[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[DSLF] Digest Number 582
_________________________________________________
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!
------------------------------------------------------------------------
There are 7 messages in this issue.
Topics in this digest:
1. Massachusetts EOEA
From: Mike Hansen <mhansen@einhornresearch...>
2. Re: A few things we should know about light pollution!
From: "David Penasa" <dpenasa@bplw...>
3. Fw: A few things we should know about light pollution!
From: "David Penasa" <dpenasa@bplw...>
4. Re: A few things we should know about light pollution!
From: "David Keith" <keithd@resodance...>
5. Re: Great Lakes Radio Consortium piece on dark skys
From: Scott Griswold <griz@sky...>
6. Re: Fw: Great Lakes Radio Consortium piece on dark skys.
From: "Karolyn Beebe" <keedos@earthlink...>
7. Re: Massachusetts EOEA
From: Barry Johnson <johnsonb@ivwnet...>
________________________________________________________________________
________________________________________________________________________
Message: 1
Date: 14 Feb 2002 07:16:13 -0500
From: Mike Hansen <mhansen@einhornresearch...>
Subject: Massachusetts EOEA
I received a letter from the Massachusetts Executive Office of Environmental Affairs yesterday in response to a request I had made of them. I asked if they might address light pollution as part of their mission. Of course, I sent all the usual information and links.
The Director of Air Policy and Planning replied in part:
"Thank you for bringing the issue of proper nighttime lighting to the attention of the Swift [Governor] Administration. I did not know much about the issue and have been researching it since your letter was referred to me. I . . . have been working on methods to reduce emissions and climate change gases in particular.
"Having more efficient outdoor lighting would be a win-win effort because we could reduce energy use while also having the major benefit of being able to shield the night sky from excess lighting.
"This issue is exactly the type of project that we are seeking for implementation. I have recently been reading about the benefits of full cut off lighting for the purpose of energy savings and I am looking into the use of such fixtures for inclusion in state buildings and state funded projects."
One more person whose eyes have been opened.
--
Mike Hansen
2561 Massachusetts Avenue #1
Cambridge, MA 02140-1020
617-661-6520
________________________________________________________________________
________________________________________________________________________
Message: 2
Date: Thu, 14 Feb 2002 09:46:14 -0700
From: "David Penasa" <dpenasa@bplw...>
Subject: Re: A few things we should know about light pollution!
>Barry Johnson wrote:
> Here are the actual IESNA definitions of Full Cutoff classification:
>
> Notice this difference:
>
> IESNA Lighting Handbook, 9th Edition, p.7-8:
>
> Description of Intensity distribution:
> Full Cutoff A luminaire light distribution where zero candela
intensity
> occurs at an angle of 90 degrees above nadir and at all greater angles
from
> nadir. Additionally, the candela per 1000 lamp lumens does not
numerically
> exceed 100(10%) at a vertical angle of 80 degrees above nadir. This
applies to
> all lateral angles around the luminaire.
>
> IESNA RP-8-2000 American National Standard Practice for Roadway
Lighting, p.6:
>
> Full Cutoff:
> A luminaire light distribution where zero candela intensity occurs at
or above
> an angle of 90 degrees above nadir. Additionally, the candela per
1000 lamp
> lumens does not numerically exceed 100(10 percent) at OR ABOVE [my
capitals] a
> vertical angle of 80 degrees above nadir. This applies to all lateral
angles
> around the luminaire.
>
> So here are two different IESNA definitions of Full Cutoff. One
places a
> maximum candela limitation at 80 degrees while the other places it
at -or above-
> 80 degrees.
>
> When a manufacturer certifies that its luminaire meets the
requirements of the
> Full Cutoff classification, presumably it can choose either definition
> promulgated by The Lighting Authority.
>
>
> Barry Johnson
>
Here is a reply that I received from someone on the IESNA Roadway
Lighting Committee:
----- Original Message -----
From: Doug P
To: 'David Penasa' <dpenasa@bplw...>
Sent: Thursday, February 14, 2002 9:27 AM
Subject: RE: [DSLF] A few things we should know about light
pollutionDavid,
This would get into the realm of work by Testing Procedures Committee or
"the TPC". They script out the exact procedure for measurement and
reporting formats for the Photometry Labs in North America.
