IDA-Colorado section news and upcoming events   2014-08-13

For a discussion of UNITS used in lighting (lumens, nits, foot-candles, etc) -- see end of page.

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A useful link to Colorado city, county, state lighting regulations:
Colorado IESNA 

For more information, visit the International Dark Sky Association homepage at www.darksky.org,


The issue: GLARE, LIGHT TRESPASS AND EXCESSIVE SKYGLOW
        Our premise: EXCESSIVE SKY GLOW OVER CITIES IS THE MANIFESTATION OF LESS THAN IDEAL ENGINEERING AND MANAGEMENT OF OUR ELECTRICAL AND LIGHTING RESOURCES, MOST OF WHICH CAN BE CORRECTED.

GLARE: The 8th edition of the IESNA Lighting Handbook (1993) defines glare as the sensation produced by luminance within the visual field that is sufficiently greater than the luminance to which the eyes are adapted to cause annoyance, discomfort or loss of visual performance and visibility. It stands to reason, then, that any good outdoor lighting design will minimize glare. If the light source itself is more apparent than what it is illuminating, then you have bad lighting. -- from the Dark Sky Association homepages.

Light TRESPASS is light that is distributed where it is not wanted or needed. Street lighting, for example, should light just streets and sidewalks, not shine into second floor bedroom windows or illuminate rooftops. Also known as spill light, light trespass occurs whenever light shines beyond the intended target and onto adjacent properties. -- from the Dark Sky Association homepages.

UPLIGHT is, in the truest sense of the word, wasted light. Light that goes directly up into the night sky is "lost in space" and serves no useful purpose. Uplight is the bane of astronomers and the occasional stargazer because atmospheric scattering artificially brightens the night sky, making distant celestial light sources difficult or impossible to see. Uplight often results from light fixtures which also produce glare and light trespass. -- from the Dark Sky Association homepages.

And from NEMA: "FULL CUTOFF" fixtures are those that allow "no light at or above a horizontal plane located at the bottom of the luminaire" (lamp plus fixture).  In any event, the idea is simple - aim the light where and when it is needed, and don't send the light upwards or across property lines.

NEWS:
DECLARATION IN DEFENCE OF THE NIGHT SKY AND THE RIGHT TO STARLIGHT -- Proceedings - Starlight 2007 Conference

"The sky, our common and universal heritage, is an integral part of the environment perceived by humanity. Humankind has always observed the sky either to interpret it or to understand the physical laws that govern the universe. This interest in astronomy has had profound implications for science, philosophy, religion, culture and our general conception of the universe". Proclamation of 2009 as International Year of Astronomy. UNESCO General Conference. Paris 2005.

“Persons belonging to future generations have the right to an uncontaminated and undamaged Earth, including pure skies; they are entitled to its enjoyment as the ground of human history of culture and social bonds that make each generation and individual a member of one human family.”

Universal Declaration of Human Rights for Future Generations. La Laguna, 1994. Website: STARLIGHT: International Initiative in Defence of the Quality of the Night Sky as Mankind’s Scientific, Cultural and Environmental Righs

0. Compilation of regional night sky photometry HERE
1. Denver City and County implemented new building codes including updated lighting regs... details available at website DENVERGOV.ORG and search for Lighting Regulations
2. Useful links to Colorado city, county, state lighting regs:
Colorado IESNA and select link to LIGHTING CODES, near end of left column.


WE **CAN** REDUCE SKYGLOW (the combined effect of light pollution), LIGHT TRESPASS AND GLARE, AND AGAIN SEE THE MILKY WAY EVEN FROM Metro DENVER!  WE NEED LIGHT POLLUTION SOLUTIONS!


LIGHT POLLUTION refers to wasteful and excessive electric lighting that blocks our view of the night sky.

Light TRESPASS and GLARE refer to unwanted and harmful lighting.

During 2001, the Colorado Legislature agreed and modified state law to address these issues: SECTION 2, ARTICLE 82 OF TITLE 24, COLORADO REVISED STATUES IS AMENDED BY THE ADDITION OF A NEW PART TO READ: PART 9, OUTDOOR LIGHTING FIXTURES.

Astronomers are NOT AGAINST SAFETY, but are very worried about destruction of the night sky by lighting that shines uselessly into the sky, wasting money and depriving everyone of their cosmic birthright, not to mention causing inferior sleep and melatonin disruption. Badly aimed light also produces trespass nuisance, and disabling glare -- especially for older people.

The simplest solution also saves money: add a shield on top of new lighting, to direct all of the light toward the ground where it is needed.

Also, the use of motion sensors and timers reduce the cost of lighting to only when it is really needed.


