Simcoe Skies Astronomy

Guide to Friendly Nighttime Lighting

  Think back to when you were a kid. Maybe you were at home, or visiting someone in a rural location, or on a camping trip, and you looked up at night... and were overwhelmed by the number of stars in the sky. Tonight when you look up, do you see as many stars, or do you see them dwindling as the years pass? No, it's not your failing eyesight. Yes, the stars are still there, you just can't see them. Why? Because light pollution is taking its toll on this amazing natural wonder that we should be fighting to preserve for our children and grandchildren.

What can you do to help preserve the night sky?

Lighting is one of mankind's best friends. We can read by it, do work or leisure activities by it, and it literally brightens our lives. Lighting can be used for mood, for emphasis, or for practical application. The key to "friendly" nighttime lighting is keeping it private. You wouldn't blast your favourite Billy Joel album at full volume with the windows wide open after 10pm, inflicting it upon your neighbours. But have you stopped to think about the visual impact that your nighttime lighting has on those who live around you? Or have you thought about what it's doing to the sky?

Ponder this question: When you turn on the light in your home at night, do you do it to help you see, or so others can see into your home and to light the outdoors? If you chose the first answer, are you getting the most out of your lighting, or are you wasting some of your light and your money by letting it escape through your windows into the night, eroding away the darkness?

It's a well known fact that by closing blinds or drapes at night, it helps to brighten your home. This is because the blinds or drapes generally reflect the light back, instead of allowing it to pass through the windows to the outdoors. This has a number of benefits, ranging from security (people can't see in) to being able to use lower wattage of lights or fewer lights to attain the same lighting level. This not only saves energy, but it saves you money. The other benefit to closing blinds or curtains while your lights are on, is that it helps to prevent light pollution, keeping your light on your property, and keeping it from having an adverse effect on the starry sky.

Outdoor lighting is another issue that we all need to think about. It's far too easy to leave an outdoor light on and walk inside, forgetting the impact that it has beyond our own property. Outdoor lighting is the primary culprit for causing the extinction of our starry night sky. "Friendly" outdoor lights don't waste light by shining it horizontally or upwards vertically. How much are you paying to illuminate the clouds? Does your outdoor lighting shine off your property, or is it hooded such that it efficiently puts the light only where you need it? If you use it for security, do you have it on a motion sensor? Is it positioned so the light shines on the ground, or is it set to glare in a potential witness's eyes when it comes on? Outdoor lighting should be set to shine 10 degrees UNDER horizontal, to contain the light and avoid waste. If it's shining out and up, you're wasting 50% of the energy, and 50% of the money you're paying for it. Downward-facing lighting is twice as efficient, and can save your money and our night sky.

Tonight after dark, take an inventory of your lighting. How much are you throwing away into the night? Does the illumination from your lighting stay on your property, or does it light up the neighbours' outside walls and shine in their windows? Again, think back to that starry sky of your childhood... and let's all work together to bring it back.

Amateur astronomers are impacted even more by wasteful lighting than the average public, since it severely limits our hobby. We need our "night vision" in order to find our way around the sky and find those faint, far-away objects that we're looking for. One of the wonders of the human eye is its ability to operate over a very broad range of light levels. The eye can function rather effectively to changes in brightness of as much as 1,000,000,000 times (yes, that's one billion times). In low light conditions, the eye will "dark adapt". An extreme example is when you walk indoors on a bright, sunny day. A few moments later, your eyes adapt and the lighting level seems normal. This happens at night as well, but NOT where the glare of lights keeps our pupils from dilating. Full dark adaptation takes about 30 minutes, and allows a person to see objects that are about 1/3,000 the brightness of the faintest object you can detect PRIOR to dark adaptation. This makes a TREMENDOUS difference in a night out with a telescope. So if you have a neighbor who's an amateur astronomer, please try to ensure that your lighting isn't shining on/at them! Don't contribute to "light trespass".


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