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[DSLF] Digest Number 581
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There are 6 messages in this issue.
Topics in this digest:
1. DOT websites
From: "David Penasa" <dpenasa@bplw...>
2. Fw: Great Lakes Radio Consortium piece on dark skys.
From: "Karolyn Beebe" <keedos@earthlink...>
3. STN: INTERNET-BASED TELESCOPE FOR HIGH SCHOOL STUDENTS GOES LIVE!
From: Hstinst@aol...
4. RE: R: R: R: A few things we should know about light pollution!
From: "Pierantonio Cinzano" <info@inquinamentoluminoso...>
5. Re: A few things we should know about light pollution!
From: Barry Johnson <johnsonb@ivwnet...>
6. Re: R: R: R: A few things we should know about light pollution!
From: Yvan Dutil <yvan.dutil@sympatico...>
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Message: 1
Date: Wed, 13 Feb 2002 09:51:04 -0700
From: "David Penasa" <dpenasa@bplw...>
Subject: DOT websites
http://www.constructionweblinks.com/Industry_Topics/Specifications__Tech
nical_Data/Specifications_and_Technical_D/Particular_Owners__Specificati
/particular_owners__specificati.html
(link may wrap - be sure to paste all portions of link into your web
browser)
Construction WebLinks - Listing of State DOT websites, among other
Owners. May include roadway lighting standards for some states.
David
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Message: 2
Date: Wed, 13 Feb 2002 12:25:15 -0600
From: "Karolyn Beebe" <keedos@earthlink...>
Subject: Fw: Great Lakes Radio Consortium piece on dark skys.
a short, sweet audio : ) -kb
Sent: Wednesday, February 13, 2002 11:20 AM
Subject: Great Lakes Radio Consortium piece on dark skys.
> Please see:
> http://www.glrc.org/
>
> ***************************************************
> David S. Liebl
> University of Wisconsin
> Solid & Hazardous Waste Education Center
> Room 311 432 N. Lake Street
> Madison, WI 53706-1498
> 608/265-2360 FAX/263-3160 <liebl@epd....wisc.edu>
> *****************************************************
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Message: 3
Date: Wed, 13 Feb 2002 16:05:13 EST
From: Hstinst@aol...
Subject: STN: INTERNET-BASED TELESCOPE FOR HIGH SCHOOL STUDENTS GOES LIVE!
FOR IMMEDIATE RELEASE 2/13/02
Contact: STNmedia@hotmail..., (610) 926-6638
INTERNET-BASED TELESCOPE FOR HIGH SCHOOL STUDENTS GOES LIVE!
No longer does a high school student trying to prepare an assignment or
science fair project have to copy pictures from a book to illustrate ideas
about astronomical objects. Now they can dial up an on-line telescope using
the Internet and get real-time pictures of what they want, almost independent
of weather and the school's budget for expensive optics. This is arguably
the first telescope controllable over the Internet that is not located at a
multi-million dollar observatory complex, and is available exclusively for
high school student's use.
The Student Telescope Network (STN) is a collaborative project to enable
high school students interested in astronomical observing, to access a
telescope with digital camera in a remote dark location via the Internet,
and to pursue basic observational research. High school students and
their science teachers are invited to look at website
www.youthinastronomy.org for information about the pilot project, and how to
participate!
STN is made possible by the cooperation of the Youth Activities Committee
of the Astronomical League, the University of Denver Astronomy Program,
New Mexico Skies, and Software Bisque. Ryan Hannahoe, Chairman of the
Youth Activities Committee (www.youthinastronomy.org), himself a high
school student at Schuylkill Valley High School in Leesport, Pennsylvania,
says, "I personally
like the real-time, live control of the Internet telescope. No more waiting
in line at an observatory to pursue my research observations." Hannahoe also
says, "Command the telescope where to go and how long of an exposure to take
and within seconds you have your image. It's just that easy to use and to
learn. The best part about it is you need NO software to run the telescope,
just an Internet connection and it is free to use and very user friendly!"
"Talk with high school students, and you will quickly learn what holds their
interest: live, real-time, hands-on, student driven activity. Observational
astronomy easily fits these expectations" says Dr. Robert Stencel, professor
of Astronomy at the University of Denver."
The New Mexico Skies Observatory in southern New Mexico hosts the on-line
telescope. Software Bisque of Golden, Colorado invented the telescope control
hardware and software that makes this revolutionary observing
possible. Astronomers at the University of Denver are playing the role of
coordinator and scheduler during the remainder of the current school
year. STN is happy to acknowledge sponsorship by the Toyota Foundation's
Institute for Connecting Science Research to the Classroom.
[Non-text portions of this message have been removed]
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Message: 4
Date: Thu, 14 Feb 2002 04:16:04 +0100
From: "Pierantonio Cinzano" <info@inquinamentoluminoso...>
Subject: RE: R: R: R: A few things we should know about light pollution!
<I have discuss with lighting engineer about this issue. As I unserstand it,
they
<can actually achieved the correct illumination on the ground with flat lens
but
<the internal loss in the lamp are increased. This is caused by a
augmentation
<of the reflection on surface at grazing angle. Curved lens dimish these
effect.
