea turtles attracted to street light

• Cancer and melatonin production in people

This “1973” shot impossible today!

“Space Jam”

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

… like this (Tampa)

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 ….

Fixtures with light control

Gas Station Canopies

Compare to This

• This station was ~ 35fc

• Large diffusers easy on the eyes

• Easy on the camera, too.

• Unfortunately they have slowly replaced these fixtures with the glaring type (for now, given the ordinance)

How You Can Help• Support the creation of ordinances that

require lighting to be designed and of appropriate lighting levels and glare control

• Steer customers to better lighting!• Request better designs from lighting

manufacturers—there is a real dearth of, for example, FCO driveway post top units

• Teach your customers and suppliers about this issue

Concluding…• Like the background on this presentation, let’s

make the orange glow of sodium vapor go away.