Let there be dark (Part 2 of 3)

5 08 2010

Continuation from Part 1

Neither is light pollution confined to cities. Even tens of kilometres away from the hustle and bustle we can see its effects. A new generation of 500W security floodlights, commonly available in hardware stores, shed a glare that can be seen from miles away. Put a dozen of these together and even a secluded hamlet can look like the Las Vegas strip. Perhaps the most problematic aspect of this kind of light pollution is “light trespass”, when unwanted light from a neighbour’s fixture enters your property. Light trespass can be especially annoying when you’re sitting on your deck and you have to shield your eyes from a neighbour’s floodlight.

Concerns about light pollution have been with us for at least 30 years, and it’s a global problem as well. Look at any picture of the night-time Earth from space and you will see cities across the globe lit up like Christmas trees. The responsible lighting guidelines that have resulted from the awareness campaigns are really what I would call “sensible lighting” guidelines. Not only do they lead to better lighting, they also use less lighting, saving you money. The ideas can even be encapsulated in three simple words shade, switch, sufficient.

Fully shaded fixtures, or those that aim light downward are the most efficient way to light a given area. In an uncapped or undirected fixture, the light directed upwards is simply wasted light. Adding a reflector to direct the light down, or using a bulb that’s half-mirrored, ensures that the light is directed where you need it. Because you’re not wasting the upward bound light, you can now use a lower wattage and less energy even though you’re lighting the same area. That’s good for your pocket book and good for the sky.

Switching off lights when you don’t need them is something everyone was taught by Mom and Dad, yet we can all be just that bit lazy about doing it. While the biggest offenders in this category are usually businesses with big signs, there is still room for improvement on the residential side. For many of us, leaving a light on is a step we take to feel more secure. But most thieves say signs of occupancy are the key deterrent, and lights are only one part of that. So if your car is home and you’re tucked up in bed there’s really no need for that porch light to still be on. There are also technologies that can help. Floodlights controlled by motion sensors are a great help in reducing light pollution. In rural environments the sensors can be slightly annoying because animal guests can set them off, but many new detectors allow you to adjust their sensitivity. Adding a shade and making sure that the light points down at 45 degrees towards the ground also prevents glare.

With these improvements in place it becomes possible to use a lower wattage light as well, and that brings us to the final aspect of responsible lighting, namely using a sufficient amount light. It’s a bit of a Goldilocks problem, too little light and you can’t see, too much light and you’ll be dazzled by glare, and that can even be dangerous. Once your eyes adjust to very bright light, any neighbouring unlit areas will appear much darker and you can easily find yourself stumbling around. The best lighting is uniform and low-intensity. If you’re not sure about what’s acceptable you can always try experimenting with different wattages and see what the minimum is. If getting wiring to the right place is an issue you can even consider solar powered floodlights, and the 15W LEDs can be surprisingly bright.

Tomorrow: Part 3, the impact on the environment and Kejimkujik National Park, our newest Dark Sky Preserve.

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2 responses

5 08 2010
Let there be dark (Part 1 of 3) « Ecogirl & Cosmoboy's Blog

[…] Part 2, What can we do about light […]

6 08 2010
Let there be dark (Part 3 of 3) « Ecogirl & Cosmoboy's Blog

[…] Let there be dark (Part 3 of 3) 6 08 2010 –Continuation from Part 2– […]

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