Saturday, February 5, 2011

Dark Skies

Sark - Where the bloody hell is it? It's a Channel Island, about 350Kms from Paris and 300Kms from London. The island of Sark has become a 'Silver Tier Dark Sky Park'. This means that the visual limiting magnitude is between 6.0 to 6.7, there are other criteria, this is the simplest. The rating is endorsed by the International Darksky Association (IDA) and it was achieved by a resident of Sark that measured and assessed the every light fitting on the tiny island 5.5 sq ams. The island had a head start because there are no cars, so no street lights. The Government of Sark was ready to accept that with the rating comes conditions that will retain the island as Dark Sky Park. The island of Sark is not the only such park, the website of the IDA lists others, some with higher ratings.

I think back to my first ventures in Astronomy, and I can recall dark skies from suburban Sydney. In the night sky I distinctly recall seeing both the Large and Small Clouds of Magellan and the bright band of the Milky Way. I'd say the clouds of Magellan were still visible to the unaided eye as recently as the 1970's. These days the Southern Cross (Crux) appears to be fading and certainly the Coal Sack is almost impossible to discern from Sydney.

The year of 2010 was interesting for Astronomy around Sydney. The Beames Observatory at Linden, in the Blue Mountains gained a Heritage Listing. This included 40 hectares of bushland to assist in preserving dark skies. It is also now three years since the National Trust registered as a Heritage Item both the Night and Day sky over New South Wales. What's happened since - not much