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[DSLF] Digest Number 575
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There are 16 messages in this issue.
Topics in this digest:
1. Re: NY Veto
From: Gary Citro <callisto@optonline...>
2. Re: A few things we should know about light pollution!
From: "David Keith" <keithd@resodance...>
3. Re: Re: Lighting cost calculator
From: "David Keith" <keithd@resodance...>
4. Re: A few things we should know about light pollution!
From: "ctstarwchr" <ctstarwchr@aol...>
5. Light Pollution and Breast Cancer
From: Anthony Arrigo <Anthony.Arrigo@CampusPipeline...>
6. Re: Re: Lighting cost calculator
From: "Terry McGowan" <lighting@ieee...>
7. FAA Tower Lighting Requirements
From: "Glendon L. Howell" <glendonhowell@compuserve...>
8. Re: FAA Tower Lighting Requirements
From: Barry Johnson <johnsonb@ivwnet...>
9. Re: Re: Lighting cost calculator
From: Barry Johnson <johnsonb@ivwnet...>
10. Re: FAA Tower Lighting Requirements
From: "ctstarwchr" <ctstarwchr@aol...>
11. Re: Help with Response to Goveneors Office and Legislators
From: ctstarwchr@aol...
12. R: R: A few things we should know about light pollution!
From: "Pierantonio Cinzano" <info@inquinamentoluminoso...>
13. Bird Migration by Constellations - what if they can't see them??
From: chris@tunnah....uk
14. RE: Re: Lighting cost calculator
From: "Peel, Bill D." <BPeel@Lithonia...>
15. Re: A few things we should know about light pollution!
From: ctstarwchr@aol...
16. Re: A few things we should know about light pollution!
From: ctstarwchr@aol...
________________________________________________________________________
________________________________________________________________________
Message: 1
Date: Thu, 07 Feb 2002 07:31:01 -0500
From: Gary Citro <callisto@optonline...>
Subject: Re: NY Veto
Fabio Falchi wrote:
> Isn't it possible to sue the Governor for the added
> cost that NYS will pay doing BAU in outdoor practices
> vs. the economy of the FCO fixtures?
I dpn't know what "BAU" is, but one of the reasons that the NY bill was
vetoed was that despite our pleas to various sectors, we were unable to come
up with authoritative data that FCO fixtures actually save energy.
Therefore, there are no grounds for suing the Governor.
It's the chicken and the egg. You can't sue an official for not signing a
law because he's not breaking a law yet.
Furthermore, due to Pataki's appropriate handling of events on Sept. 11th,
he is a shoe-in for reelection this November, which means we will be dealing
with him for a long time. I personally don't believe we should go any
further than making our disatisfaction known, and back it up by *data* next
time around.
BTW, Selene has *just* started an open listserve of our own, for those who
want to network in the NY effort.
To join, send an email message to: majordomo@ggw...
Leave the subject line blank
In the body of the message, type:
subscribe sensiblelighting-list your_email_address
(obviously, you put your email address in place of "your_email_address")
We are stronger than ever!!
Gary Citro
http://selene-ny.org
________________________________________________________________________
________________________________________________________________________
Message: 2
Date: Thu, 7 Feb 2002 08:16:11 -0700
From: "David Keith" <keithd@resodance...>
Subject: Re: A few things we should know about light pollution!
I want to add a point of information and a point of discussion.
The definitions of the cutoff classifications for the IESNA are:
Full cutoff: intensity at or above horizontal is 0 (zero) cd, maximum
intensity value between 80-90 degrees elevation is no more than 10% of the
value of the rated lumens, at any angle around the luminaire
Cutoff: maximum intensity value at or above horizontal is 2.5% of the value
of rated lumens, maximum intensity value between 80-90 degrees elevation is
no more than 10% of the value of the rated lumens, at any angle around the
luminaire
Semi-cutoff: maximum intensity value at or above horizontal is 5% of the
value of rated lumens, maximum intensity value between 80-90 degrees
elevation is no more than 20% of the value of the rated lumens, at any angle
around the luminaire
Source is the ANSI/IESNA RP-8-2000, as well as the IESNA Lighting Handbook,
9th ed.
As for the conclusion that the angles of light emission from luminaires is
critical to evaluating light pollution (or that engineering evaluations are
"wrong"):
My previous work is quite clear that it is evaluating "uplight" - that
characteristic of the lighting system which both generally corresponds to
skyglow and that is under the design control of lighting designers. The
work discussed below addresses *skyglow*, but apparently omits the
intermediate step: how uplight reaches the atmosphere to contribute to
skyglow.
Unless we are in the open desert (or assuming that the world is a billiard
ball) it is reasonable to see that - depending on the physical environment -
some/much/all of the flux from the luminaires and the directly illuminated
surfaces will have further interaction(s) with surfaces before reaching the
sky. First approximations of cavity effects indicate that anywhere from 10%
to as much as 99% of uplight flux could be absorbed instead of contributing
to skyglow. Certainly the effect is significant in urban and forrested
areas, and for example in the canyons of Colorado - where absolutely ZERO
light will be escaping into the sky at angles anywhere near horizontal. Of
course there are areas where this is not the case - seacoast, plains,
desert. The relative weighting of such different surroundings seems at
first view to be a massively complex evaluation.
Furthermore the geometry of developed areas indicates that - coming directly
from luminaires or reflections - flux "near horizonal" is *much more likely*
to be incident onto a surface than flux at higher elevations.
In any case it is perfectly obvious that this intermediate step - where
uplight becomes a possible contributor to skyglow - *may be* the dominant
factor in establishing what is the contribution from uplight to skyglow.
This intermediate step is fundamentally based on pure assumptions, which may
be extremely varied and are very significant to the results. Therefore it
seems to be very difficult to make any useful conclusions about it, such as
the direction of uplight which does reach the sky. What we should recognize
is that the direction from the luminaire or the intial reflection is NOT
necessarily the direction the flux is going when it reaches the sky.
David Keith
----- Original Message -----
From: "Pierantonio Cinzano" <info@inquinamentoluminoso...>
To: <DarkSky-list@yahoogroups...>
Cc: "International Dark-Sky Association" <ida@darksky...>
Sent: Wednesday, February 06, 2002 2:07 PM
Subject: R: [DSLF] A few things we should know about light pollution!
{editted for brevity}
> it is good that a paper make clear that a lumen of light spilled near the
> horizon pollute about three times than the same lumen diffused on the
> asphalt.
{break}
> If we want minimizing light pollution, the pollution produced by light
> emitted directly above the horizon must be very small or negligible in
> respect to the pollution due to reflexion by lighted surface (which is
> necessary to the lighting process). If they are equal for a fixture with
an
> upward flux of 5.5% and if we want reduce the direct pollution at least at
> 1/10 of the reflected pollution, then we need fixtures emitting less than
> 0.55% of upward flux. This means that semi-cut-off fixtures are ruled out
> and you need full cut off.
{break}
> As the cited paper Cinzano-Diaz Castro showed, the emission at small
> elevations (under 45 degrees) is responsible for almost all the artificial
> sky brightness at zenith outside few kilometers from the sources
> (http://debora.pd.astro.it/cinzano/papers.html). This means that small
> angles emission is a main source of the artificial brightness in the
> country, in astronomical sites outside cities, and sometime also inside
> towns when they are located in densely populated areas.
