Light Pollution: a Primer

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Light Pollution a Primer
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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 here in the
  countrythe sky is darker!

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The Global Problem
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Light Made in the USA
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Boone,NC 35 years ago
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today
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The Horsehead Nebula
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M13 Globular Cluster
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Where does the sky glow come from?

• Poor fixture design
• Lack of shielding
• Over-lighting
• Poor installation
• Market pressure

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Floodlights

• Almost horizontal
• No shielding
• At night

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Better Full Cut Off (FCO)

• 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)

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Roadway lighting-overhead glare
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Cobra heads

• Filament below reflector
• Glaring to driver
• Light polluting

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Better, FCO 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 problem
• 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
• Total FCO
• 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 while to get color
  rendition

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Wall Packs

• One of the worst fixtures for pollution as well
  as glare
• Are available in FCO
• What is the point of 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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Compare to This

• This station 35fc
• Large diffusers easy on the eyes
• Easy on the camera, too

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How You Can Help

• Teach your students about the importance of dark
  skies by including a light pollution lecture in
  your astronomy course (we are handing out a
  PowerPoint presentation suitable for this, ask us
  for one!)
• Look at your own lightsare 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!

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• 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. Dont settle for
  simple spray painting of the fixtures lens!
• 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. Dont settle for
  simple spray painting of the fixtures lens!
• Spend some time at www.darksky.org and become
  (more of) an expert! Join the IDA.
• Write letters to your newspaper.

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• Teach your friends about good and bad
  lightingpoint it out when you are out with them
  at night.
• Make a difference! Start a project to get owners
  of security lights to have sky caps installed
  on them.
• 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. Dont settle for
  simple spray painting of the fixtures lens!
• 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.

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Lighting Ordinances

• A simple ordinance can get 90 of the gain
• FCO, no floods (or or shielded floods)
• Down-lighted signs
• Caps on security lights
• Limits on gas stations (lt 35 fc max)
• 0.5 to 1 fc trespass at property lines
• General limit (in excess of need)
• Coming Model Lighting Ordinance (IDA and Jim
  Benya, Benya Lighting Design)

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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, and...
• Lets make some changes!