PAST EVENTS -- 2005 Dec: Pueblo County adopts stricter lighting regs. Link: http://www.co.pueblo.co.us/planning/planning_cases/TA%202005-003/Final%20Proposed%20Outdoor%20Lighting%20Regulation.pdf
2005 Nov: Arvada City adopts new lighting code language, www.arvada.org
2005 Sept. Regional IDA workshop, Yellowstone Nat Park
2004 Sept. 17 WORKSHOP, Frisco, Colorado:
Topics/Speakers included:
The vanishing Colorado night sky, Robert Stencel; Practical solutions for light pollution, Nancy Clanton; Crime prevention through environmental design, John Minor; Lighting Ordinance process case study, Joani Matranga & Jill Peterson
You might find local lighting codes and regs interesting (2014): STATE and COUNTY and CITY lighting regs and proposals
House bill 1160 as introduced Colorado Legislature, Jan.2001; Rationale; and how to contact your elected state reps here in Colorado:

The 1999 TEXAS LAW signed by George W. 'hissef': (& search for 1999 HB 916)
and the Texas Effective Outdoor Lighting Council
and other City, County and State lighting regs
A recent composite of EARTH AT NIGHT from space (dmsp):
and how to contact your 2014 elected state reps here in Colorado.

A few terms defined, from the Dark Sky Association homepages:

GLARE: The 8th edition of the IESNA Lighting Handbook (1993) defines glare as the sensation produced by luminance within the visual field that is sufficiently greater than the luminance to which the eyes are adapted to cause annoyance, discomfort or loss of visual performance and visibility. It stands to reason, then, that any good outdoor lighting design will minimize glare. If the light source itself is more apparent than what it is illuminating, then you have bad lighting.

Light TRESPASS is light that is distributed where it is not wanted or needed. Streetlighting, for example, should light streets and sidewalks, not shine into second floor bedroom windows or illuminate rooftops. Also known as spill light, light trespass occurs whenever light shines beyond the intended target and onto adjacent properties.

UPLIGHT is, in the truest sense of the word, wasted light. Light that goes directly up into the night sky is "lost in space" and serves no useful purpose. Uplight is the bane of astronomers and the occasional stargazer because atmospheric scattering artificially brightens the night sky, making distant celestial light sources difficult or impossible to see. Uplight often results from light fixtures which also produce glare and light trespass.

And from NEMA: FULL CUTOFF fixtures are those that allow "no light at or above a horizontal plane located at the bottom of the luminaire" (lamp plus fixture).


Contact Prof. Stencel with questions. Visit the DU Observatories: Chamberlin and Mt.Evans.
Keywords: light pollution, glare, trespass, melatonin, astronomy, astrophysics, astronomy, astrophysics, observatory, infrared, telescopes, universe, planets, stars, comets, Denver ...

UNITS sometimes used in lighting --

LUMINANCE: refers to the OUTPUT of a source.  Often a "blackbody" or Planckian approximation is used, where Luminance is a function of temperature.  Many lamps are rated for their 'color temperature' - with daytime (solar) ~5800K, tungsten ~2500K, blue-white > 6000K, etc.  These numbers are what lighting designers worry about.  ALL measures have explicit or implicit WAVELENGTH dependence, but often the visible light response of the human eye is assumed.

CANDELA (cd): 1/683 Watt per ster-radian (sr) at 5.4E14 Hz (~visible light).  The ster-radian is the angular area (or solid-angle) defined by a spherical segment one radian (57.3 degrees) on a side, centered on the light source.  The entire sphere around a source has 4 pi ster-radians of solid angle extent.  

LUMENS = flux from 1 cd per sr.  Modern lightbulbs including CFLs often have Lumen ratings printed on their packaging, e.g. 2000 Lumens @ 4500K. 

LUX = luminous emittence (lumens/sq-meters), but can also be used for illumination (see below & Table 2, wiki link below).

NITS: candelas per meter-squared.  A laptop LCD screen might produce 300 nits.  Theatrical tradition is to use the "foot-Lambert" = 3.4 cd/meter-squared.

Magnitudes, used astronomically, are similar, with m_V = 0 equal to 2.54E-6 lux at the top of our atmosphere (no extinction).

Similarly, Intensity, Flux, Emissivity and/or Radiance refers to quantifying the source output.  Intensity can be expressed in cgs units as erg/cm2/s/Hz/sr, and in MKS/SI units -- http://en.wikipedia.org/wiki/Light#Units_and_measureshttp://old.nightwise.org/sqm.htm 

ILLUMINATION refers to the light measured at a surface some distance from the source of light.  These numbers are what quantify glare and light-trespass in the case of badly designed lighting.

FOOT-CANDLES: lumens/sq-foot, somewhat archaic but still common in many municipal codes addressing lighting.  Full moon light delivers 0.01 fc on the ground.  Denver streetlights deliver 2 or so fc on adjacent turf.  Overlit outdoor facilities exceed 20plus fc on adjacent areas.

LUX = measures light incident on a surface, the illumination per meter-squared per lumen, proportional to Watts per meter-squared per ster-radian.

Many additional units exist: Stilbs, Rayleighs, Lamberts, m_10, Blondels, Skots,Brils, and others.  Ultimately these should all be related to fundamental physics units like Joules and Watts, etc.  For starters, see: http://en.wikipedia.org/wiki/Light#Units_and_measures , http://en.wikipedia.org/wiki/Stilb_(unit) , http://en.wikipedia.org/wiki/Rayleigh_(unit) , http://en.wikipedia.org/wiki/Lambert_(unit) , http://old.nightwise.org/sqm.htm .

For more information, visit the International Dark Sky Association homepage at www.darksky.org.