{break}
> The demonstrations by light engineers that "with less stringent optical
> cutoff, the poles can be more spaced for a same uniformity and the overall
> fraction of light that goes up, including the ground reflection, can be
> reduce by up to 20%" are wrong (or misunderstood)for this and for many
other
> reasons, some of which I explained clearly at the CIE TC4-21 meeting in
> Athens. Probably at New York nobody sufficiently expert to demolish the
> wrong thesis of light polluters has been consulted by politicians. In any
> case it looks like the Governor was in touch with them.
>
> The point is that you must minimize not only the total pollution, which is
> an integrated parameter, but also this ratio at any angle. In fact the
> Lumbardy Law in Italy does not limit the upward flux ratio, which is an
> integrated quantity, but it limit the upward intensity per unit flux
(which
> depends on the angle) at any angle over the horizon. And there are no
limits
> at all under the horizon.
>
> Cheers,
>
> Pierantonio
>
> ------------------------------------------------------------------
> PIERANTONIO CINZANO
> Istituto di Scienza e Tecnologia dell'Inquinamento Luminoso - ISTIL
> Light Pollution Science and Technology Institute
> e-mail: cinzano@inquinamentoluminoso...
> cinzano@lightpollution...
> web: http://www.pd.astro.it/cinzano/
> http://www.inquinamentoluminoso.it
> http://www.lightpollution.it/dmsp/
> http://www.istil.it
> ------------------------------------------------------------------
> -------------------------------------------------------------------------
> PIERANTONIO CINZANO
> International Dark-Sky Association - Italia
> Direttore Scientifico
> e-mail: cinzano@inquinamentoluminoso...
> web: http://www.inquinamentoluminoso.it
> ------------------------------------------------------------------------
>
>
> -----Messaggio originale-----
> Da: Yvan Dutil [mailto:yvan.dutil@sympatico...]
> Inviato: mercoledì 6 febbraio 2002 2.06
> A: DarkSky-list@yahoogroups...
> Oggetto: [DSLF] A few things we should know about light pollution!
>
>
> This a text I have prepare for the next dark-sky newsletter.
Unfortunately,
> due to a lack of place,
> we will have to wait up to next edition to have it publish. Meanwhile, I
> will
> have probably publish
> my research paper in PASP. By the way, I am open to any comment.
>
> Yvan Dutil
>
> --------------------------------------------------------------------------
--
> ----------
>
> Recently, two major legislations against light pollution have been
rejected.
> One in the New York state, the other in the Czech Republic, One of the
> reasons invoked was lack of scientific justification for full cut-off
lamp.
> Arguments invoked by astronomers (light above the horizon=pollution)
> backfired in face of analysis done by lighting engineers demonstrating
that
> with less stringent optical cutoff, the poles can be more spaced for a
same
> uniformity and the overall fraction of light that goes up, including the
> ground reflection, can be reduce by up to 20% (Remande 2000).
Unfortunately,
> these two conflicting conclusions are based on simplistic model of the
light
> pollution. Our understanding of the light pollution must improve otherwise
> the same scenario will repeat again.
>
> Common sense is that up-going light equals light pollution. The classical
> example is an old fashion lamp that emits directly 35% of the light up,
65%
> down of which 10% is reflected up. Overall, 45% of the light ends up
> illuminating the sky. Then with full cut-off optics, the direct emitted
> light
> goes down to 0%, and only the light reflected on the ground goes up, 10%.
In
> consequence, we would expect a spectacular 88% in reduction of the overall
> pollution. Lighting engineer got even further, by following the
engineering
> norms and applying their model for road illumination, they came down to
the
> conclusion that light pollution can be minimized of you use semi-cutoff
> optics, which allows a few percents of light to spill above the horizon.
>
> Unfortunately, this model does not take account of a very simple fact:
light
> emitted at low angle is more polluting that light emitted at the vertical.
> Simply, there is more air in the direction of the horizon than at the
> zenith,
> which provide more chance for a photon to get diffused. Don't forget, that
> in
> essence light pollution is not a problem of light going up but a problem
of
> light that was going up but got diffused on the ground. In consequence, it
> has been shown up by Pierantiono Cinzano & Francisco Javier Diaz Castro,
> that
> most of the light pollution is produce by light emitted at angle below 10
> degrees above the horizon. Unfortunately, the results of this key paper
are
> presented in a form that renders them impractical for engineering
practice.
>
> In order, to address this issue I have develop a simple model of
atmospheric
> diffusion (Dutil 2002). It is essentially the same model as the one
develop
> by Garstang and use recently by Cinzano et al. to produce their world
atlas
> of light pollution. With some simplifications that ease the calculation
but
> have little impact on the final result.
>
> For typical atmospheric condition, the light pollution efficiency peaks at
4
> degrees above the horizon at a value 5.85 times higher than at zenith.
> However order to evaluate the real impact of the light pollution, we have
to
> sum the contribution of every angles. I have examined three typical
emission
> functions: uniform over 10 first degrees above horizon (spilled light from
a
> good lamp), lambertian (like a reflection on pavement) and uniform (like
the
> emission of a globe). The pollution coefficients for each distribution are
> respectively 0.7950, 0.2902 and 0.4206. From these numbers we can deduce
> that a lumen of light spilled near the horizon pollution 2.74 more than
the
> same lumen diffused on the asphalt, and 1.89 times more that if it was
> emitted by an infamous globe! Readers have to be advised that this result
> have not been peer reviewed yet and in consequence should be use with
great
> care.
>
> What does this means in practice? If we used a standard albedo of 15% for
> the
> pavement, it can be shown that the reflected light will dominate the
> pollution budget if the light emitted directly above the horizon does not
> exceed 5.5%! Taken at face value this would means that lighting engineers
> are
> right and that simple cut-off optics would produce less light pollution
> since
> the only emit 2% of their light above horizon. If we recalculate the
> previous
> example with those number, we get: 35%+10%/2.74=38.65% vs 10%/2.74=3.65%.
As
> we can see, the real reduction of light pollution is 90.6% instead of 88%
as
> we have previously calculated.
>
> Is this the end of the full cut-off lamp? Nothing is less sure. First, we
> need to take account of the real amount of light spilled by lamp. Lamps
are
> rarely exactly level and this inevitably increasing the light loss. This
> factor alone is enough to favor full cut-off optics. Second, the claims
of
> engineers are based on a requirement of illumination uniformity. Real
night
> vision is more complex and rigorous modeling with probably end up with a
> different result, especially if glare is taken into account.
>
> Do not forget that better lighting practice is our ultimate goal. Once the
> physics is well understood, optimization is easy.
>
> Reference:
>
> Cinzano, P., Diaz Castro, F. J., 2000, Mem. Soc. Astro. It., 71, 251
> Cinzano, P., Falchi, F., & Elvidge, C. D. 2001, Monthly Notices of the
Royal
> Astronomical Society, 328, 689
> Dutil, Y., to be submitted to Publication of the Astronomical Society of
the
> Pacific
> Garstang, R. H. 1986, Publication of the Astronomical Society of the
> Pacific,
> 98, 364
> Garstang, R. H. 1989, Publication of the Astronomical Society of the
> Pacific,
> 101, 306
> Garstang, R.H. 1991, Publication of the Astronomical Society of the
Pacific,
> 103, 1109
> Remande, C., 2001, in Preserving the Astronomical Sky, IAU Symposium, Vol.
