The Astronomer's Enemy

2010-05-17 00:00

There's one problem with Urban astronomy, and it's a big one. It is the reason so many historical observatories, places where great discoveries were made and the foundations of modern astronomy were set down, have been shut down and even demolished. That problem is light. Modern cities pump so much light into the sky that many of us have never actually seen a night sky at all. Ask somebody what colour the sky is at night and they'll confidently assert "Black, of course!". Which just goes to show when last they actually looked up. The night sky in the city is navy blue in the suburbs, and dull orange in the city proper, and shines bright enough to completely extinguish all but a handful of the brightest stars. If we happen to glance up, we see nothing at all. The sky is boring, and not worth watching.

But try this experiment to see just what you're missing, and what our ancestors took for granted: Wait for a moonless night, then get in your car. Drive out of town, taking a back road. You want to get somewhere very remote, with no traffic around you and no lights visible anywhere (You might have to drive quite far, so pack a flask of coffee!). Once you've found your spot, stop the car and look out the window. You will see a breathtaking display - the sky itself as black as ink, and an astonishing spray of stars powdering the whole sky. Admire it a bit, enjoy it, and then when you're ready for the REAL show to start, turn off your lights. That's the headlights, the courtesy light, everything. Then get out of the car. It's a breathtaking experience, and all by itself will give you a new perspective on your place in the universe.

The biggest surprise we all get is that, after about 15 minutes or so, your eyes adapt to the point where you can see by starlight well enough to take a short walk and find your way back to the car. And bear in mind that this is what our great-grandparents took for granted every single night!

Light pollution is taken very seriously by astronomers (both professional and amateur), and some environmentalists, and there are a number of activist groups fighting to get something done about it. There are even towns with by-laws forbidding outside lights after certain hours at night, and their astronomers are very fortunate indeed. But what can the rest of us do?

Firstly, we can minimise the effects of local lighting. Find a spot in your yard where the fewest lights (street-light, neighbour's security floodlight, your bathroom light, etc) can reach you. Put up screens, or plant hedges, to block the remaining lights. In this way, you create a small space which is much darker than your surroundings. Simply spend a few minutes in there, and you'll find your eyes adapting in the same way they did in our experiment above, and you'll find a lot more stars become visible. Unless you're truly in the heart of the city, you should be able to see all the significant stars of all the important constellations, and that's already enough to give you plenty to watch for the rest of your life. If you can see that much, then you can begin to learn the constellations, and you will easily see the 5 classical planets (Mercury, Venus, Mars, Jupiter and Saturn - these five planets are brighter than most stars).

Secondly, conditions are never bad enough to blot out the moon -- it's visible during the day which shows that even the sun isn't bright enough to hide it. While the naked eye doesn't reveal much of interest (apart from the phases, and some mottled patterns), even the smallest of binoculars will reveal craters, mountain ranges, and a wealth of other detail which you can spend years studying and getting to know (If you're interested in that sort of thing!)

So this is what Urban Astronomers do. We deal with Light Pollution. in the day, some of us campaign to do something about it, but the rest of us simple put up with it, and find ways to pursue our hobby in spite of it. It's a challenge, but it sure beats having to plan a major expedition every time you want to view from a decent dark-sky site!

Visit The Urban Astronomer

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