NELPAG Circular No. 15 1997 April 14
New England Light Pollution Advisory Group (NELPAG)
Editor: Daniel W. E. Green [Smithsonian Astrophysical Observatory;
60 Garden Street; Cambridge, MA 02138] (telephone 617-495-7440)
e-mail: green@cfa.harvard.edu
Secretary: Eric Johansson (telephone 508-667-0137)
email: esj@harvee.billerica.ma.us
"Subscription" to this irregular news/information Circular is available by
sending self-addressed, stamped (32 cents in the U.S.A.) regular-sized
(9.5x4-inch) envelopes (SASE) to Dan Green at his postal address, or by
sending your e-mail address to NELPAG-REQUEST@HARVEE.BILLERICA.MA.US (Internet).
Contributed information for this Circular concerning outdoor lighting problems
in New England (or pertinent info from outside New England) are always welcome.
Please circulate this newsletter to all interested parties. Look at our
World Wide Web site at URL http://www.cfa.harvard.edu/nelpag/nelpag.html
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NEWS ON THE MASSACHUSETTS STATE FRONT
Dr. Robert Stefanik (Harvard-Smithsonian Center for Astrophysics) and I
were present on Tuesday, April 8, for a public hearing before the Energy
Committee on energy-related bills at the Massachusetts State House in Boston.
We presented our case for 10-15 minutes to a very receptive group of State
Senators and Representatives, who also asked good questions. This new bill
is House Bill H.3418 in 1997, but is worded essentially the same as in 1996.
The main sponsor of the bill, Rep. Jim Marzilli of Arlington, is indicating
interest in stepping up the intensity in getting this bill moving out of
committee, and we're already lining up media interviews on the bill with
radio and newspapers in the Boston area. This spring, we will take up Kelly
Beatty on his offer to donate a copy of mailing labels for all Massachusetts
subscribers to Sky and Telescope, which we will use to mail a one-page flyer
to these subscribers giving the text of the proposed bill, along with a plea
to write three letters (to their State Senators and Represenatives, asking
them to be co-sponsors of this bill, and to the Governor). Hopefully we'll
be able to raise enough additional co-sponsors and enough media attention to
do something with this important legislation. One question was raised in which
the pending bill may have a slight problem: "How does this bill lead to
energy conservation and therefore savings in spending?" For those unfamiliar
with the Mass. bill, it simply states that any state-funded new or replacement
outdoor lighting must be full-cutoff luminaires (with the usual exceptions
regarding emergency lighting, etc.). So I explained to the Committee that, in
the case of replacement lighting (in which an existing "broken" dropdish
luminaire is to be replaced with a new cutoff fixture), where there is a cost
to go from a dropdish head to a cutoff head, the wattage would need to be dropped
on the lamp to get the savings in dollars; but the wattages on most new
metal-halide and sodium lamps are way too high anyway (as I've noted in these
pages), so this simply means a return more toward the earlier mercury-vapor
lighting levels.
The April 14th edition of the Boston Globe brings a very welcome article
on this subject (p. C2) entitled "Prospects brighten for bill to control
'light pollution'", by Globe reporter Peter J. Howe. Our bill, he writes,
"appears to have a good chance at coming before the full Legislature for
action within the next month." This is largely because there was a turnover
in leadership of the Energy Committee, through which the bill has been filed
and through which acceptance must be gained to pass to the House for a vote
by the Legislature. We ask our readers to write to the co-chairmen (Sen.
Robert Bernstein of Worcester and Rep. Dennis Murphy of Springfield), and
especially to Rep. Jim Marzilli of Arlington, to thank them for their support
of this bill. Now is the time to call your Mass. state Representative and
Senator to ask them to support this bill, as "Murphy and Bernstein said they
hope to have a committee executive session within three weeks at which the
lighting bill --- probably in an amended version --- could be sent to the full
House for a vote." The amendment discussion apparently has to do with the
lighting historical edifices (of which there are many in Massachusetts). I
have asked Rep. Marzilli via e-mail to try to see if historical edifices
that require new lighting be lit from above, not from below. I will pass
along more details as I learn of them. --- D.W.E.G.