> 196, R. J. Cohen and W. T. Sullivan, III, eds.
>
>
>
>
>
> _________________________________________________
> To subscribe to the DarkSky List Forum send email
> to: DarkSky-list-subscribe@yahoogroups...
>
> Help save your town from obtrusive lighting --
> invite your planning and zoning department to
> join us! Ask them to visit the IDA website at
> http://www.darksky.org today!
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
>
>
> _________________________________________________
> To subscribe to the DarkSky List Forum send email
> to: DarkSky-list-subscribe@yahoogroups...
>
> Help save your town from obtrusive lighting --
> invite your planning and zoning department to
> join us! Ask them to visit the IDA website at
> http://www.darksky.org today!
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
________________________________________________________________________
________________________________________________________________________
Message: 3
Date: Thu, 7 Feb 2002 08:32:07 -0700
From: "David Keith" <keithd@resodance...>
Subject: Re: Re: Lighting cost calculator
Two additional notes:
The pulse start technology is generally available just as "vertical-only"
lamps (this may have changed over the last month/year) - but most exterior
HID lighting equipment uses horizontal lamps.
The definition of *mean lumens* is different for HPS or MH - for HPS mean is
taken at 50% of rated life, while for MH "mean" is defined as 40% of rated
life.
This "means" that comparisons between sources based on this data, such as
"maintained" efficacy of HPS vs MH, is a waste of ink/electrons - and/or
that the actual rated life of MH is 80% of the published data.
David Keith
----- Original Message -----
From: "Terry McGowan" <lighting@ieee...>
To: <DarkSky-list@yahoogroups...>
Sent: Wednesday, February 06, 2002 10:18 AM
Subject: Re: [DSLF] Re: Lighting cost calculator
> Tim, the "Pulse Start" metal halide technology is rapidly replacing the
older metal halide systems because of longer lamp life, higher efficacy, and
improved color stability. The basic difference is that the pulse-start lamp
has two electrodes rather than three. That means a different ballast, or at
least one with a starting circuit added, is required. All of the major lamp
manufacturers make the pulse-start lamps. Venture has a particularly broad
line listed.
>
> You're probably better to use the manufacturers' lamp ratings since
ratings have been changing and I don't know the age of the IDA sheet. Table
6-9 in the "Advanced Lighting Guidelines - 2001" is an average of several
manufacturers' data and should still be O.K. (the ALG can be downloaded from
http://www.newbuildings.org ). Circuit wattages and efficacies for all of
the energy-efficient HID systems are listed in Table 6-10 for both initial
and mean lamp light output.
>
> Terry McGowan
________________________________________________________________________
________________________________________________________________________
Message: 4
Date: Thu, 07 Feb 2002 18:40:15 -0000
From: "ctstarwchr" <ctstarwchr@aol...>
Subject: Re: A few things we should know about light pollution!
Skyglow is the atmospheric phenomenon caused by stray ground based
light being scattered by airborne particles suspended in the
atmosphere. At night the results of this scattering diminish our
view of the cosmos to varying degrees, much like turning on the
lights in a movie theater while the film is still rolling.
Atmospheric optics defines two main types of scattering known as
Rayleigh and MIE scatter. Rayleigh scatter occurs when participating
media (i.e., gases in the atmosphere) are smaller in diameter than
the wavelength of electromagnetic radiation (i.e. light) interacting
with them. The effect of Rayleigh scatter is inversely proportional
to the fourth power of the wavelength, therefore, short wavelengths
in the blue portion of the visible spectrum are more likely to be
scattered than long ones. The Rayleigh scattering effect makes our
daytime sky appear blue. Rayleigh scatter also causes the haze seen
at low angles near the horizon when the sun is high in the sky and it
is also what makes the sun and moon appear orange when they are near
the horizon.
MIE scattering occurs when the particle is equal or larger in size
than the wavelength of radiation interacting with it. Water vapor,
soot, and dust particles are common participating media facilitating
MIE scattering effects, which tend to influence longer wavelengths
than Rayleigh scattering does. Rayleigh scatter usually takes
precedence under most conditions, but MIE scatter dominates during
overcast conditions.
Information on Rayleigh and MIE scattering effects that may help
those researching these issues...
Atmospheric Light Phenomena
http://www.auf.asn.au/meteorology/section12.html
GEO211 Introduction to Remote Sensing
http://www.shef.ac.uk/~bryant/211lectures/2001/211L3_2001.ppt
Scientific Theory of Measurements
http://ltpwww.gsfc.nasa.gov/IAS/handbook/handbook_htmls/chapter6/chapter6.html
University of Wisconsin - Madison Institute for Environmental Studies
ATMOSPHERIC OPTICS: GIS & Remote Sensing
http://www.ersc.wisc.edu/academics/courses/IES301/handouts/301_1_1pp.pdf
http://www.ersc.wisc.edu/academics/courses/IES301/handouts/301_1_2pp.pdf
Light Scatter
http://www.cyto.purdue.edu/flowcyt/educate/ee520/tsld035.htm
Clouds & Aerosols Average Drop Size
http://www2.etl.noaa.gov/cloud_avgsize.html
Aerosol measurements by LIDAR
http://www.aero.jussieu.fr/~sparc/SPARC2000_new/PosterSess1/SessionP1_3/Bencheriff/Node2.html
ATM OCN (Meteorology) 100: ATMOSPHERIC OPTICS
http://www.aos.wisc.edu/~hopkins/aos100/homework/f01hmk05a.html
Scattering redirects photons without diminishing their intensity,
which might help to explain why light emitted at low angles above the
horizontal end up showing negative effects as far as 100 miles away
in remote and otherwise dark locations.
Clear skies and good seeing,
Keep looking up!
Cliff Haas
http://members.aol.com/ctstarwchr
________________________________________________________________________
________________________________________________________________________
Message: 5
Date: Thu, 07 Feb 2002 14:47:50 -0700
From: Anthony Arrigo <Anthony.Arrigo@CampusPipeline...>
Subject: Light Pollution and Breast Cancer
A while back, I contacted a writer about doing a story on the links
between light pollution and breast cancer. She just sent me an e-mail
indicating that she'd gotten the OK from a magazine to write such an
article. She's been doing some preliminary research on her own, but
would like to get in touch with someone who is an authority on the
subject. Any suggestions on how to make this happen???
APA
________________________________________________________________________
________________________________________________________________________
Message: 6
Date: Thu, 7 Feb 2002 17:09:11 -0500
From: "Terry McGowan" <lighting@ieee...>
Subject: Re: Re: Lighting cost calculator
You're right about the "vertical only" lamps, David. The pulse-start lamps that can be burned off-vertical also tend to be the lower wattage types --150 watts or less.
I used "mean lumens" and "mean efficacy" in the Advanced Lighting Guidelines so that the depreciation characteristics of the lamp could be taken into account when comparing lamps and systems. The mean values aren't meant to be a design factor unless someone wants to design to mean output over time.
HPS and incandescent lamps have relatively linear light output depreciation curves over time and so their mean values rightly use 50% of life as the mean point. Fluorescent and metal halide lamps typically have non-linear depreciation characteristics and 40%-of-rated-life values roughly fit the mean light output point on the curve. For some lamps, that's more of a convention than a calculation; but lamp industry practice has, at least, been consistent.