1) You do not need flat glass to obtain a fixture with zero emission at 90
degrees and above. You need only that the body of the fixture screens the
upward light. So this problem has no interest for us.
2) By the way, did you ever checked in common road fixtures the angle of
incidence of light rays coming from the lamp (sometime elissoidal, i.e.
large) AND from the reflector on the curved glass of the kind that usually
you find? The smaller loss due to curved glass in respect of flat glass
works only for a theoretical pointed source without reflector.
It works at best on the paper which light polluters typically exibit when
they try to obtain larger limits during a discussion for a Bill. It work
less well when applyed to a fixture where the source of rays is not pointed
but is a system lamp+reflector.
Moreover did you noticed that some curved glasses are really squared with
angles very reflective?
Did you noticed that a great part of the surface of some curved glasses
makes an angle with the rays coming from the lamp which is greater than the
angle with a flat glass?
Do you belive to all things that lighting engineers say you? Good luck!!
Pierantonio
------------------------------------------------------------------
PIERANTONIO CINZANO
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
------------------------------------------------------------------
-----Messaggio originale-----
Da: Yvan Dutil [mailto:yvan.dutil@sympatico...]
Inviato: sabato 9 febbraio 2002 17.35
A: DarkSky-list@yahoogroups...
Cc: International Dark-Sky Association
Oggetto: Re: R: R: [DSLF] A few things we should know about light
pollution!
Pierantonio Cinzano a écrit :
> <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.
>
I have discuss with lighting engineer about this issue. As I unserstand it,
they
can actually achieved the correct illumination on the ground with flat lens
but
the internal loss in the lamp are incraese. This is caused by a augmentation
of the reflection on surface at grazing angle. Curved lens dimish these
effect.
Yvan Dutil
_________________________________________________
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: 5
Date: Wed, 13 Feb 2002 23:33:05 -0500
From: Barry Johnson <johnsonb@ivwnet...>
Subject: Re: A few things we should know about light pollution!
David Keith wrote:
> 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
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
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Message: 6
Date: Thu, 14 Feb 2002 00:02:11 -0500
From: Yvan Dutil <yvan.dutil@sympatico...>
Subject: Re: R: R: R: A few things we should know about light pollution!
Pierantonio Cinzano a écrit :
> <I have discuss with lighting engineer about this issue. As I unserstand it,
> they
> <can actually achieved the correct illumination on the ground with flat lens
> but
> <the internal loss in the lamp are increased. This is caused by a
> augmentation
> <of the reflection on surface at grazing angle. Curved lens dimish these
> effect.
>
> 1) You do not need flat glass to obtain a fixture with zero emission at 90
> degrees and above. You need only that the body of the fixture screens the
> upward light. So this problem has no interest for us.
I agree with you. However, putting a shield is often not an option due to
mecanical constrains (wind, ice load). If the feature is include from scratch
in the design, it may have a lesser impact.
> 2) By the way, did you ever checked in common road fixtures the angle of
> incidence of light rays coming from the lamp (sometime elissoidal, i.e.
> large) AND from the reflector on the curved glass of the kind that usually
> you find? The smaller loss due to curved glass in respect of flat glass
> works only for a theoretical pointed source without reflector.
> It works at best on the paper which light polluters typically exibit when
they try to obtain larger limits during a discussion for a Bill. It work
> less well when applyed to a fixture where the source of rays is not pointed
> but is a system lamp+reflector.
>
> Moreover did you noticed that some curved glasses are really squared with
> angles very reflective?
> Did you noticed that a great part of the surface of some curved glasses
> makes an angle with the rays coming from the lamp which is greater than the
> angle with a flat glass?
I really dont see how this can happen. Curved surface will have smaller incident
angles than a flat surface. This is certain for direct rays emitted by the lamp
and
this is true in average also for reflected rays comings from the reflector.
> Do you belive to all things that lighting engineers say you? Good luck!!
>
> Pierantonio
I must say that I do not agree with you on this issue. With or without
reflector,
a lamp fixture has to emit significant light and angle up to 75 degres from
the vertical. This means angle of 15 degree to an horizonthal surface. At this
angle you loose about 25% by reflection on each interface air-glass. If using
a curved surface you reduce this angle to 60 degres the loss goes down to
~10% per interface. That where the 20% gain in radiometric efficiency comes
from. This effect will happen what ever is your optical design however is
more critical for flatter lens system. I agree with you that this argument does
not work for the old cobra lens system with are much to curved anyway. But
it does apply to modern high efficiency equipment.
Specificaly, this analysis as been done on a lamp that was the most efficient
(Lumen per watts) in the world a few years ago. It leaked a little amount of
energy above horizon however. And we asked for a zero emission above horizon.
This could be achived simply by replacing the curved bottom glass by a flat
glass,
which for us was more practical than having shield installed.
However, this resulted in a loss of 20% in optical efficiency. For what I know
this comes from standard optical analysis tools. By the way, the compagny which
the the calculation is a strong supporter of the dark sky. It is a lifetime
member
of IDA and provided many support on the issue in Quebec. They are far from
your typical "Joe security lamp" provider. If we can settle this technical issue
with them, I think we are in trouble.
Yvan Dutil
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