MORE ON LEXINGTON, MASSACHUSETTS
Following a request by a newspaper writer in Lexington (who writes for
the local Lexington newspaper, as well as for papers in the general Boston
area), my son and I drove around the town of Lexington at night and compiled
a list of "The Good, the Bad, and the Ugly" in outdoor lighting. The list
was provided to the newspaper writer and has been made available on the
NELPAG World Wide Web homepage at URL
http://www.cfa.harvard.edu/cfa/ps/nelpag/lex.html. I would like to hear of
similar list compilations elsewhere, and will post such lists on the NELPAG
Web site (ask in advance for format). I will inform readers of these NELPAG
Circulars of responses that occur as a result of the Lexington compilation.
I plan to provide a more complete update on the happenings in Lexington
in the next NELPAG Circular. -- D. W. E. Green
NEWS FROM PLYMOUTH, MASSACHUSETTS
The Boston-area newspapers have made much of reporting the news from
Plymouth concerning an outdoor night-lighting bill put forward by attorney
William Abbott (who was aided by information from NELPAG Circular 10c,
particularly the Tucson ordinance). This amendment to the zoning bylaw
passed the Plymouth Planning Board on Feb. 18, and this week the bylaw will
be voted on by the Town Meeting. Word from the Boston Globe (which ran a
story on this last week) is that there is virtually no opposition to the
3-page bylaw. The text of the bylaw will be given in the next NELPAG
Circular, but the chief points are (1) that light fixtures with incandescent
bulbs more than 150 watts must be fully shielded (full-cutoff fixtures); (2)
that all metal-halide lamps must be full-cutoff; (3) searchlights for
advertising purposes are prohibited; (4) "the use of laser source light or
any similar high intensity light for outdoor advertising or entertainment,
when projected above the horizontal, is prohibited"; (5) "outdoor light
fixtures used to illuminate an outdoor advertising sign shall be mounted
on the top of the sign structure"; and (6) recreational-facility outdoor lighting
shall be turned off as close to 10:30 or 11:00 p.m. as possible.
I am amazed at how rapidly lighting issues are progressing right now
in Massachusetts, and hope that this means that such city/town bylaws and
ordinances can be introduced routinely in New England and passed rapidly into
law in the next couple of years. The public is rapidly awakening to the ills
of bad nighttime lighting, and none too soon! --- D.W.E.G.
SOME THOUGHTS ON LIGHT POLLUTION FROM NEW MEXICO
[Editor's note: this was distributed over the NELPAG e-mail exploder
by Warren Offutt, an amateur astronomer (and retired engineer) residing in
southern New Mexico. It is worthy of repeating here. It was addressed to
David Smith in Texas regarding requests for help in presenting the outdoor
night-lighting bill that is pending in the state legislature there.]
I've been working on light pollution issues in Otero County, NM, for
several years. Although I don't have the time to work up a detailed
statement for you, the following comments might be helpful.
First, the usual definition of "full cut off luminaire" is one that
specifies shielding to keep light below a horizontal plane drawn through
fixture itself. Unless the Highway Department is trying to illuminate the
sides of mountains that are at higher elevation than the luminaires themselves,
full-cutoff fixtures have no deleterious effect on how far the "throw" extends
between fixtures. Indeed, full-cutoff fixtures aid, not hinder, the light
levels at a distance because the light that formerly was wasted in an upward
direction is directed down into the effective area.
Second, knowledgeable lighting engineers today take the position that
horizontal plane cutoff is inadequate and best results are obtained with a
cutoff of illumination above an angle which is variously 15 to 20 degrees below
the horizontal. The reason is that elementary calculation of illumination level
fall off with distance from the fixture shows that broad-distributing "area"
illuminating fixtures (i.e., not spotlights) can not render effective
illumination at horizontal distances farther than about three times the height
of the fixture. Illumination, even if it were isotropic from the luminaire,
falls off as the square of the distance from the fixture, and practical
fixtures are not isotropic anyway, further exacerbating the light intensity
fall off with distance. At distances farther than about three times the height
of the fixture, the illumination level over the working area becomes so uneven
and contrasty that illumination farther out is ineffective, regardless of
absolute intensities.
(There is a practical limit to the differences of illumination level that
the human eye can accommodate within a working field. The three-times
rule-of-thumb figure above, for practical luminaires, corresponds to about a
10-to-1 range in the illumination levels seen by the eye. Making the light
brighter does not help, because the eye's iris closes down according to the
brightest parts of the scene, causing the dimmer parts of the scene to
appear dark. It is elimination of excessive differences of illumination in a
scene and the absence of direct glare that make for good seeing.)