The engineering approach would have been to use what the IESNA calls the "Lamp Lumen Depreciation" (LLD) Value or the light output of the lamp at 70% of rated life. If someone is designing a system so that it doesn't drop below a certain design value, then I suppose that LLD is a good "worst case" approach -- certainly better than using the lumen output of the lamp at its rated life point.
So, the purpose was understandability rather than rigor; but I do think that mean values lead to correct comparison decisions about what systems to use based upon energy use.
Terry McGowan
----- Original Message -----
From: David Keith
To: DarkSky-list@yahoogroups...
Sent: Thursday, February 07, 2002 10:32 AM
Subject: Re: [DSLF] Re: Lighting cost calculator
Two additional notes:
The pulse start technology is generally available just as "vertical-only"
lamps (this may have changed over the last month/year) - but most exterior
HID lighting equipment uses horizontal lamps.
The definition of *mean lumens* is different for HPS or MH - for HPS mean is
taken at 50% of rated life, while for MH "mean" is defined as 40% of rated
life.
This "means" that comparisons between sources based on this data, such as
"maintained" efficacy of HPS vs MH, is a waste of ink/electrons - and/or
that the actual rated life of MH is 80% of the published data.
________________________________________________________________________
________________________________________________________________________
Message: 7
Date: Thu, 7 Feb 2002 21:17:23 -0500
From: "Glendon L. Howell" <glendonhowell@compuserve...>
Subject: FAA Tower Lighting Requirements
I recall quite awhile back there was some discussion on FAA requirements
for tower lighting. If I recall correctly, white strobe lighting was not
an absolute requirement.
Our neighborhood is now mobilizing to fight a proposed communication tower
near our neighborhood. Our Civic League President has been told it is a
requirement to have the white strobes. Can someone please point me to the
URL where I where there is FAA info on lighting requirements?
Thanks In Advance!
Glendon Howell
glendonhowell@compuserve...
Norfolk Astro Soc.
Chesapeake, VA
________________________________________________________________________
________________________________________________________________________
Message: 8
Date: Thu, 07 Feb 2002 23:29:08 -0500
From: Barry Johnson <johnsonb@ivwnet...>
Subject: Re: FAA Tower Lighting Requirements
You can download a copy of the FAA regulation on "Obstruction Marking and
Lighting" at:
http://www.faa.gov/ats/ata/ai/index.html
Barry Johnson
"Glendon L. Howell" wrote:
> I recall quite awhile back there was some discussion on FAA requirements
> for tower lighting. If I recall correctly, white strobe lighting was not
> an absolute requirement.
>
> Our neighborhood is now mobilizing to fight a proposed communication tower
> near our neighborhood. Our Civic League President has been told it is a
> requirement to have the white strobes. Can someone please point me to the
> URL where I where there is FAA info on lighting requirements?
>
> Thanks In Advance!
>
> Glendon Howell
> glendonhowell@compuserve...
> Norfolk Astro Soc.
> Chesapeake, VA
>
> _________________________________________________
> To subscribe to the DarkSky List Forum send email
> to: DarkSky-list-subscribe@yahoogroups...
>
> Help save your town from obtrusive lighting --
> invite your planning and zoning department to
> join us! Ask them to visit the IDA website at
> http://www.darksky.org today!
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
________________________________________________________________________
________________________________________________________________________
Message: 9
Date: Thu, 07 Feb 2002 23:39:59 -0500
From: Barry Johnson <johnsonb@ivwnet...>
Subject: Re: Re: Lighting cost calculator
It means that the slope of the lumen depreciation function for MH is greater
during the early life of the lamp than it is for HPS.
The rated life is unaffected by when the mean lumen output is reached during
that life .
Barry Johnson
David Keith wrote:
>
> that the actual rated life of MH is 80% of the published data.
>
> David Keith
>
>
[Non-text portions of this message have been removed]
________________________________________________________________________
________________________________________________________________________
Message: 10
Date: Fri, 08 Feb 2002 05:28:26 -0000
From: "ctstarwchr" <ctstarwchr@aol...>
Subject: Re: FAA Tower Lighting Requirements
Glen:
A link is provided to FAA Regulation AC 70/7460-1K -- Obstruction
Marking and Lighting on my Light Pollution Awareness Website. Go to
the LiteLynx List and head to Federal Regs in the Index.
http://members.aol.com/ctstarwchr/LiteLynx.htm#federal
White strobes are ONLY required on edifice exceeding 200 feet and
then they are only *required* during the day under certain
conditions.
Dual lighting systems are applicable everywhere in the US where red
blinking lights engage after dark. The best systems are made by
Honeywell Corporation and they have the ability to attenuate the
luminous output according to the ambient lighting conditions,
however, those dual lighting systems with attenuation ability are the
most expensive solutions. Hope it helps!
Clear skies and good seeing,
Keep looking up!
Cliff Haas
Chair Light Pollution Education
Astronomical Society of Greater Hartford
http://members.aol.com/copernicanview
Light Pollution Awareness Website (LiPAW)
http://members.aol.com/ctstarwchr/index.htm
Fight for your right to see stars in the night!
Join IDA Today! http://www.darksky.org
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Message: 11
Date: Fri, 8 Feb 2002 02:09:46 EST
From: ctstarwchr@aol...
Subject: Re: Help with Response to Goveneors Office and Legislators
In a message dated 2/4/02 9:12:23 PM Eastern Standard Time,
windwalker@gci... writes:
> For example, the DOT&PF has installed semi-cutoff light fixtures, which
> produce light above the horizontal, on the Palmer Hay Flats. One reason for
> installing the lighting is to reduce collisions with moose. Full cut-off
> lights would not provide enough light on the flats to reveal moose
> approaching the road.
Hi Tim:
Welcome to the Forum and thanks for providing us with some of the details in
your area of Alaska. Anchorage now reminds me of the lack of foresight in
Providence, Rhode Island. In you area, the impact of such carelessness
probably brings a higher toll due to the total hours of darkness at your
latitude. The process of obtrusive outdoor lighting reform is always going
to be an uphill battle until the pinnacle is reached. After critical mass is
established then the sailing becomes a bit smoother but still needs ongoing
attention and encouragement. ;-)
> Another example involves the lighting we often use along expressways and
> freeways. The "expressway" fixtures allow us to use fewer lights, locate
> them further off the road (which enhances safety and facilitates snow
> removal), and reduces electricity costs by around 30 percent. However,
> because they are oriented diagonally, instead of directly downward, they
> also produce light above the horizontal. Replacing semi-cutoff fixtures
> with full-cutoff fixtures on existing lighting systems can be problematic-in
> many cases, light uniformity would drop below our safety standards.
With those turnpike floods more than HALF of the light is wasted and provides
no benefits whatsoever!!! From responses you have received so far, you
obviously know it is imperative to always remain patient and civil when
negotiating with government officials and government agencies like the DOT
regardless of how ridiculous the objections may be. I have heard many
interesting justifications for using obtrusive lighting, and my apologies,
but this moose story is the most amusing one yet.
I once read a DOT report about Alaskan roadway lighting that mentioned the
FCO fixtures suffer much less vandalism than semi-cutoff lighting does.
