Filters and Light Pollution
July 15th 2011 10:00
Category: Astronomy
Light pollution is an ongoing problem not only locally but also globally.
Many amateur astronomers have to dodge the light as it were seems
ironic we need light to see celestial objects.As more people live in cities
or densely populated areas the light pollution continues to spread.
The artificial light spreads beyond the cities and large towns causing
sky glow, sky glow is the brightening of the night sky by unnecessary light.
When street lighting is used wisely it can be beneficial to all concerned.
Some municipal government agencies have the idea that more
light always results in better safety and security this is a misconception.
Town planers need to design the lighting to suite the specific area and
only install lights where there needed and not place street lights indiscriminately because it is deemed
as security issue.
Light overkill results in wasted energy and money and does not
necessarily offer better security.
There many things we can do to minimise light pollution that is turn
off any unnecessary lights.
Do filters help in reducing the affects of light pollution ?.
The answer to this question is mixed. While some filters can help in reducing light pollution when used in astronomy.
by the same token
they can cause the celestial object to become dimmer thus cancelling
out any small benefit.
Light-pollution reduction filters ( LPRFs) Filters work by rejecting
light that is emitted at certain frequency.
The problem associated with using filters is that you want the filter to reject the unwanted portion of the light spectrum while letting in the desired parts, no pollution filter I know of will meet this criteria no matter how good they claim it to be.
In astronomy we use two types of filters one type is called a broadband and the other are referred to as narrowband. There are other filter subsets for example Oxygen III (O-III) H-beta and Ultrablock or UHC filters.
The O-III does a does a job enhancing planetary nebula and some emission nebulas .
Video by dakotalapse
The broadband (or sometimes called wideband) filter blocks the
least amount of light and can enhance some nebulas especially
when used in astrophotography applications these filters will not
reduce light pollution.
design your own lighting new site Use this Link Opens New Window Link
Click Here to Open New window Design your Lighting See how a few lights affects the night sky
Narrowband filters, are sometimes called "line" filters, since they only
admit one or two emission lines and reject just about everything else.
These filters are generally used for enhancing dim objects, but there is a catch.
Narrowband filters work well is when the celestial objects emits enough of the desired light frequency.
When dealing with filters it can be a bit of a mine field. I suggest if your looking to use a particular type of filter is to do research first.
Acknowledgements
Lighting simulation courtesy of Need-Less.org.uk
Daniel Nixon,CmooreStars, moeris00
International Dark-Sky Association(IDA)
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