A distance of three times the fixture height corresponds to a cutoff angle
of about 19 to 20 degrees below horizontal. When a series of poles is used,
spaced at intervals along a roadway, in the far-out extreme of a pole's
effective area, there is a contribution to illumination from the next pole, so
a slight relaxation of the 19 degree angle is permissible. As mentioned above,
15 degrees is a good working figure.
The use of luminaires designed to these modern standards actually increases
(not decreases) the illumination level in the fringes of the working area,
because light that was formerly wasted upward is now directed into those areas.
I don't have the increase figures for roadway luminaires, but tests on the
standard NEMA head fixtures show an increase of illumination levels to about
195% of the former illumination level with installation of products like the
commercial "Sky Cap", or equivalent. Thus, for the same illumination level in
the working area, half the wattage will provide the same illumination. Half
the wattage, of course, means halving the electric power consumption, all other
things being the same. For roadway luminaires, I estimate an illumination
increase with proper shielding to perhaps 115% of the unshielded level.
An often overlooked fact is that the actual illumination level is only
part, and not the most important part, of the matter. The presence or absence
of direct glare is more important than the actual illumination level. Witness
the difficulty of seeing when driving into a sunset --- the illumination
intensity is very high, but seeing ability is poor because of the direct glare
from the sun. The same principle applies to night roadway lighting. Glare
from distant fixtures is far more harmful to visibility than marginal
illumination level. Again, a luminaire which cuts off at about 15 degrees below
the horizontal not only concentrates the light within its area of effectivity,
but also (more important to good visibility) eliminates glare in the eyes of
motorists and pedestrians beyond its area of effectivity. They will be able to
see hazards within the effective area much more clearly from much greater
distances with the elimination of the direct glare.
Everyone benefits from properly shielded luminaires, but special benefit
accrues to senior citizens and persons with slight sight impairment. Seniors,
in particular, experience eyesight deterioration which makes glare difficult to
accommodate. Glare impairs their seeing ability much more than an absolute
level of illumination.
Even though an area lighting fixture can provide effective illumination
no further than about three times the pole height, it can cause harmful glare to
a very much greater distance because the glare is a direct ray rather than being
reflected off intervening objects such as the roadway, pedestrians, animals,
vehicles or hazards on the road.
The best source of comprehensive standards dealing with actual light levels
is the IESNA -- The Illuminating Engineering Society of North America. Their
standards cover virtually every situation for which lighting is needed. However,
even their standards are just beginning to recognize the importance of glare
elimination and some of their older releases have not yet been brought up to
date in addressing this matter.
There was a Federal highway lighting standard published by the GPO about
25 years ago, which is now out of print and considered obsolete. I'm not
saying there is no current Federal highway lighting standard, but if there
is, I have not been able to find one. (If you find one, I'd be grateful for
information about it.) An assertion that Federal highway standards dictate
something that determines pole spacing might not be supportable and should be
verified. -- Warren Offutt
SUBDIVISION PROPOSAL FOR OUTDOOR LIGHTING
The subdivision covenant restriction I wrote for the local Planning
and Zoning commission is below. The notes at the bottom are my notes and
are not distributed to developers unless they ask for the basis of the numbers.
--- Warren Offutt
*Lighting Guidelines and Restrictions*
The purposes of these Guidelines and Restrictions are to provide
residential outdoor lighting levels meeting ANSI-recommended safety/security
levels of 1 to 5 Lux in typical residential applications while preserving the
natural night-time appearance and beauty of the area and preserving the
enjoyment of the unspoiled natural character of the area; preventing light
trespass and glare intrusion onto neighboring property, parks or roads; enhancing
property values; conforming with the New Mexico State Legislature's resolution
declaring New Mexico a "dark sky state"; preserving the value of the dark night
sky for astronomical research, education and recreation; and avoiding toxic
mercury exposure which might arise from accidental breakage or improper disposal
of prohibited lamp types.
Lighting fixtures, appliances or devices which provide out-of-doors
illumination, whether intended or incidental, shall conform to the following:
1. Such fixtures, appliances or devices shall be equipped with shields
or hoods to confine illumination to within the property owner's
boundaries. No light from any such fixture, appliance or device shall
be permitted to trespass on to neighboring private or public property,
nor shall any direct rays be permitted above an angle of 15 degrees
below horizontal.
2. Continuously on "dusk-to-dawn" lighting controlled by any automatic,
non-manual means is prohibited.
