Arkiv för kategorin 'Light pollution'

It’s about the stars too

Postad i kategorin: CSG, Light pollution, Mining den 18 November, 2015


Arriving at Siding Spring Observatory this morning, we drove into a cloud of fog. The visitor centre was closed and we peered into the milky fog to see if there were any more houses anywhere. “Quiet please – astronomers sleeping” signs tell us as we walk up to a house-like shape. It’s not only a house, it’s staffed and we’re helped to get hold of Peter Small, whom we were here to see. Peter arrives in a big white ute (everyone here drives a big white ute), and takes us to the telescope. Here, we get a rundown of both the observatory, and the local movement against Coal Seam Gas mining.

The man quoted in my last post explained his resistance to coal seam gas as being “all about the water”, but it is about the stars too. Siding Spring was chosen as the location of the observatory – Australia’s largest – in the 1960s because of its dark sky. The Australian National University runs the facility, and as there were too much light pollution in Canberra, where the university is located, the hunt for darker skies began. Siding Spring, situated on the edge of the Warrumbungle National Park, also had the altitude, the (lack of) humidity and the high percentage of clear nights going for it.

It’s the 1,100 m altitude that also accounts for the cloud. It’s quite a view, we’re assured, should the cloud suddenly lift. The observatory is the largest employer in the nearby town of Coonabarabran, which calls itself the Astronomy Capital of Australia, and it began to assert its presence already south of Dunedoo – 150 km away – as we caught sight of a billboard sign featuring Pluto on our drive here. This was part of the Solar System Drive, a scale model of our solar system where the dome of the Anglo-Australian Telescope (AAT) at the observatory acts as the sun. In town, the observatory is also present in the streetscape with murals, telescope stickers in shop windows and the Coonabarabran News Agent is “bringing news to the universe”.

The presence of the observatory also imposes restrictions on the town, which is not supposed to grow. “Coonabarabran is a pretty dark place, perhaps you noticed if you’ve been there at night” says Peter and talks about the regulations in place to protect the dark skies above the observatory. The basic principle is that the light should point down and not spill out upwards. Showing a picture of a street with lighting according to regulation next to a street where they’re not, it is obvious that the regulation lit street is not only darker above, but also much lighter on the ground. “So it’s better for everyone”, says Peter. There are light restrictions within 100 km of the observatory, and the efforts by the host town are evident in the comparative photographs from 1986 and 2014 respectively displayed in the viewing gallery of the AAT. In the recent picture, Coonabarabran is the only place that has not increased its light emissions compared to 1986. In the 2014 picture even Sydney, some 400 km southeast, is visible. And in more recent picture, there is a new bright dot: the Boggabri coalfields. This mine with its 300 workers creates more light pollution than the towns of Gunnedah and Narrabri combined. As being located 120 km away, the mine is outside the regulated zone. Nowadays the observatory tries to be more proactive and works with a proposed mine, which has agreed to design its facilities in accordance with the light regulations.

There is something of a loophole here, since mines or gas wells are not on the list over regulated structures. And the gas wells are a real concern. There are currently around 30 test wells in the Pilliga forest some 50 km from the observatory. They are not in production, Santos who owns them does not have a production license, and the excess gas needs to be either vented, or burnt. And this flare is a significant source of light pollution. It also has do to with the colour of the light. Red light creates more disturbance for the astronomers. The flares from a gas field might force the observatory to close.

Another mining-related issue is dust. In many areas people rely on rainwater which they store in water tanks. Dust covers the roofs and finds its way down to the water and pollutes it. But dust not only risks polluting water, dust also reflects light which causes additional light pollution. Astronomers also fear that corrosive airborne chemicals may harm the telescope mirror.

The telescope is essentially like a big bucket collecting light, Peter explains, and the larger the mirror the more light it can collect. And the darker the sky around it is, the more light from faint and distance light sources it can collect. To protect the night, the observatory supports a bid to have the Warrumbungle area recognized as a Dark Sky Park by the International Dark-Sky Association (I had no idea there is an International Dark-sky Association!).

Peter takes us for a drive on the winding roads around the observatory site which contains 45 telescopes of different sizes. We are especially pleased to see the telescope named after Martin’s long-time hometown Uppsala, which was used to scan for near objects such as comets that might threaten Earth, until its funding was cut last year that is. To wrap things up, we drive to the Skymapper telescope, which during a five-year survey will map the Southern Sky, imaging every section of it 36 times to create a detailed record of more than a billion stars and galaxies. This is also the spot where you would have a superb view of the Warrumbungle national park if it wasn’t for that cloud. As we are preparing to be content with Peter’s word for it, the cloud lifts a little bit, revealing glimpses of a stunning landscape basking in the sun.





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