Sorry I cannot remember where I found that reference because it was several
years ago. It may have been in the State DOTs that use FCO lighting IDA
information sheet that I passed to the Forum a while back. It is in the best
interest of the public to meet several goals with any civil project
(including lighting): improving safety, reducing operating and maintenance
costs, and providing a good long lasting value for the dollars spent. Good
lighting (if needed) achieves all of them.
An avenue you might try exploring is the Design and Engineering Services (D&
ES) department if you haven't already. They have a roadway beautification
program in effect and glaring lights certainly detract from the aesthetics of
any roadway as well as reduce driver and passenger safety. I'm sure the
moose don't care one way or the other. Fencing makes more sense. The
address for D&ES is:
Anchorage District 279-5582
2221 E. Northern Lights Blvd., Suite 118
Anchorage, AK 99508-4140
More on highway beautification is available here:
http://www.dot.state.ak.us/stwddes/row/fr_rowhistbody.html
Moose may have been crossing those roads because that area might be on their
established route that likely transcends through countless generations.
Migrating animals tend to follow paths of their ancestors. Moose being
indigenous to your area probably migrate mainly in search of food or mates
more than for any other reason. More information on their habitat and habits
may be available from a number of sources including the Forestry Service,
Fish & Wildlife Conservation Commission, Sierra Club, World Wildlife
Foundation, etc. Learning more about their habits and behaviors may help to
establish logical platforms to present to DOT. My limited experience with
moose indicates they are not phased by anything unless you get too close to a
calf, then they tend to charge in an attempt to drive you away. Rightly so,
because they see us as potential predators and we are.
The Commissioner of Alaska DOT is Joseph L. Perkins. Everything trickles
downhill, so if you can get him in favor of fully shielded lighting chances
are good subordinates will do his bidding and install it. DOT has a standing
body known as the Anchorage Metropolitan Area Transportation Study Committee
(AMATS) that makes recommendations on what currently established roads need
improvement and what new roads need to be built. Perhaps discovering who the
Chairman is might help with your negotiations. Network with as many people
as possible, letting them know they are the experts and you are just looking
for their help. Introduce your government representatives' letters to them
also if their responses favor your position. Leave no stone unturned so to
speak.
When speaking with AMATS or D&ES, try to discover what lighting standards
they are adhering to, whether it is AASHTO or IESNA RP-8-00. Also try to
discover what *design method* is used (i.e., illuminance, luminance, or small
target visibility). Let them know the glare makes it very difficult for you
to see if that is true. Improving visual acuity at night is the ONLY logical
reason to install outdoor lighting, and if glare reduces that mission goal
then a rethink of the design logic may be appropriate to consider.
A LOT of roadwork is scheduled for the greater Anchorage area over the next
2-3 years and much of it includes new lighting. Whether it will be good
lighting or glaring lighting is yet to be discovered. Nothing in
documentation I found indicated what would be used for these projects. A
report detailing the work including an estimated budget expenditure is
available on the DOT website at:
http://www.dot.state.ak.us/stwdplng/stip/01_03stip/amendments/01am5stip.pdf
If operating like the DOT in Connecticut, roadway improvement plans are
usually contracted out to private engineering firms rather than detailed in
house. The DOT issues a design criteria with numerous aspects that must meet
compliance. However, the *type* of roadway lighting has never appeared in
any projects that I have been directly involved in developing. That may be
different since October 1, 2001, when the new FCO law went into affect here
in Connecticut. ConnDOT prefers FCO for all new projects. I've lost count
at around 400 fully shielded luminaires when a mere 3 years ago there were
only 8 to be found in over 350 miles of state roads. Each new one discovered
adds more excitement and appreciation.
You might find the Caltrans and Washington DOT lighting manuals to be a help
because both states use fully shielded lighting in their design criteria AND
both states have moose indigenous to their areas as well. ;-) I don't
believe the moose are any less intelligent in Alaska than they are in
California or Washington, do you? We've had moose sightings in CT and use
FCO lights also. You will find both manual references on my LiteLynx List at
the Light Pollution Awareness Website in the Laws section:
http://members.aol.com/ctstarwchr/LiteLynx.htm#laws
Alaska has an intriguing project called ITS, which stands for Intelligent
Transportation Systems. Maybe approaching someone there could help provide
additional insight. Few things could be more intelligent than reducing glare
as much as possible on a roadway lighting system because it improves safety
and reduces negative impacts to the surrounding environment. ITS is located
at:
http://www.alaskaits.com/
The main AK-DOT website is located on the Internet at:
http://www.dot.state.ak.us/
Good luck and keep up the great work! I hope this helps!
Clear skies and good seeing,
Keep looking up!
Cliff Haas
Chair Light Pollution Education
Astronomical Society of Greater Hartford
http://members.aol.com/copernicanview
Light Pollution Awareness Website (LiPAW)
http://members.aol.com/ctstarwchr/index.htm
Fight for your right to see stars in the night!
Join IDA Today! http://www.darksky.org
[Non-text portions of this message have been removed]
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Message: 12
Date: Fri, 8 Feb 2002 11:29:33 +0100
From: "Pierantonio Cinzano" <info@inquinamentoluminoso...>
Subject: R: R: A few things we should know about light pollution!
<However, from the data I have in hand, I have been unable to demonstrate
that
<the calculation of Remande (2000) are wrong. This bother me since I
expected
<more difference but essentialy his result even corrected for the angular
effects
<still facour semi-cuttof optics? Maybe, I made a error in my calculation
<somewhere.
A semi-cut-off fixture (e.g. prismatic glass) can be made with an emission
of zero candles per kilolumen above the horizon.
So far you do not see them because (1) the cited argument is an excuse of
lighting engineers to avoid limits of zero upward emission in Bills and (2)
a good flat-glass fixture allows to light very well so that they are not
necessary.
Here in Italy with flat glasses we arrive, with good uniformity, to a ratio
of 4 between height of the pole and distance of the fixtures, whereas
existing installations statistically are under 3 (usually manifacturers like
to sell as much fixtures as possible).
Lighting engineers usually confuse definitions of CIE cut-off and CIE
semi-cut-off with the fixtures that we need: we need fixtures with no
emission above horizon and any emission below horizon.
I understand that environmentalists ask for limits even at lower angles,
because they limit the quantity of light going outside the road surface.
However so far a limit to the upward emission at 80 degrees was not included
in any law in Italy because it is really quite penalizing unless you make
specific fixtures. It is possible that in few years the requests here will
turn to zero at 80 degrees when environmentalist will have been able to
press manifacturers to make fixtures with 0cd/klm over 80deg and a strong
emission just below.
However if in your country light polluters claim that they cannot limit the
flux going upward, take the chance and ask for the only remaining
possibility: limits on the light installations! We proposed here to limit to
2% the yearly growth rate of the light flux installed in any town (public
and private). This can be very useful to limit light pollution growth rate,
actually at 7%-10%.
Pierantonio
-------------------------------------------------------------------------
PIERANTONIO CINZANO
International Dark-Sky Association - Italia
Direttore Scientifico
e-mail: cinzano@inquinamentoluminoso...
web: http://www.inquinamentoluminoso.it
------------------------------------------------------------------------
-----Messaggio originale-----
Da: Yvan Dutil [mailto:yvan.dutil@sympatico...]
