LIGHT POLLUTION

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LIGHT POLLUTION LIGHT TRESSPASS 90 of the
Earths population cannot see the Milky Way.
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Merriam Webster's definition of light
pollution - Artificial skylight (as from city
lights) that interferes with astronomical
observation. Webster's definition is true, but
incomplete. Light pollution affects much more
than just astronomical observation bird
migration, nocturnal animals, marine life
migration, driver safety, public security, the
environment, economic savings, and city budget.

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• The Retina
• Forming an image on the back of the eye is
  not difficult,
• actually seeing the image is the hard part.
• The human eye has two sets of seeing systems
• the rod retina and the cone retina.

Diagram of eye above Diagram of retina (right)
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The rods are the more numerous of the
photoreceptors, some 120 million, and are the
more sensitive than the cones. However, they are
not sensitive to color. They are responsible for
our dark-adapted, or scotopic, vision. More than
one thousand times as sensitive as the cones,
they can reportedly be triggered by individual
photons under optimal conditions. The optimum
dark-adapted vision is obtained only after a
considerable period of darkness, say 30 minutes
or longer, because the rod adaptation process is
much slower than that of the cones. The rod
sensitivity is shifted toward shorter wavelengths
compared to daylight vision, accounting for the
growing apparent brightness of green leaves in
twilight. While the visual acuity or visual
resolution is much better with the cones, the
rods are better motion sensors.
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The cones provide the eye's color sensitivity.
The green and red cones are concentrated in the
fovea centralis. The "blue" cones have the
highest sensitivity and are mostly found outside
the fovea. The cones are less sensitive to light
than the rods, as shown a typical day-night
comparison. The daylight vision (cone vision)
adapts much more rapidly to changing light
levels, adjusting to a change like coming indoors
out of sunlight in a few seconds. Like all
neurons, the cones fire to produce an electrical
impulse on the nerve fiber and then must reset to
fire again. The light adaptation is thought to
occur by adjusting this reset time. The cones
are responsible for all high resolution vision.
The eye moves continually to keep the light from
the object of interest falling on the fovea
centralis where the bulk of the cones reside.

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Measuring light pollution Since 1998 unsaturated
data become available, allowing quantitative
measurements of the upward light flux emitted by
sources. However satellite data dont give any
direct information on the effects of this light
flux on the night sky due to light pollution
propagation.   The satellite measures the upward
light flux of sources on the Earth surface based
on DMSP satellite data and then compute the
effects on the night sky modeling the light
propagation in the atmosphere. 
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• Light Pollution occurs in three forms
• Sky Glow
• Light Trespass
• Glare

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Skyglow 1. It causes an atmospheric phenomenon
known as skyglow.   Have you ever noticed the
clouds overhead glowing an eerie pink, white, or
orange color before?   This wasted light is known
as skyglow.   It happens because of poorly
designed and improperly aimed light fixtures
called luminaires.   Luminaires that do not offer
adequate shielding usually spill wasted light
into the sky and across property lines where it
does not benefit anyone.   When light spills into
the sky, it reflects off of tiny airborne dust
and moisture particles.   This happens even on
very clear evenings, too.   The skyglow
phenomenon directly affects the scientific
research of amateur and professional astronomers.
  It also affects everyone else who simply enjoys
a dark night sky abundant with stars overhead.  
Skyglow is a curable condition, and we can still
have adequate and safe illumination in the
outdoor environment.
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Light Trespass 2. Another form of Light
Pollution is when illumination crosses property
lines.   This is called Light Trespass.   Most
people today have experienced light trespass to
some degree.   When someone else's illumination
shines through your windows at night it is light
trespassing onto your property.   This is not
only a nuisance, it can also affect your safety.
  Light trespass can prevent you from using your
property outdoors at night when wishing to gaze
at the stars while lying on a blanket or viewing
through a telescope or binoculars.
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Glare 3. Light pollution also occurs when too
much illumination is applied to an area and a
condition called glare results.   Glare is
defined as a visible source of illumination that
causes a reduction in visual performance or an
irritation.
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Light Pollution Awareness Groups and Associations
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International Dark-Sky Association IDA's goals
are to be effective in stopping the adverse
environmental impact on dark skies by building
awareness of the problem of light pollution and
of the solutions, and to educate everyone about
the value and effectiveness of quality nighttime
lighting.
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The New England Light Pollution Advisory
Group The New England Light Pollution Advisory
Group (NELPAG) is a volunteer group founded
during the autumn of 1993 for the purpose of
educating the public on the virtues of efficient,
glare-free outdoor night lighting -- and the
tremendous benefits of low-lumen
(low-light-output) lighting for many (if not
most) outdoor applications.
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Examples of Poorly designed fixtures, wasting
light, and energy.
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POLLUTING FIXTURES
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NON POLLUTING FIXTURES
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LIGHT POLLUTION. Spotlight lighting. THE USE OF
ASYMMETRIC SPOTLIGHT WHEN IT IS POSSIBLE, MEANS
IN GENERAL AN INCREASE OF 25 OF ILUMINATION
LEVELS AND UNIFORMITY WITH RESPECT TO SYMMETRIC
ONES, BECAUSE THE ASYMMETRIC EMIT ALL THEIR LIGHT
DOWNWARDS.
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LIGHT POLLUTION. Light bulbs. THE LESS HARMFUL
BULBS ARE LOW PRESSURE SODIUM LAMPS, THEY EMIT IN
A NARROW BAND OF THE VISIBLE SPECTRUM LEAVING THE
REST CLEAN. THESE TYPES OF BULBS CONSUME 5 TIMES
LESS THAN INCANDESCENT BULBS, 2,2 TIMES LESS THAN
MERCURY BULBS AND 1,5 TIMES LESS THAN HIGH
PRESSURE SODIUM AND FLOURESCENT BULBS.
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THE LIGHT POLLUTION. Adaptation.
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PHOTOGRAPHY of ADAPTATION AFTER 2400h
                                                  
                                                  
                                                  
    TOTAL UPWARD FLUX REDUCTION (LIGHT
POLLUTION) 85
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• Light that trespasses onto neighboring property
  is annoying, wastes energy and obscures the night
  sky.
• You can reduce lighting trespass by
• Aiming lights down
• Choosing fixtures with hoods or visors that
  control light
• Installing motion sensors to turn lights off
  automatically when they are not needed
• Using the correct wattage fixture. If 70 watts
  will do, why use 400? Lighting should not be
  overly bright in relation to the surrounding
  area.

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• LIGHT POLLUTION. Advantages and benefits.
• REDUCE ENERGY CONSUMPTION AND INDIRECTLY THE USE
  OF FUEL, CO2, NO4, SO2 EMISSION AND OTHER
  PARTICLES.
• PROTECT THE NOCTURNAL ENVIRONMENT, REDUCING THE
  DISTURBANCE OF NATURAL HABITATS (ANIMALS, PLANTS
  AND ECOLOGICAL PROCESSES). PROTECTION OF
  NOCTURNAL BIRDS.
• AVOID GLARE FOR AIRCRAFT AND SHIPS.
• AVOID DISTURBING NEIGHBOURS.
• FACILITE ASTRONOMY FOR BOTH PROFESSIONALS AND
  AMATEURS.
• PRESERVE A DARK SKY IN HARMONY WITH THE UNESCO
  UNIVERSAL DECLARATION OF FUTURE GENERATION
  RIGHTS
• " Future generations have the right to an
  undamaged and unpolluted Earth, including the
  right to a clean sky."

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