Anton Vamplew was once the Blue Peter astronomer and he’s since written a number of books on the wonders of the night sky. His current concern is light pollution and he’s here to tell us how we can avoid it here in the mountains!
“One of the biggest problems facing most stargazers today is light pollution. This is simply caused by the vast array of lighting, together with a good dose of industrial pollution, that in the worst cases cause the night to take on an unearthly orange glow. From some places the effect of light pollution can be to virtually wash away any evidence that there is any wondrous starry sky vista lurking hide behind it. Add in a dollop of hazy weather and what you’re seeing is even worse, as the light gets bounced around even more.
Not surprisingly, the worst places for light pollution are major towns and cities, so all you lot sitting in your chalets and apartments in the Alps are probably feeling quite smug right now. You’ve left all that nonsense far behind, and while stargazing was probably not the reason for coming to the mountains, hopefully most of you have noticed how stunning the night sky is.
Even so, there still will be light-pollution around. For example, an annoying bright light from a neighbour’s badly adjusted security light might spoil the night sky view from your balcony. So, in effect, one light can be just as terrible as an entire city when it comes to enjoying the night sky. Wherever you are, the problem is getting worse as towns spread and people feel they need more protection for their homes.
With increasing light-pollution, the grandeur of the night sky has gradually been eroded, as the number of stars you can see decreases. This is all described by something called limiting magnitude – that is the faintest star you can see on any night.
A quick note here about magnitudes before the story continues. When looking into the night sky it’s easy to see that not all stars have the same brightness – some are really sparkly whilst many others look extremely faint. The term we give to any objects appearance in terms of brightness is visual magnitude.
The magnitude system was developed several thousands of years ago by the Greek astronomer and mathematician Hipparchus. He divided the stars into six magnitudes. The twenty brightest stars he could see were classed as magnitude 1, or you can also say “first magnitude”. Slightly fainter stars fell into magnitude 2, and so on right down to magnitude 6, which he classified as the faintest stars you could see with the eye.
In very dark locations (now with better measuring technology than the Greeks!) we know the eye can see stars down to magnitude 6.5-ish. But with more lights around, this can easily be reduced to a handful of only the brightest first magnitude stars – hence, as you increase the light pollution, the sky becomes brighter than the fainter stars.
The biggest casualty is that of the Milky Way, which stretches high over the mountains in autumn. Practically, it has a brightness of around magnitude 4.5. This makes it accessible from darker suburban locations, but washed away from places with more street or general lighting. By definition, more people live in towns and cities; therefore there are an increasing number of people who have never seen the Milky Way.
Of course, if you are hampered by light-pollution, you only need to take a short walk or hike into the mountains to find somewhere truly dark – hopefully with a nice bar to keep warm in nearby! However, just say you’re intent on not leaving the chalet. There are still some things that can help lessen the effects of light-pollution for you.
Firstly just try repositioning yourself! If there’s a nearly street or security light, try and find a place that is hidden from its view, maybe by either moving closer to a fence or wall. You’ll be genuinely surprised by how much that can change what you are able to see.
You will also improve things by making sure your eyes are fully dark-adapted before you go outside. Just get a red-light torch ready (these don’t affect your eyes when they’re adapted), turn off the lights and sit in the dark for fifteen minutes. What fun that can be! Also, keep the apartment / hotel lights off so they don’t light up your viewing place once outside. People may think you’re going mad, and hey, that may be the truth, but you’ll be having the last laugh as you count the 3,000 or so stars that you can see with your wonderfully dark adapted eyes. Meanwhile they’ll be squinting up at the night unable to see much at all – you know the sad sort.
Finally, how friendly are you with your neighbours? It may be their security light that streams into your chalet or onto your balcony. If you find it difficult to bring up the subject, then invite them round for a cup of warming broth and take them out to look at the night sky from your point of view. Maybe they’ll get the message themselves when they see a lighthouse shining in their face!
Good luck, and remember, enjoy the night responsibly.