Inviato: giovedì 7 febbraio 2002 3.36
A: DarkSky-list@yahoogroups...
Oggetto: Re: R: [DSLF] A few things we should know about light
pollution!
Pierantonio Cinzano a écrit :
> Dear Ivan,
>
> it is good that a paper make clear that a lumen of light spilled near the
> horizon pollute about three times than the same lumen diffused on the
> asphalt.
Yes, I was happy to see than Jan Hollan got similar result with his own
program.
> In countries like Europe where the CIE-C2 alphalt with a smaller
> albedo is used extensively, you might find even greater factors.
Good comment. I have first plan to used the real BRDF of asphalt
unfortunately
the form used by the CIE neglected the two angles that are to most inportant
for light pollution calculation. I would be very happy if someone could find
the original data at the base of the CIE definition and just process them in
table not optimized for road lighting application but for astronomy. As you
have mention in a couple of paper, there is a specular component in the
reflected light. Even witout knowing the real illumination function of lamp
it is very likely this will increase push more light near the zenith than a
lambertian
reflection. The would mean that we overestiamet the light pollution produce
be the reflection.
>
> Your paper looks very interesting and I will be happy to read it. Nice
work!
You havent read yet for two reasons: it is not yet finish and I estimate
there
is
something like 50% of chance that you will be the referee.
> However, assuming that I understood well your resume, I do not agree with
> your final conclusions. It seems to me that you missed two important
points
> commenting about full cut-off.
>
> You wrote:
> <If we used a standard albedo of 15% for the
> <pavement, it can be shown that the reflected light will dominate the
> <pollution budget if the light emitted directly above the horizon does not
> <exceed 5.5%! This would means that simple cut-off optics would produce
> <less light pollution since they only emit 2% of their light above
horizon.
>
> If we want minimizing light pollution, the pollution produced by light
> emitted directly above the horizon must be very small or negligible in
> respect to the pollution due to reflexion by lighted surface (which is
> necessary to the lighting process). If they are equal for a fixture with
an
> upward flux of 5.5% and if we want reduce the direct pollution at least at
> 1/10 of the reflected pollution, then we need fixtures emitting less than
> 0.55% of upward flux. This means that semi-cut-off fixtures are ruled out
> and you need full cut off.
>
I think it should be 1/10 of 15% in this case about (1.5%). Anyway, cut-off
optics are unlikely to achived that performance. I think that Duco Schreuder
set up at 2% the error on measurement of ULOR from a lamp. Also as I
pointed out mis-align optics will have larger ULOR than stated from the lab
condition. I recentely read a paper that claim the typical mis-aligment is
abour
+-5 degres. This translate in many percent of error in the ULOR. By the way,
is anyone have the official definition for CO, FCO and SCO? They seam to
be conflicting information.
>
> Moreover take into account that it is important not only the "total
> pollution budget" but also the ratio direct versus reflected light at
> different elevation angles.
>
> As the cited paper Cinzano-Diaz Castro showed, the emission at small
> elevations (under 45 degrees) is responsible for almost all the artificial
> sky brightness at zenith outside few kilometers from the sources
> (http://debora.pd.astro.it/cinzano/papers.html). This means that small
> angles emission is a main source of the artificial brightness in the
> country, in astronomical sites outside cities, and sometime also inside
> towns when they are located in densely populated areas.
I have hesited before going for the total light pollution as an indicator.
The key argument that convinced me is that most of the diffused
light lands far from the emitting source. In consequence, the total light
pollution is strongly dominated by the light emitted at low angles. The
other argument is that in most develloped regions the density of population
is such that there is almost always a light source within 5-10 km putting
more weight on high angles in not such a bad thing. The last point is that
I have sacrified the capability to calculate the variation with the distance
in order to simplify the calculation. Anyway, I have not done yet the
comparison between my model and your result for far sources they may
not differ that much after all.
>
> At small elevations the Lambertian emission from surfaces is very small so
> the pollution is due almost completely to direct light from fixtures.
> Minimizing direct pollution in respect to reflected pollution at small
> angles requires limits much smaller than the 0.5% cited above. You
> necessarily need very good full-cut-off fixtures.
My calculation for lambertian surface take account of this effect.
>
> The demonstrations by light engineers that "with less stringent optical
> cutoff, the poles can be more spaced for a same uniformity and the overall
> fraction of light that goes up, including the ground reflection, can be
> reduce by up to 20%" are wrong (or misunderstood)for this and for many
other
> reasons, some of which I explained clearly at the CIE TC4-21 meeting in
> Athens. Probably at New York nobody sufficiently expert to demolish the
> wrong thesis of light polluters has been consulted by politicians. In any
> case it looks like the Governor was in touch with them.
I must say that this is a VERY comment idea in the lighting industry. Even
people from Lumec-Schréder in Québec, who are very against light
pollution put this information in their information sheet. That's why it is
so
important to adresse this issue.
However, from the data I have in hand, I have been unable to demonstrate
that
the calculation of Remande (2000) are wrong. This bother me since I expected
more difference but essentialy his result even corrected for the angular
effects
still facour semi-cuttof optics? Maybe, I made a error in my calculation
somewhere.
>
> The point is that you must minimize not only the total pollution, which is
> an integrated parameter, but also this ratio at any angle. In fact the
> Lumbardy Law in Italy does not limit the upward flux ratio, which is an
> integrated quantity, but it limit the upward intensity per unit flux
(which
> depends on the angle) at any angle over the horizon. And there are no
limits
> at all under the horizon.
>
> Cheers,
>
> Pierantonio
>
> ------------------------------------------------------------------
> PIERANTONIO CINZANO
> Istituto di Scienza e Tecnologia dell'Inquinamento Luminoso - ISTIL
> Light Pollution Science and Technology Institute
> e-mail: cinzano@inquinamentoluminoso...
> cinzano@lightpollution...
> web: http://www.pd.astro.it/cinzano/
> http://www.inquinamentoluminoso.it
> http://www.lightpollution.it/dmsp/
> http://www.istil.it
> ------------------------------------------------------------------
> -------------------------------------------------------------------------
> PIERANTONIO CINZANO
> International Dark-Sky Association - Italia
> Direttore Scientifico
> e-mail: cinzano@inquinamentoluminoso...
> web: http://www.inquinamentoluminoso.it
> ------------------------------------------------------------------------
>
> -----Messaggio originale-----
> Da: Yvan Dutil [mailto:yvan.dutil@sympatico...]
> Inviato: mercoledì 6 febbraio 2002 2.06
> A: DarkSky-list@yahoogroups...
> Oggetto: [DSLF] A few things we should know about light pollution!
>
> This a text I have prepare for the next dark-sky newsletter.
Unfortunately,
> due to a lack of place,
> we will have to wait up to next edition to have it publish. Meanwhile, I
> will
> have probably publish
> my research paper in PASP. By the way, I am open to any comment.
>
> Yvan Dutil
>
> --------------------------------------------------------------------------
--
> ----------
>
> Recently, two major legislations against light pollution have been
rejected.
> One in the New York state, the other in the Czech Republic, One of the
> reasons invoked was lack of scientific justification for full cut-off
lamp.
> Arguments invoked by astronomers (light above the horizon=pollution)
> backfired in face of analysis done by lighting engineers demonstrating
that
> with less stringent optical cutoff, the poles can be more spaced for a
same
> uniformity and the overall fraction of light that goes up, including the
> ground reflection, can be reduce by up to 20% (Remande 2000).
