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Events & Lecture Programme
In the Media
The Dick Chambers Sutton-at-Hone Observatory
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campaign for dark skies
Table of Contents
Light Pollution Filters
CfDS - Campaign for Dark Skies
Sign the UK Government
to improve street lighting.
Bexley council have a very poor track record at delivering lighting that doesn’t pollute the skies. If you are concerned about light pollution you can contact Bexley council on
Help measure the light pollution in your area see
Light pollution in Bexley is one of the worst in the country. Simon Dawes took these photos with an old compact digital camera, using exactly the same settings for both images. This is such a waste of energy, the light should be on the ground not lighting the sky!
Image from Bexleyheath
Same settings from Norfolk
Bexley council plan to install brighter street lights
Too busy to write an email but still concerned?
Let Simon Dawes write an email for you. Simon will be happy to craft the email so that all you have to do is send it. Speak to Simon during class tea breaks.
Helpful advice is available on the
The following are some arguments you might consider using when contacting the council…
£1 Billion is wasted every year by light produced that shines upwards.
Money wasted by inefficient UK street lights sending light into the sky cost £120M in the last 12 months
From 2002-2005, the City of Calgary (Canada)
replaced all their street lighting
with efficient lights - saving the city at least $2 million a year (2005 prices)
570,000 Tonnes of additional CO2 is pumped into the atmosphere due to inefficient UK street lights lighting the sky rather than the area that needs lighting.
A 500W security light on all night uses 2 tonnes of CO2 per year
A new diesel car would produce the same amount of pollution as a typical single 500W floodlight per year
Lighting does not reduce or increase crime.
Essex police state '
A year on year comparison for April 2006 to May 2007 [when street-lights were left on all night] and April 2007 to May 2008 [when street-lights were turned off at midnight] has shown that night-time crime has almost halved in Saffron Walden and reduced by over a third in Dunmow.'
The Influence of Street lighting on crime a fear of crime states
The principal conclusion is that no evidence could be found to support the hypothesis that improved street lighting reduces reported crime
The UK Governments Home Security & Crime reduction web site
states Harsh, glaring floodlights are not a deterrent to criminals
There is now significant evidence showing that exposure to light at night can disrupt the body's production of melatonin, a brain hormone best known for its daily role in resetting the body's biological clock. Secreted primarily in the brain, and at night, melatonin triggers a host of biochemical activities, including a nocturnal reduction in the body's production of oestrogen. Research has shown that decreasing nocturnal melatonin production increases an individual's risk of developing oestrogen-related malignancies, such as breast cancer.
When writing an email to the council it can also be useful to include links to organisations that support your point, Simon has listed some below…
The Campaign to Protect Rural England
The Government's Home Security & Crime Reduction website
Research by the UK Home Office** supports observation that excessive lighting **does not reduce crime** e.g. research papers
The Institution of Lighting Engineers guidelines
Clean Neighbourhoods and Environment Act 2005
Light Pollution Filters
Light pollution filters work by filtering out the light at the frequencies you are not interested in. they come in two forms...
Narrow band filters
These stop all light except the frequency you are observing in, these are great for nebulae, but do not work for stars or galaxies.
These try to block the common frequencies used by street lights (these do not work for 'white' light or LED street lights).
Light pollution filters may help but do not substitute for dark skies, here are a couple of examples of images take from light polluted Gravesend with and without a light pollution filter by member Brian Thompson, for more information download the presentation given to the class during a
Click on image for full resolution
- note images are not processed and are a single frame.
160s with LPF
30s without LPF
NOTE: Light pollution filters will
filter the new white light street lights as these emit light across the full spectrum, including OII and Ha.
To give an idea of how light pollution filters might help these images were taken on a
by Simon Dawes.
shows the reflection of lights from the underside of clouds, so gives a good view to the amount of light going up
Neodymium is a
light pollution filter, very cheap but not that effective, best in areas that still use low pressure sodium lights.
Unbranded UHC, does a good job of blocking out the street lights but I have found that bright stars ghost, and has a sligt green cast.
Orion UltraBlock, this is a narrowband filter, it blocks all but Ha and OII light emitted by nebulae, works very well.
Comparison with and without filters
Light narrow band light pollution filters do not work well on stars, globular clusters or galaxies indeed you may be better without a light pollution filter on these subjects, below are two images of the same sky taken on a Canon EOS 400D ISO 800, 30s exposure, untracked, 18mm focal length @ F5.6 one with no filter and one with the Orion Ultrablock. Note how more stars are visible without the filter but also how well the ultra block blocks that horrible red sky.
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