Good and Bad Lighting in the Central Valley

Good and Bad Lighting in the Central Valley
Skykeepers
skykeepers.org founded September 1, 1999

The major reason Light Pollution is so bad in the Central Valley is the type of light fixture used by municipalities followed by commercial, industrial, residential and to some extent sports lighting.
The energy wasted by bad fixtures, to some extent contribute to Global Warming.

Bad Light Fixtures used by some Municipalities -

GOOD and BAD side by side example

Drop Lens Cobra (right) Flat Lens Cobra (left)

Drop Lens Cobra "BAD" (left) and Flat Lens Cobra "GOOD" (right)

This photo shows one of the main reasons we have Light Pollution, the use of drop lens cobra fixtures by our municipalities. It does not take expensive equipment or training to understand why drop lens cobras cause light pollution, this photo shows what happens. The photo was take in Old Town Sacramento under the I-5 over crossing. Other examples can be found under the freeway in this area.

Drop Lens Cobra (left) -
Note the shadow directly above the fixture and how bright spots extent out on each side.
If the freeway over crossing was not there this light would travel hundreds of miles beyond the fixture.
This shadow is not created by reflection from the road below but by the glass lens which extends below.
This type of fixture creates glare as drivers approach this on ramp.
This fixture wastes energy by allowing light to go in all directions.
This fixture is a major cause of light pollution.

Flat Lens Cobra (right) -
There is no shadow is visible above the fixture on the right.
It is easy to see the "cutoff" pattern of the projected light on the columns to the left and right of the fixture.
The top of the columns and the bottom of the freeway bridge remain dark compared to lower down.
Light is directed down on to the pavement below and on object that need to be illuminated.
When viewed from a distance the source of the light is not visible (glare is reduced).
This fixture conserves energy by confining all the light to objects that need to be illuminated.
This fixture protects the night sky from light pollution and prevents light trespass.

BAD

A typical Drop Lens Cobra
This fixture causes light pollution.

GOOD

A typical Flat Lens Cobra
This fixture prevents light pollution.

Fixtures commonly used for street lighting that cause light pollution

A typical Post Top Fixture Poorly controlled light pattern "scatter" causes light pollution.		A typical Acorn (Bad) Poorly controlled light pattern "scatter" causes light pollution.
Very Bad Flood Light Often referred to a off road light.		Bad Drop Lens Cobra This fixture causes light pollution.

Why do we have such bad light pollution in the central valley?
See this link pages 6,7 and 9,10 for part of the answer, City of Sacramento Standard Specifications for street light and siginals (.pdf)

Here is another link relating to the City of Sacramento, Google "light pollution" site:www.cityofsacramento.org http://www.google.com/search?hl=en&q=%22light+pollution%22+site%3Awww.cityofsacramento.org&btnG=Search

Even more telling, Google "light pollution" site:www.saccounty.net "light pollution" site:www.saccounty.net

References to Municipalities actively preventing Light Pollution and saving energy
The City of Calgary EnviroSmart Street Light Retrofit Program	Link To
Alberta municipalities embrace the energy efficiency evolution - Climate Change Central News Letter, June 2004 (.pdf)	Get File
Find Municipalities in California with Outdoor Lighting Ordinances	GoThere
"Better Lights for Better Nights" examples of good and bad lights published by the Dark Sky Society NY (.pdf 44k)	Get File
Lights in Action - Much the same lights as we have in the Central Valley	Link To

Media Coverage of Municipalities actively preventing Light Pollution
Giving back the night, Hailey has a new take on light - Idaho Mountain Express	Link To

Light Pollution and Outdoor Lighting
Light Pollution and Green House Gas in Central California - How does upward wasted light contribute to Global Warming?	GoThere
Examples of Good Outdoor Lighting Fixtures - A small sample of good fixtures.	GoThere
Dark sky friendly lighting fixtures - IDA Website	Link To
Fully shielded Roadway lighting - IDA Website	Link To

Bad Light Fixtures used in some Industrial and Commercial applications

Typical Wall Packs Poorly controlled light pattern causes Light Polllution and Light Trespass.	Sag Lens Shoebox Sag Lens allow light to escape about the horizontal causing Light Polllution and Light Trespass.	A typical Security Light Poorly controlled light pattern causes Light Polllution and Light Trespass.
Bad Lantern style fixture (high glare from the glass refractor)	Bad Lantern style fixture (high glare from the glass refractor)	A Group of Bad Fixtures Sag or Drop Lens and Acorns.

Examples of Good Outdoor Lighting Fixtures
References to Light Pollution and saving energy
Lighting tips for businesses - page on the SELENE web site	Link To
Good and Bad Light Gallery - page on the SELENE web site	Link To
Metal Halide (MH) vs High Pressure Sodium (HPS) by Susan Harder (.pdf) Sources, Surfaces and Atmospheric Scattering: The Rayleigh Scatter Index by Jefferey F. Knox & David M. Keith, FIES (.pdf)	Get File Get File
Dark sky friendly lighting fixtures - IDA Website	Link To
"Better Lights for Better Nights" examples of good and bad lights published by the Dark Sky Society NY (.pdf 44k)	Get File