Unfortunately,
> these two conflicting conclusions are based on simplistic model of the
light
> pollution. Our understanding of the light pollution must improve otherwise
> the same scenario will repeat again.
>
> Common sense is that up-going light equals light pollution. The classical
> example is an old fashion lamp that emits directly 35% of the light up,
65%
> down of which 10% is reflected up. Overall, 45% of the light ends up
> illuminating the sky. Then with full cut-off optics, the direct emitted
> light
> goes down to 0%, and only the light reflected on the ground goes up, 10%.
In
> consequence, we would expect a spectacular 88% in reduction of the overall
> pollution. Lighting engineer got even further, by following the
engineering
> norms and applying their model for road illumination, they came down to
the
> conclusion that light pollution can be minimized of you use semi-cutoff
> optics, which allows a few percents of light to spill above the horizon.
>
> Unfortunately, this model does not take account of a very simple fact:
light
> emitted at low angle is more polluting that light emitted at the vertical.
> Simply, there is more air in the direction of the horizon than at the
> zenith,
> which provide more chance for a photon to get diffused. Don’t forget, that
> in
> essence light pollution is not a problem of light going up but a problem
of
> light that was going up but got diffused on the ground. In consequence, it
> has been shown up by Pierantiono Cinzano & Francisco Javier Diaz Castro,
> that
> most of the light pollution is produce by light emitted at angle below 10
> degrees above the horizon. Unfortunately, the results of this key paper
are
> presented in a form that renders them impractical for engineering
practice.
>
> In order, to address this issue I have develop a simple model of
atmospheric
> diffusion (Dutil 2002). It is essentially the same model as the one
develop
> by Garstang and use recently by Cinzano et al. to produce their world
atlas
> of light pollution. With some simplifications that ease the calculation
but
> have little impact on the final result.
>
> For typical atmospheric condition, the light pollution efficiency peaks at
4
> degrees above the horizon at a value 5.85 times higher than at zenith.
> However order to evaluate the real impact of the light pollution, we have
to
> sum the contribution of every angles. I have examined three typical
emission
> functions: uniform over 10 first degrees above horizon (spilled light from
a
> good lamp), lambertian (like a reflection on pavement) and uniform (like
the
> emission of a globe). The pollution coefficients for each distribution are
> respectively 0.7950, 0.2902 and 0.4206. From these numbers we can deduce
> that a lumen of light spilled near the horizon pollution 2.74 more than
the
> same lumen diffused on the asphalt, and 1.89 times more that if it was
> emitted by an infamous globe! Readers have to be advised that this result
> have not been peer reviewed yet and in consequence should be use with
great
> care.
>
> What does this means in practice? If we used a standard albedo of 15% for
> the
> pavement, it can be shown that the reflected light will dominate the
> pollution budget if the light emitted directly above the horizon does not
> exceed 5.5%! Taken at face value this would means that lighting engineers
> are
> right and that simple cut-off optics would produce less light pollution
> since
> the only emit 2% of their light above horizon. If we recalculate the
> previous
> example with those number, we get: 35%+10%/2.74=38.65% vs 10%/2.74=3.65%.
As
> we can see, the real reduction of light pollution is 90.6% instead of 88%
as
> we have previously calculated.
>
> Is this the end of the full cut-off lamp? Nothing is less sure. First, we
> need to take account of the real amount of light spilled by lamp. Lamps
are
> rarely exactly level and this inevitably increasing the light loss. This
> factor alone is enough to favor full cut-off optics. Second, the claims
of
> engineers are based on a requirement of illumination uniformity. Real
night
> vision is more complex and rigorous modeling with probably end up with a
> different result, especially if glare is taken into account.
>
> Do not forget that better lighting practice is our ultimate goal. Once the
> physics is well understood, optimization is easy.
>
> Reference:
>
> Cinzano, P., Diaz Castro, F. J., 2000, Mem. Soc. Astro. It., 71, 251
> Cinzano, P., Falchi, F., & Elvidge, C. D. 2001, Monthly Notices of the
Royal
> Astronomical Society, 328, 689
> Dutil, Y., to be submitted to Publication of the Astronomical Society of
the
> Pacific
> Garstang, R. H. 1986, Publication of the Astronomical Society of the
> Pacific,
> 98, 364
> Garstang, R. H. 1989, Publication of the Astronomical Society of the
> Pacific,
> 101, 306
> Garstang, R.H. 1991, Publication of the Astronomical Society of the
Pacific,
> 103, 1109
> Remande, C., 2001, in Preserving the Astronomical Sky, IAU Symposium, Vol.
> 196, R. J. Cohen and W. T. Sullivan, III, eds.
>
> _________________________________________________
> To subscribe to the DarkSky List Forum send email
> to: DarkSky-list-subscribe@yahoogroups...
>
> Help save your town from obtrusive lighting --
> invite your planning and zoning department to
> join us! Ask them to visit the IDA website at
> http://www.darksky.org today!
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
> _________________________________________________
> To subscribe to the DarkSky List Forum send email
> to: DarkSky-list-subscribe@yahoogroups...
>
> Help save your town from obtrusive lighting --
> invite your planning and zoning department to
> join us! Ask them to visit the IDA website at
> http://www.darksky.org today!
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
_________________________________________________
To subscribe to the DarkSky List Forum send email
to: DarkSky-list-subscribe@yahoogroups...
Help save your town from obtrusive lighting --
invite your planning and zoning department to
join us! Ask them to visit the IDA website at
http://www.darksky.org today!
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
________________________________________________________________________
________________________________________________________________________
Message: 13
Date: Fri, 8 Feb 2002 12:33:22 +0000
From: chris@tunnah....uk
Subject: Bird Migration by Constellations - what if they can't see them??
Have you seen the research by Henrik Mouritsen and Ole Naesbye Larsen of
Odense University, Denmark? An article appeared in the Independent
newspaper (UK) of 7th Feb. which caught my eye (also written up in
'Journal of Experimental Biology'). They used a planetarium to 'fool'
birds as to their orientation and recorded their movements with surprising
results.
This must indicate that birds can become confused by light
polution....unless they see the stars clearly at different frequencies to
human eyes?
Chris Tunnah
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Message: 14
Date: Fri, 8 Feb 2002 09:37:37 -0500
From: "Peel, Bill D." <BPeel@Lithonia...>
Subject: RE: Re: Lighting cost calculator
Terry, I have always been of the understanding that 'mean lumens' was simply
a metric devised by lamp engrs. to evaluate different lamp designs. It is
the point on the LLD curve where the area under the curve is divided equally
(50% of total lumen-hours). It's interesting to note that a large lighting
installation that is spot relamped monthly (never group relamped) will,
after, several years, converge on an average level defined by mean lumens.
Coincidence?
Bill Peel
Lithonia Lighting
-----Original Message-----
From: Terry McGowan [mailto:lighting@ieee...]
Sent: Thursday, February 07, 2002 5:09 PM
To: DarkSky-list@yahoogroups...
Subject: Re: [DSLF] Re: Lighting cost calculator
I used "mean lumens" and "mean efficacy" in the Advanced Lighting Guidelines
so that the depreciation characteristics of the lamp could be taken into
account when comparing lamps and systems. The mean values aren't meant to be
a design factor unless someone wants to design to mean output over time.