The Handbook definition might allow a value to slip by that is higher
than
allowed in the 81 to 89 degree area, but I can't imagine a product that
would produce this anomaly. Understand that if you have a fixture that
cuts
off to NOTHING at 90 degrees AND cuts of to 10% of the lumen value at 80
degrees, you play hell getting an increasing value between 80 and 90!
It
just doesn't happen.
In fact, it's infrequent that a product "Fails" at 80 and has zero at 90
degrees, but I've seen them . . . a flat glass "semi-cutoff" fixture.
And
we have one.
But I think the SYSTEM fails US when it worries NOT what happens below
80
degrees . . . as it's useless to predict light trespass problems. You
have
to go into the tabulated candlepower page of the test report to
determine if
the house-side (or any other offending side) attenuates candlepower for
the
geometry of the site.
I trust that these slightly different definitions will be rectified as
the
documents are revised. This is truly non-consequential.
doug
________________________________________________________________________
________________________________________________________________________
Message: 3
Date: Thu, 14 Feb 2002 09:48:38 -0700
From: "David Penasa" <dpenasa@bplw...>
Subject: Fw: A few things we should know about light pollution!
And, another reply from an IESNA Roadway Lighting Committee person on
the ongoing topic:
----- Original Message -----
From: Doug P
To: 'David Penasa' <dpenasa@bplw...>
Sent: Thursday, February 14, 2002 9:46 AM
Subject: RE: R: [DSLF] A few things we should know about light
pollution!
David,
It's widely know among optics designers that a clear (unprism'd) sag
lens
allows more transmission and less reflection of high angle light. It
basically changes the angle between the light rays and the medium to a
lesser angle. The same laws of reflection/transmission apply, it's just
that the angle is reduced. So in order to get maximum spacing between
fixtures, say a 6X6 spacing-to-mounting-height ratio, your critical beam
is
at 45 degrees horizontal and something close to 75 degrees vertical. In
order to still meet cutoff, you have to "plan" your beam to "max-out" at
something lower than 75, be decreasing at 75, and be within cutoff
limits at
80. But the reflected light exiting the fixture at 75 degrees is
reduced by
a huge amount because most of the light reflects back into the fixture
off
the first surface of the lens. We often speak of these beams being "in
the
fuzz" because you cannot very well predict how much is actually going to
come out.
Now, I personally believe that IDA is doing themselves a disservice by
requireing flat lenses. Photometric labs in the USA DO NOT give Full
Cutoff
designations to anything but flat lenses. I don't care what the Italian
gentlemen says.
So now you've got Full Cutoff fixtures that only perform well on a 5X5
SMH
and the lighting designer uses more of them to achieve proper
uniformity.
More fixtures reflecting light off the ground and into the heavens.
Another side story for WHITE light. Did you know that Asphalt and
Concrete
reflect more HPS light than it does Metal halide light? Dr. Adrian
presented this research to the Roadway committee last year.
doug
________________________________________________________________________
________________________________________________________________________
Message: 4
Date: Thu, 14 Feb 2002 15:00:23 -0700
From: "David Keith" <keithd@resodance...>
Subject: Re: A few things we should know about light pollution!
As part of my work with the IESNA Roadway Lighting Committee, I provided the
same text for these definitions for both documents. The "difference" is
completely the "work" of the editors of the Handbook. The RLC was the
source of the initial classification definitions and the revised definitions
and continues to refine them.
In historical and practical terms, luminaire intensity typically decreases
as elevation increases, in which case the definitions are "effectively
equal" - even if they could produce different results for some (theoretical)
distributions.
Also, the term "full cutoff" has MANY other definitions - I have seen at
least ten that differ significantly. Apparently many jurisdictions feel
that they must rewrite definitions to suit themselves - regardless of
technical accuracy or any confusion created. This is part of the problem
with such "component" approaches - definitions get "tweaked" and become ...
less useful.
