Dark Skies

Astronomy hinges on collecting and analysing light that has travelled from galaxies, stars, nebulae and planets to Earth. This radiation can travel from billions of light years away, and on the final legs of its journey is distorted by the Earth’s atmosphere. While some of this disturbance can’t be avoided (like clouds), other factors such as light pollution can and should be reduced.

When Siding Spring was chosen as an observatory site, it was partly because of how dark the skies were in the immediate area. To help preserve the dark skies, regulations were put in place, restricting the lighting used in nearby towns and buildings within 100 km of the observatory. Over the years, light pollution from cities, coalfields and sportsgrounds has changed the night horizon dramatically. The bright glow created adversely affects astronomers, but can also disorient migratory birds and disrupt animal reproductive cycles. Only the town of Coonabarabran, which has strong ties to the observatory, has had no increase in their sky-glow, reflecting the goodwill of the residents and the success of the Siding Spring Dark Skies Committee.

An image of light pollution hot spots in NSW

A light-pollution map of NSW. The red cross marks the location of Coonabarabran. Image: AAO

Reducing light pollution is easy – it’s as simple as using efficient LED’s for outdoor lighting, not using excessive lighting, and directing the light down towards the ground instead of up towards the night sky. These are all measures that can be undertaken by local councils and residents, and are more cost effective than wasteful lighting. It’s estimated that bad lighting on a global scale costs billions of dollars. Sadly, almost a fifth of the world’s population can no longer even see the Milky Way when they look at the night sky because of light pollution. As of 2015, the Warrumbungles National Park was in a bid to be recognised by the International Dark Sky Association as a Dark Skies Park, which will help to preserve the skies around the observatory for the future.

An image of the horizon as seen from the observatory

Two panoramas of the horizon at night around Siding Spring Observatory. The bottom image
(2014)  shows the increase of light pollution. Image: David Malin

 

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