Alps Starry Skies: A Heritage to Save from Light Pollution
It is fascinating to stand atop a skyscraper at night, watching the city lights glow below. It is also fascinating to stand upon a 2600 m high mountain in the alps, and watch city lights glow below. In the past I have experienced and enjoyed this fascination on many Mountainbike Nightrides or while Alpine Skitouring, and I still do. The area around Innsbruck, where I live, has a reputation for providing stunning views from many peakviews around the city. Same goes for Davos or Chamonix.
In Winter, many people in the Alps, do after-work night skitouring to their loved peaks, enjoying the fantastic scenery in the valleys below. It’s a huge culture, and city lights are some part of it.
Resting on a peak after the ascent, just turn towards the familiar lights below, and feel a bit safer for the way back home. Or connect with civilisation: On some occasions, during many nights of imaging at 2000 m high, totally lonesome volcanic ridges of La Palma, Canary Islands, I felt so exposed to space or like being on Mars, that I sometimes walked over to the next ridge, to get a view back to the cities far below.
But as always, there is another significant side to glowing city lights, and it comes with an environmental price tag: light pollution (aka “wasted light” or “junk light”). Simply put, it is scattered light where it is not needed – in our case: the sky above. wow.
Some of my astronomical short films like “Urban Mountain Sky” or “Adventures after dark“, play with and illustrate the fascination of urban lights against the mountains very well, or the absence of it and therefore stunning unspoiled views of truly dark skies (“Island in the sky” or “Astronomer’s paradise“).
Living in the Alps however, I always felt safe about light pollution, which I thought to be an issue everywhere else. But I was wrong and I wasn’t alarmed about the signs so much until recently.
It’s also that we are a bit spoiled with starry skies in the Alps. Regardless if it was during transparent winter nights, clear skies of autumn, or summertime when a storm front washed the sky clean… Since we were kids, we could and still can enjoy stunning starry nights over the mountains – even near alpine urban areas like Innsbruck or Brixen. This makes for a deceptive feeling that all is well with our night sky above the Alps. And of course, compared to areas like the German Ruhrgebiet or Northern Italy which suffer from heavy light pollution, we still do have some pretty amazing starry sky nights in the Dolomites, Tyrol or Bavaria. Once in a month or two, there’s always a night, where stars and the Milky Way sparkle from the sky above in a way, reminding me of the dark skies seen in the Atacama desert. (Sky transparency however can never be as excellent in the Alps as in the Atacama, with its ultralow average 5% humidity. Low humidity = excellent seeing of stars).
Taking advantage of weather with good sky transparency (reduces light scattering), low-light astrophotography knowledge and high view points, I managed to capture the Milky Way above Innsbruck many times. Although post processing is tricky for bright city shots with lots of Sodium- and increasing LED color cast.
Of course, the Milky Way above a city is quite unique for a city in the Alps that big, and even surprised TWAN founder Babak Tafreshi on the first of several imaging trips to Innsbruck, where we joined forces. My film “Urban mountain sky” even shows constellation Orion during dawn from the famous Hungerburg cable car station – only 200 m above the bright city.
Again, all this gave me a deceptive feeling that all is OK with the starry sky above the Alps. But that feeling persistently weakened recently, when inversion layers came into play and stayed for quite a while above our heads in winter, when the mostly V-shaped alpine valleys fill with smog resulting from too much transit traffic, as well as industry and household emissions, severely amplified by temperature inversions. Colder, polluted air is then trapped below a layer of warmer air with no exchange between layers. Besides a multitude of health problems due to increased levels of fine particles in the air, hazy or foggy temperature inversion layers boost light pollution, backscattering light, bouncing it within the inversion layers.
The combination of bright city lights and inversion weather makes one feeling like being trapped in a “light cage”. As much as possible, and if there is no overcast above the inversion layers, I then hike up mountains and get out of the polluted layers – mountains are my skyscrapers.