3. Mercury-vapor lamps, search-lights, decorative lasers and continuously
flashing lights are expressly prohibited. Full-cutoff-style luminaires
are recommended for area lighting; however, all area lighting, regardless
of type, shall be in strict compliance with these Lighting Restrictions.
4. Outdoor lighting fixtures shall not exceed the following wattages:
75 watts for ordinary, screw-in incandescent lamps
50 watts for quartz, halogen, HID or similar lamps
35 watts for High Pressure Sodium or fluorescent lamps
25 watts for Low Pressure Sodium lamps
5. Where security lighting is needed, the use of motion-detector controls,
which activate the light for periods of less than 5 minutes when motion
is detected, is encouraged. Such fixtures are exempt from the
requirements of paragraph 4., but are not exempt from the requirements
of paragraph 1.
6. Decorative holiday lighting using lamps of less than 10 watts, which
are in place for holiday seasons not exceeding 3 weeks each year, is
exempt from the requirements of these Lighting Restrictions.
Notes:
Assuming the typical residential fixture is mounted at a height of 20 feet on
one side of a house, the practical coverage area is semicircular with radius
of approximately 60 feet, for an area of 5600 square feet. The lumen output
for the following lamps should yield the nominal Lux levels shown, when the
lamp is installed in a fixture shielded to direct the light to the illuminated
area. Note that these levels are not intended to be bright "anti-intrusion
security" levels, because that function is to be provided by motion-detector
lamps.
LAMP TYPE BULB "SIZE" LIGHT OUTPUT
Incandescent 75 watts 2.2 Lux
Quartz Halogen, etc. 50 watts 1.8 Lux to 5 Lux
HPS 35 watts 7.8 Lux
LPS 25 watts 8.9 Lux
DRAFT OF A PROPOSAL FOR A MEETING ON LIGHT POLLUTION
This is a proposal that might be suitable to submit to environmental grant
making foundations in the private sector. About 100 of the 600 sources listed
in a catalogue with this name might possibly be interested in light pollution
as an environmental problem.
This draft describes a meeting that I propose for your consideration,
remarks and comments, and your information in general. If you know others who
might be interested, I would be glad to know of them.
Outdoor lighting and its impact on night sky brightness, is of concern to
people working in a number of fields. Among these are the study of stars,
migratory birds, sea turtles, and energy conservation. Yet this remains a
field quite without paradigm, due in part to a lack of contact between
scholars working in these disciplines.
In the last few years, public interest in, and concern about light
pollution has risen markedly. The application of the simplistic
"more-is-always-better" perception to street lighting is giving way to a more
realistic and balanced viewpoint. Furthermore, manufacturers now offer a
variety of outdoor lighting fixtures with a wide range of impact on the
environment. For example, shielding (constraining light to shine only below
the horizontal plane) is one of several factors in available luminaires that
reduce direct glare and energy waste without compromising personal and traffic
safety.
I propose a conference aimed at cross-fertilization, at bringing scholars
in the fields affected by outdoor lighting together, in order to work in
concert toward a common goal; the reduction of night sky brightness, partly
through a reduction of energy waste. At all levels of organization and
participation, a breadth of viewpoints and interests would be represented, in
order to examine light pollution from many different perspectives.
I visualize a meeting of invited and contributed papers of course, but
also of panels or workshops, aimed at integrating these perspectives into a
workable and realistic approach to the problems produced by an artificially
brightened sky. The conference would likely extend over several days, and
could be held in Middletown or New Haven (with its better facilities for such
meetings) or Florida.
-- Arthur Upgren (June 6, 1996) [e-mail aupgren@wesleyan.edu]
[During the fall semester of 1996, Prof. Upgren taught a course on
light pollution at the Center of Humanities, Wesleyan University. It
was the first on this subject for college credit, to the best of his knowledge.
We'll provide an update on this and other recent Connecticut developments,
including their state legislation on outdoor night lighting, in the next
NELPAG Circular. Upgren notes that a "small bill got passed" by the
Connecticut state legislature last year "with a requirement to limit new
lights supported by state funds". -- Ed.]
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The NELPAG supports the International Dark-Sky Association and recommends
that all individuals/groups who are interested in the problems of light
pollution and obtrusive lighting should subscribe to the IDA Newsletter
(IDA membership costs $20.00 per year; send check to
International Dark-Sky Association, 3545 N. Stewart, Tucson, AZ 85716).