Light Pollution Dan Caton –President, North Carolina Section of the International Dark-Sky Association (NCIDA) NC-APA Summer Planning Institute 8/1/01

Organizations International Dark – sky Association (IDA) North Carolina Section

Objectives of This Presentation Show why astronomers are concerned and involved. Show what the problems are, with examples. Present some solutions to the problems. Ruin your view of the illuminated nightscape, forever!

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 in the country—the sky is darker!

A related problem: Glare Light directly seen from fixture is called “glare” Headlights are a familiar example. This … is glare Sadly, equated with good lighting!

The Global Problem

Light “Made in the USA”

Boone, 35 years ago…

… today

My Concern: our Dark Sky Observatory Off the Blue Ridge Parkway, near Phillips Gap

32-inch Telescope Lab for three astronomers and their students $500,000 investment

Dome and Cline Visitor Center

The Horsehead Nebula

M13 Globular Cluster

Research: Planetary Search Searching for planets in eclipsing binary star systems $100k National Science Foundation grant Another $150k in NASA grant funds

Where does the sky glow come from ? Poor fixture design Lack of shielding Overlighting Poor installation Market Pressure

Fixtures: Good, Bad and Ugly Cut Off street lighting Full Cut Off parking lot lights Floodlights

Almost horizontal No shielding At night …

Floodlight used in ATMs Glare! Could you see a criminal? … He can see you…

Best: Full Cut Off (FCO) Fixtures “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…) Fixture shadow in daylight. Harder to maintain?

Roadway lighting-overhead glare

Sag Lens - Cobra heads Filament below reflector Glaring to driver Light polluting

Better, Full Cut Off 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 problems Installed by amateurs and utilities

The Glare at Night (From High, Too!)

Solution: Sky Cap GE prototype shown Hubbell available Full Cut Off See results …

The Capped Light at Night

The Data

Car Sales Lots Often grossly overlit This one at Fc on lot, 65 on road Use astronomically unfriendly metal halides Can use sodium with 10% white to get color rendition

Decorative Street Lighting “Acorns” shown Available with “pie plate” internal reflector Consider a FCO like the GE Salem (demo) Not a major impact

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

Wall Packs One of the worst fixtures for pollution as well as glare Are available in FCO (see samples here) What is the point of these?  Or 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

IES RPA is 5 fc in dark environments, 10 in bright. This one ~60 fc. These are a danger – you are nightblind for several minutes after leaving and may leave headlights off. Danger to drivers passing by. These are actually horizontal billboards Bright metal halides with small diffusers make it worse than the average brightness suggests.

Compare to This This station ~ 35fc Large diffusers make bulbs easy on the eyes

An Almost Record … Blowing Rock required a lighting plan… Plan had peaks over 150 fc! Would not have even met existing 1-fc at property line

DOT Solutions Specify FCO on roadways so they are not lost in the bid process. Designate new highways as scenic to prevent billboards. Get legislation passed to forbid private lighting from interfering with driving.

Lighting Ordinances: Towns & Counties Small towns and counties: simple ordinance can get 90% of the gain: 1.Downlighted signs 2.Caps on security lights 3.Limits on gas stations (< 40 fc max) to 1 fc trespass at property lines 5.Full cut off fixtures required on streets and lots 6.No floods (or must be shielded) 7.General limit (“in excess of need”)

Lighting Ordinances: Cities Cities: Careful, detailed approach probably necessary. An approach: make part of zoning, so they have to submit a lighting plan in order to get a conditional use permit. Enforcement and due process is often easer this way, too. IDA Code Handbook on the web at (thorough but a bit much) Attend an ordinance-writing workshop (?) Hire a consultant.

Concluding… Like the background on this presentation, let’s make the orange glow of sodium vapor go away. Thank you for your time and attention.