Light Pollution: Chapter One
An article on Light Pollution
experiments in and around the St Austell area, by Tara Hill
The Spread of Light Pollution
Light pollution is all around us though not many people are aware of it's
existence. Britain is one of the worst culprits, it is ranked third in the light
pollution stakes after the USA and the Netherlands. Since the introduction of
street lighting over 100 years ago, light pollution has affected the
Identifying Different Types of Light Pollution
There are three types of light pollution.
- Light Trespass occurs when misdirected light shines onto a persons
property. The light can shine through a persons bedroom window causing sleepless
nights and general irritation. It can also disrupt a persons enjoyment of their
garden at night not just from an astronomer's point of view but also from a
person who enjoys studying nocturnal species.
- Glare often affects a person traveling in a vehicle, after driving
through an adequately lit area the driver approaches a security light which
shines directly into their eyes causing their dark adapted eyesight to be
blinded by misdirected light. The worst crime involving glare is security
lighting, it is so bright it actually camouflages anything going on behind the
light, therefore a criminal can go about his work.
- Skyglow is misdirected light, and this
is best described as the orange glow often seen creeping up into the night sky,
on a cloudy night it will even be apparent when looking directly above your
Skyglow is also an indicator of another type of pollution. Light likes to
travel in straight lines and if the source is directed straight up the light
will pass directly through the atmosphere without much resistance. However, most
light sources direct light down to the ground which is good, and out to the side
which is bad. The reason it's bad is because the atmosphere is thicker closer
to the ground where there is more water droplets to travel through and
scatter the light. Skyglow is apparent both close to home and further afield.
For example. Friends of mine live in a dark rural area on the coast near
St Austell. Although they are not astronomers, they enjoy looking at the night
sky and have fitted louvred luminaires in their garden, to reflect the light
downwards. Their main source of light pollution is the skyglow which is clearly
visible over Plymouth, over 20 miles from their home.
Other Factors Affecting Light Pollution
It is at this point air pollution also has to be considered. Power plants and
vehicles produce sulphate and carbon dioxide particles, the water droplets cling
onto and form around these particles. When the misdirected light hits the water
droplets, light is scattered, producing the skyglow. It is a sad fact that the
light fittings in general use today produce excessive light which is misdirected
making them inefficient.
Issues to Consider
The night sky is also an educational tool, astronomy is now a GCSE subject
opening up the subject to a lot more enthusiasts. It also provides important
information to scientists, helping us to understand how our planet formed and
what will become of it in the future. The night sky is full of secrets to be
discovered and therefore should be regarded as a Site of Special Scientific
There are several areas of light pollution that could be investigated but my
main objective will be to discover if and how much the night sky around the St
Austell area has been affected by street and industrial lighting. I have chosen
the night sky because as an amateur astronomer, the subject is close to heart
and the thought of losing the stars to light pollution would be unacceptable. St
Austell is set in a rural area, which should mean there are areas where the
stars are visible and where the sight in more populated areas are not. My
biggest concern is with the increasing population and the building of estates,
the areas where observing is possible will become less available as time goes
Therefore, the aims of the project are:
- Investigate the Light Pollution in the St Austell area
- Show with
photographs and diagrams, how light is scattered from various light fittings.
- Provide a source of information to educate people on the basics of light
pollution and it's effect of the Astronomer.
Light Fittings and their Effect on Light Pollution
Since the introduction of electrically powered street lighting at the end of
the 19th century, the night time environment has slowly but surely grown
brighter and brighter. This is due to increase in street lighting and the need
to light the way and provide a feeling of security. Over the last decade there
has also been an increase in other types of lighting, such as security and flood
Inside the home, people place light shades over their light bulbs, this
directs the light down onto the floor where it is needed and also reduces the
glare from the light bulb, making the home a warm, relaxing environment. This
activity is not always apparent when lights are designed for outside use.
