Light Pollution

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

• International Dark sky Association (IDA)
  www.darksky.org
• North Carolina Section www.ncdarksky.org

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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!

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The basic problem Sky Glow

• Light from fixtures reflects off particles in the
  skySky Glow.
• Large cities visible from tens of miles.
• The stars are not brighter in the countrythe sky
  is darker!

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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!

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The Global Problem
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Light Made in the USA
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Boone, 35 years ago
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today
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My Concern our Dark Sky Observatory Off the
Blue Ridge Parkway, near Phillips Gap
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• 32-inch Telescope
• Lab for three astronomers and their students
• 500,000 investment

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Dome and Cline Visitor Center
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The Horsehead Nebula
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M13 Globular Cluster
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Research Planetary Search

• Searching for planets in eclipsing binary star
  systems
• 100k National Science Foundation grant
• Another 150k in NASA grant funds

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Where does the sky glow come from?

• Poor fixture design
• Lack of shielding
• Overlighting
• Poor installation
• Market Pressure

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Fixtures Good, Bad and Ugly

• Cut Off street lighting
• Full Cut Off parking lot lights
• Floodlights

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Floodlights

• Almost horizontal
• No shielding
• At night

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Floodlight used in ATMs

• Glare! Could you see a criminal?
• He can see you

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Best Full Cut Off (FCO) Fixtures

• Shoebox design.
• Why do you think they are chosen?
• Appearance in the daytime!
• At night

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Billboards the Bad Way

• Uplighted
• Most light reflected into the sky
• Often on all night

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Better for the sky, but

• Glare spot (illustrates the sky problem, though)
• Fixture shadow in daylight.
• Harder to maintain?

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Roadway lighting-overhead glare
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Sag Lens - Cobra heads

• Filament below reflector
• Glaring to driver
• Light polluting

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Better, Full Cut Off Fixtures

• No light above horizon
• Non-glaring to drivers, too!
• May require more poles per mile
• At night

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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

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The Glare at Night (From High, Too!)
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Solution Sky Cap

• GE prototype shown
• Hubbell available
• Full Cut Off
• See results

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The Capped Light at Night
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The Data
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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 white to get color
  rendition

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Decorative Street Lighting

• Acorns shown
• Available with pie plate internal reflector
• Consider a FCO like the GE Salem (demo)
• Not a major impact

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Sidewalk Lighting

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

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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

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Sports Lighting

• Usually done poorly with lots of light pollution
  and light trespass.
• Can be done well as shown here, using fixtures
  like .

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Musco fixtures

• Costs 100/fixture

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Gas Station Canopies
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• 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.

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Compare to This

• This station 35fc
• Large diffusers make bulbs easy on the eyes

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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

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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.

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Lighting Ordinances Towns Counties

• Small towns and counties simple ordinance can
  get 90 of the gain
• Downlighted signs
• Caps on security lights
• Limits on gas stations (lt 40 fc max)
• 0.5 to 1 fc trespass at property lines
• Full cut off fixtures required on streets and
  lots
• No floods (or must be shielded)
• General limit (in excess of need)

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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 www.darksky.org
  (thorough but a bit much)
• Attend an ordinance-writing workshop (?)
• Hire a consultant.

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Concluding

• Like the background on this presentation, lets
  make the orange glow of sodium vapor go away.
• Thank you for your time and attention.