________________________________________________________________________
________________________________________________________________________
Message: 15
Date: Fri, 8 Feb 2002 11:27:44 EST
From: ctstarwchr@aol...
Subject: Re: A few things we should know about light pollution!
In a message dated 2/8/02 5:31:07 AM Eastern Standard Time,
info@inquinamentoluminoso... writes:
> A semi-cut-off fixture (e.g. prismatic glass) can be made with an emission
> of zero candles per kilolumen above the horizon.
>
> So far you do not see them because (1) the cited argument is an excuse of
> lighting engineers to avoid limits of zero upward emission in Bills and (2)
> a good flat-glass fixture allows to light very well so that they are not
> necessary.
>
> Here in Italy with flat glasses we arrive, with good uniformity, to a ratio
> of 4 between height of the pole and distance of the fixtures, whereas
> existing installations statistically are under 3 (usually manufacturers like
> to sell as much fixtures as possible).
Greetings Pierantonio:
Out of curiosity, what is the standard mounting height used for the flat lens
roadway fixtures mounted along your highways in Italy? How much does the
height and spacing differ from that used for the drop lens refractor (i.e.
semi-cutoff) luminaire spacing? A 3:1 ratio to the centerpoint of overlap
seems to be fairly common in the US.
What you said above may indeed be possible, but not through use of any
prismatic lenses that we commonly use today. The technology to achieve this
is nearing 200 years old in the field of optical engineering! A gentleman
named Augustin Jean Fresnel devised a unique refractor in 1822 that
redirected light more efficiently than anything that ever preceded it in the
past. The efficiency Fresnel's discovery brought to lighting has never
improved the coefficient of utilization beyond that point, perhaps because
there was no need to do so, with exception of replacing ultra high
maintenance oil flames with electric lighting in the early 1900s.
I am a fancier of lighthouses that warn mariners of potential coastal dangers
and aid their nocturnal navigation. They originally used the flames of oil
lamps, but most of the flame's light was lost to heat rather than being
distributed into a concentrated beam, even after using a reflector behind the
flame. The Fresnel lens was one of the greatest breakthroughs in the history
of optical physics and was not surpassed until the laser came along.
Testing at the time of that amazing discovery indicated that open flames lost
nearly 97% of their useful light. Even flames with reflectors behind still
lost 83% of their light but a flame placed within a Fresnel lens only lost
17% of its light to the task at hand. This revolutionary breakthrough was
able to take a coefficient of utilization of only 0.03 and brought it to an
astounding 0.83, thus converting the faint flicker of an oil flame into a
useful tool in the form of a definitive beam that was clearly visible well
over twenty miles out to sea! Shortly after that discovery, countries around
the world scrambled to install these revolutionary lenses in lighthouses all
over the place. Many still exist today, but sadly they are dwindling due to
geostationary satellites and GPS systems technology.
I don't suggest for a minute that we start installing Fresnel lenses on light
poles used to illuminate roadways for obvious reasons, but a modified
application of the optical properties Fresnel discovered could indeed bring
us pole spacings approaching 6 mounting heights or more without blasting
people with enormous amounts of glare, while still providing even uniformity
using light sources that consume much less power than they do by today's
standards. Imagine lighting roadways with 35 watts or less, instead of 400
commonly used today? Think of the benefits this would bring to society.
Maybe if engineers working for the luminaire manufacturers did a bit of
research into the history and theory of Fresnel's optics and applied that
newfound knowledge, everybody could have cake and eat it too. ;-) I doubt
if anyone except the utility companies would object to longer pole spacing
and using much less energy to drive a lighting system. Does anyone know how
many watts per square meter an oil flame produces in light emission? I doubt
if it is more than 5 or so.
One of my favorite lighthouses is located at Ponce Inlet in Daytona, Florida.
You can see a first order Fresnel lens similar to the one this lighthouse
used to warn mariners at:
http://www.lighthousegetaway.com/lights/fresnel.html
It is presently illuminated with a 25 watt incandescent bulb at the center
and is literally BLINDING when you step into the beam. The Smithsonian
Institution also has a number of Fresnel lenses of the various orders on
display. A story appeared about them in the August 1999 issue of Smithsonian
Magazine.
http://www.smithsonianmag.si.edu/smithsonian/issues99/aug99/object_aug99.html
Imagine, if you will, a luminaire driven by a low wattage HID source
employing both front and back (house and street side) shielding that uses a
Fresnel lens concept on each side faceing parallel with the direction of
traffic flow. Placing an opaque specular housing shaped in the form of a
shallow parabola above these lenses could easily achieve zero candela
emission above the horizontal plane. Essentially, history suggests this
concept has the potential to put MUCH more light onto the road surface where
today's best designed refractors normally send less than 50% of their usable
light to the task at hand (the road and only the road). Think outside of the
box and lead rather than blindly follow! Food for thought. Please feast
well and bring us better, more efficient products that respect the sky and
benefit the eye!
Clear skies and good seeing,
Keep looking up!
Cliff Haas
Chair Light Pollution Education
Astronomical Society of Greater Hartford
http://members.aol.com/copernicanview
Light Pollution Awareness Website (LiPAW)
http://members.aol.com/ctstarwchr/index.htm
Fight for your right to see stars in the night!
Join IDA Today! http://www.darksky.org
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Message: 16
Date: Fri, 8 Feb 2002 13:45:48 EST
From: ctstarwchr@aol...
Subject: Re: A few things we should know about light pollution!
In a message dated 2/8/02 1:07:51 PM Eastern Standard Time, Paul Lutkevich
(Chair of IESNA Roadway Lighting Committee) writes:
> Cliff,
>
> Be careful with a couple of things in the email. European roads are lit
> more uniformly and to approximately twice the lighting levels of US roads.
> They do use spacing to mounting heights of 3:1 to 4:1. Most US roads use
> 5:1 spacing: mounting heights.
>
> As far as lens technology and approaching 6:1 S:MH ratios I don't think
> that we will avoid blasting people with glare. In fact all high peak
> candela aimed in the direction of a person will cause enormous amounts of
> glare and to compound that a reduced background brightness will make the
> effect of the glare even worse.
>
> I think reflector optics are a better fit and when refractors are used,
> correctly designed and lower lamp wattage are the keys.
>
> Thanks for the history lesson on Fresnel lenses.
>
>
Thank you Paul for sharing your insight and wisdom! What I try to suggest is
taking that old technology and dusting it off a bit for today's applications.
The optimum solution might be found in a flat lens refractor that improves
transmittance along its outer reaches. At those high angles the typical FCO
luminaire lens' glass thickness parallels thickness of atmosphere near the
horizon that spreads skyglow through properties of Rayleigh and MIE
scattering, but consequently, it and the inverse square law also diminishes
maximum candela distribution in the outer reaches as a result.
The eighty degree cutoff is a fair limitation point to effectively reduce
direct glare. More efficiently designed lens prisms with magnification
properties might help to improve the perplexing conditions of reduced
uniformity and provide a more even distribution was my main point. I'm all
for reducing illumination intensity if uniformity and contrast recognition
does not suffer as a result. Good luck in Tucson at the RLC meeting next
month!
Cheers,
Cliff Haas
http://members.aol.com/ctstarwchr
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