Since the 2nd World War, the number of street lights have slowly increased
and in 2000 there were 6.2 million lighting columns in public ownership (www.ile.co.uk
22.02.02). Many of the older street lights contribute to the source of light
pollution known as skyglow, the orange tinge that lights up the sky over any
city, town and large village. Some cause light trespass, by shining light
through windows of houses. However, with public lighting this problem can
usually be rectified by contacting the owner of the light usually the local
council, who with reasonable cause will fit a more modern luminaire, which
should reduce the light trespass into a persons property (www.ile.co.uk
On average 30% of the light from street lights escapes above the horizontal,
from this figure the Campaign for Dark Skies estimates �53 million is wasted
lighting the sky ( Joy Griffiths 09.01.02). The reason for this waste is the
design of the older style street lighting.
These street lights are most commonly found on busy roads and areas of high
The smaller SCO. luminaires found in villages are serious light polluters as
can be seen in the photo they have been capped but the lamp is well below the
These post top luminaires, can be found on most estates, Aberdeen Close, St
Blazey is one example. They may appear to be sky friendly but a glow of orange
is noticeable around them on a misty night and photo one can show this. Bob
Mizon of The Campaign for Dark Skies, lived on an estate which recently had
these lights replaced with FCO. fittings, he has found the difference
incredible, proving that just replacing a few luminaires is worthwhile for the
immediate locality (Bob Mizon 2001). All the above light fittings are known as
Semi cut off luminaires. This means they have been capped but the light is not
totally shielded. Therefore if the lamp can be seen underneath the shield, in
the deep glass bowl, a certain amount of light can escape above the horizontal
(Joy Griffiths 09.01.02).
These older fittings are on the approved list of Cornwall County Council and
are used extensively. I have however noticed on my journeys around the St
Austell area that the FCO or Full cut off designs are being used where new
luminaires are installed for example on the A390 near St Mewan School and the
Carluddon roundabout. In St Austell itself, I have noticed on Trinity Street and
South Street, that the old luminaires have been replaced with the newer FCO
New FCO. Luminaires
(Pictures of all street lights provided by James Lantsbery, Cornwall County
The Full cut off design luminaires do not produce light pollution, they are
designed to place the light where it is needed the most. Reflectors and
refractors inside the shield will direct the light towards the ground, the light
is concentrated into one area. This is not only good for reducing light
pollution but also reduces the amount of electricity needed to power the lights.
The reason for this as light is concentrated into a specific area the full
resource of the light is used, a lower wattage bulb can be used, this reduces
electricity and the amount of fossil fuels used to power them.
Information Obtained from James Lantsbery, Cornwall County Council.
The lighting engineers of Cornwall County Council seem to be well aware of
light pollution and take the issue seriously, especially in rural areas. If they
receive complaints they will act on them and rectify the problem. Like any other
organisation the lighting department at CCC is ruled by a budget, money is
allocated to them at the beginning of the year for the maintenance and
replacement of street lights, however there is no fixed budget for replacing SCO
luminaires with FCO. The replacement of SCO luminaires will be a gradual process
taking place over a number of years. When the lights are replaced, whole streets
will be refitted at the same time using the original columns, the luminaires
will be constructed to provide the right light for the column spacing and
height. As already mentioned, the limiting factor is the amount of money
available to spend on new fittings, the older style SCO�s cost the council
�100, the newer FCO�s cost �150.
The conversation with James Lantsbery was very interesting as it showed that
large organisations such as Cornwall County Council are concerned about light
pollution. This could provide a role model for other institutions to follow
Domestic Security Lighting
Domestic security lights are becoming an increasing problem, the reason for
this is the design of the lights and the lack of instruction for fitting them.
Therefore, many people who are not aware of light pollution will fit the lamp to
the side of their building, with the fitting directing light out to the
horizontal, as no shielding is placed over the fitting, light will be scattered
in all directions. This not only causes skyglow, but light trespass and glare.
The average security light bought from the DIY stores is fitted with a 500
watt bulb, the Institution of Lighting Engineers state in their guidelines that
150 watts will do the same job quite adequately if installed correctly with the
beam lighting only the area required. To describe these lights as �security�
will only provide a �sense of security� to the householder, as the strong
light produces deep shadows, perfect cover for a person intent on causing
mischief. Again, as with the street lights using 150 watt instead of the 500
watt bulb will reduce energy costs and the production of CO2 and SO2 which
ultimately ends up polluting the atmosphere.