David Keith
> David Keith wrote:
>
{editted}
> >
> > 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
>
> Here are the actual IESNA definitions of Full Cutoff classification:
>
> Notice this difference:
>
> IESNA Lighting Handbook, 9th Edition, p.7-8:
>
> Description of Intensity distribution:
> Full Cutoff A luminaire light distribution where zero candela intensity
> occurs at an angle of 90 degrees above nadir and at all greater angles
from
> nadir. Additionally, the candela per 1000 lamp lumens does not
numerically
> exceed 100(10%) at a vertical angle of 80 degrees above nadir. This
applies to
> all lateral angles around the luminaire.
>
> IESNA RP-8-2000 American National Standard Practice for Roadway Lighting,
p.6:
>
> Full Cutoff:
> A luminaire light distribution where zero candela intensity occurs at or
above
> an angle of 90 degrees above nadir. Additionally, the candela per 1000
lamp
> lumens does not numerically exceed 100(10 percent) at OR ABOVE [my
capitals] a
> vertical angle of 80 degrees above nadir. This applies to all lateral
angles
> around the luminaire.
>
> So here are two different IESNA definitions of Full Cutoff. One places a
> maximum candela limitation at 80 degrees while the other places it at -or
above-
> 80 degrees.
>
> When a manufacturer certifies that its luminaire meets the requirements of
the
> Full Cutoff classification, presumably it can choose either definition
> promulgated by The Lighting Authority.
>
>
> Barry Johnson
________________________________________________________________________
________________________________________________________________________
Message: 5
Date: Thu, 14 Feb 2002 20:16:12 -0500
From: Scott Griswold <griz@sky...>
Subject: Re: Great Lakes Radio Consortium piece on dark skys
This has to be one of the best written pieces I have ever heard. It
covers nearly every aspect of the various problems resulting from
Light pollution.
Here is a link to a another story on the site...Another excellent
account...
http://www.glrc.org/story.php3?story_id=1411
Peace & Dark Skies,
Scott Griswold
> From: "Karolyn Beebe" <keedos@earthlink...>
> Sent: Wednesday, February 13, 2002 11:20 AM
> Subject: Great Lakes Radio Consortium piece on dark skys.
>
>
>> Please see:
>> http://www.glrc.org/
________________________________________________________________________
________________________________________________________________________
Message: 6
Date: Thu, 14 Feb 2002 19:25:52 -0600
From: "Karolyn Beebe" <keedos@earthlink...>
Subject: Re: Fw: Great Lakes Radio Consortium piece on dark skys.
> > Please see:
> > http://www.glrc.org/
FYI - Hope the reports: "Apperciating the Night
Sky" & "Women in Astronomy" hit lots of airways.
What friends seem to like most is the commentary:
"What's good about the night" which is linked in
the right column. -kb
________________________________________________________________________
________________________________________________________________________
Message: 7
Date: Fri, 15 Feb 2002 00:12:46 -0500
From: Barry Johnson <johnsonb@ivwnet...>
Subject: Re: Massachusetts EOEA
Well done , Mike.
Regards,
Barry Johnson
Mike Hansen wrote:
> I received a letter from the Massachusetts Executive Office of Environmental Affairs yesterday in response to a request I had made of them. I asked if they might address light pollution as part of their mission. Of course, I sent all the usual information and links.
>
> The Director of Air Policy and Planning replied in part:
>
> "Thank you for bringing the issue of proper nighttime lighting to the attention of the Swift [Governor] Administration. I did not know much about the issue and have been researching it since your letter was referred to me. I . . . have been working on methods to reduce emissions and climate change gases in particular.
>
> "Having more efficient outdoor lighting would be a win-win effort because we could reduce energy use while also having the major benefit of being able to shield the night sky from excess lighting.
>
> "This issue is exactly the type of project that we are seeking for implementation. I have recently been reading about the benefits of full cut off lighting for the purpose of energy savings and I am looking into the use of such fixtures for inclusion in state buildings and state funded projects."
>
> One more person whose eyes have been opened.
> --
> Mike Hansen
> 2561 Massachusetts Avenue #1
> Cambridge, MA 02140-1020
> 617-661-6520
>
> _________________________________________________
> 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/
________________________________________________________________________
________________________________________________________________________
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/