The light generated from these fittings will soon become the main source of
light pollution if nothing is done to improve their design. Although, there are
some good designs on the market fitted with motion sensors and shielding such as
the Astrica range, these tend to be more expensive than the polluting types.
Sports grounds such as the football club in St Blazey and industrial areas
such as Imerys, use flood lighting (see diagram 2a). The glow surrounding St
Blazey football club on a Wednesday evening is amazing, it lights up the streets
and the side of my house. Observing the night sky would be impossible when a
football match is on. A Friend who lives in St Merryn, has told me she can
see the lights from Newquay sports club from her house, a distance of 10 miles.
These lights are on every night of the week, even when the club is not in use.
The china clay industry also uses flood lighting extensively in the St
Austell area. I have driven past many china clay works at night and they all
seem to be lit up with floodlights. Obviously, safety has to be taken into
consideration for this type of lighting, and it would be wrong for me to suggest
they change their lighting system without proper consultation from a lighting
engineer. However, the use of flood lighting on the entrance to the Quarry Park
Tank Site, next to the Eden project in St Blazey could be improved. When I
visited the site at night, the flood light was on but the gate was closed
suggesting no activity, therefore the light could not be of any use to works
Globe lights can be found in various situations, they are used on pedestrian
crossings and can be quite often seen in car parks. The unshielded globe lights
contribute greatly to light pollution, they can also produce dark shadows due to
their design. The globe luminaire sits directly on top of the column, therefore
the column acts as a shield and produces a shadow around the base of the light.
The rest of the light is spread around in all directions. The Par Moor
Laboratories car park near St Austell has this type of lighting (see photo two
and diagram 2b), there is no shielding of any kind on these globe lights.
Although they look attractive, they do nothing for the appreciation of the night
Not all globe lights are bad however. For instance, the Asda car park
on the A390 near St Austell and Aylmer Square in St Austell has globe lights
installed (see photo three and diagram 2c). These lights have shields which
cover the top half of the globe and the bulb is placed up inside the shielding.
On closer inspection, reflectors were also noticed this would redirect the light
where it is most needed.
Other types of lights I have noticed in my survey area which are polluters
are the type that seem to be stuck to the side of a wall. For example porch
lights (see photo four), the owner of the property could fit shielding to the
porch light without too much trouble and direct more of the light where it is
needed. The light bulb could then be changed to a lower wattage, therefore
Other fittings of this type but larger have been seen on the side of Luxulyan
Village Hall and Par Health Centre (see diagram 2d). They give off a surprising
amount of light and I am sure contribute quite a lot to light pollution, as the
light is not shielded, there are several fitted to the buildings and are quite
large luminaires. In my opinion the lights at the Par Health Centre provide too
much light for their intended use as street lights are plentiful in this area.
Luxulyan Village Hall is probably more justified to have these lights as it is a
rural area with limited street lighting, although they could find a better
|A Post Top Luminaire with no shielding.
Produces all round light scatter as well as light tresspass on end of
||Unshielded Glode light in Par. Again all round
light scatter is evident.
|A well designed Globe light where the lamp is located within
the shielding. Light can only be directed downwards where it is needed.
||The results of an unshielded porch light.
Notice the light escaping above the horizontal and onto the side of the
|Old and New: The lamp on the left of the picture is the new
F.C.O Luminaire, while on the right is the older S.C.O design. Evidence
that there is a willingness to install the better F.C.O designs.
||Notice miss-directed light illuminating the tree. Skyglow is
very evident towards the horizontal, but with an increase in elevation,
more stars start to become visible.
|This photo shows both the older S.C.O and partially shielded
||A photo of the Aurora Borealis or Northern Lights.
If light pollution is allowed to continue unchecked, then this is a sight
that will become rarer. As an
amateur astronomer, I am obviously biased, but I am sure I am not the only
person who would rather look this than skyglow.
Forward to Chapter Two