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International Dark Sky Places

June 14, 2012 4 comments

The global family of International Dark Sky Places – areas with stunning night skies and exemplary lighting controls to preserve those skies – has grown again recently, with the addition of some huge parks and reserves. There are currently (as of June 2012) 18 places around the world that satisfy the International Dark-sky Association‘s (IDA) requirements.

The Church of the Good Shepherd, Aoraki Mackenzie IDSR Image by Fraser Gunn

I’ve been lucky enough to visit 12 out of these 18 incredible places, including the two most recent additions to the IDA family, NamibRand Nature Reserve in Namibia, and Aoraki Mackenzie in New Zealand, both of which have been awarded International Dark Sky Reserve status this year.

The IDA has three different designations: International Dark Sky Park (IDSP), International Dark Sky Reserve (IDSR), and International Dark Sky Community (IDSC).

IDSPs are areas of public land that are near-empty wildernesses, and which have enacted strict controls of outside artificial lighting throughout the entire park. There are currently ten IDSPs.

IDSRs are large areas centred on a dark sky core, a significant area – an observatory, say – in need of protection against light pollution, and a 15km-minimum buffer zone around that core, encompassing surrounding communities. The communities in the buffer zone have lighting controls that help minimise light pollution in the core area. There are currently four IDSRs.

IDSCs are communities – cities, towns, villages, islands – that have enacted exemplary lighting controls to limit the spread of light pollution into their night skies. There are currently four IDSCs.

The following table has some information about the various International Dark Sky Places:

Name Location Park Area Designation Year Designated
Aoraki Mackenzie New Zealand  4300 km2 Reserve  2012
Big Bend National Park Texas, USA  3242 km2 Park  2012
Borrego Springs California, USA  110 km2 Community  2009
Cherry Springs State Park Pennsylvania, USA  4.3 km2 Park  2008
Clayton Lake State Park New Mexico, USA  1.9 km2 Park  2010
Exmoor National Park England, UK  692 km2 Reserve  2011
Flagstaff Arizona, USA  255 km2 Community  2000
Galloway Forest Park Scotland, UK  780 km2 Park  2009
Geauga Observatory Park Ohio, USA  4.5 km2 Park  2011
Goldendale Observatory State Park Washington, USA  0.2 km2 Park  2010, provisional
The Headlands of Emmet County Michigan, USA  2.2 km2 Park  2011
Homer Glen Illinois, USA  58 km2 Community  2011
Hortobagy National Park Hungary  800 km2 Park  2011
Mont Megantic Quebec, Canada  5000 km2 Reserve  2008
NamibRand Nature Reserve Namibia  1722 km2 Reserve  2012
Natural Bridges National Monument Utah, USA  31 km2 Park  2006
Sark Channel Islands, UK  5.4 km2 Community  2011
Zselic Landscape Protection Area Hungary  90.4 km2 Park  2009

 

Saint Helena Dark Sky Island

April 13, 2012 6 comments

This blog post is a copy of one which I wrote for the Guardian Science blog, posted there on 13 April 2012.

The small South Atlantic island of Saint Helena is about as remote as any place on Earth gets. It lies 2000km from Africa and 3000km from South America, and I’m heading there for eight days this month to carry out a dark sky survey.

Saint Helena, 1815

This survey will allow me to determine the quality of the night sky above Saint Helena – the darkness of the sky, but also the clarity of the stars – in anticipation of the island becoming an International Dark Sky Place, a designation awarded by the International Dark-sky Association (IDA).

Light pollution is a common problem for astronomers living near cities; a familiar orange glow drowning out the light from all but the brightest stars in the night sky. With the spread of suburbia there are increasingly fewer places where stargazers can enjoy an unspoiled dark sky, but the further you travel from urban areas the more stars you will see, and Saint Helena as about as far as it’s possible to be from the next town.

Under such dark skies the Milky Way can be seen stretching from horizon to horizon in an arc overhead, and the heavens are studded with thousands of stars and many nebulae, including the dramatic Magellanic clouds not visible from far northern latitudes. Indeed its location at 16° south of the equator means that virtually every constellation is on display at some time throughout the year.

Small and Large Magellanic Clouds, Akira Fujii/Davidmalin.com

Saint Helena’s Astronomy Heritage

Saint Helena has long been used by astronomers as a site for making important observations. Edmund Halley – he of comet fame – visited the island in 1677 to catalogue the southern stars and observe a Transit of Mercury. The following century, in 1761 Neville Maskelyne, later to become Astronomer Royal, came to observe a much rarer Transit of Venus. (Incidentally, a Transit of Venus occurs this year on 5/6 June, only the fifth to occur since 1761, and the last for over 100 years).

The Dark Sky Survey

During the survey I’ll be using a Sky Quality Metre (SQM) to assess the brightness overhead. This device measures sky brightness in units of magnitudes per square arcsecond (magnitudes are a measure of brightness, the lower the number the brighter the sky; square arcseconds are a measure of area, where one arcsecond is 1/3600 of a degree).

In my back garden in the suburbs of Glasgow the SQM reads around 18 magnitudes per square arcsecond; in the centre of Glasgow it might read 16. The darkest readings come from remote places like Galloway Forest Dark Sky Park where 21.7 isn’t uncommon. In the very darkest places the limit of the device comes from the brightness of the stars overhead, and so you can’t expect readings much darker than 22.0 even in sites free of light pollution.

As well as these SQM readings I’ll be estimating the naked-eye limiting magnitude (NELM) of the night sky above Saint Helena. This basically involves looking for the faintest star I can see and reading its magnitude from a star atlas. In a city the NELM might be 3 or 4; in Galloway Forest Dark Sky Park it might reach 6.5 or even 7, where the only limit to what you can see is your eyesight.

Dark Sky Tourism

So why go to all this trouble? Well, an extensive dark sky survey is just one of the criteria expected of an International Dark Sky Place. Once this survey work is carried out, along with a lighting audit and adoption of new lighting codes on the island, the IDA might confer this status on Saint Helena. And the drive for all this work? Tourism. At the moment Saint Helena’s tourism is based almost exclusively on Napoleon’s exile there between 1815 and 1821. The Island also has several hundred species of flora and fauna which only found on this remote Island and is steeped in history from the Age of Discovery when it was a crucial staging post for sailing ships. The island attracts around 1000 visitors per year.

The main difficulty for the prospective visitor is travel to the island. The only way of getting there right now is on the RMS Saint Helena, on a six-day ocean voyage from Cape Town, something that may deter all but the most determined traveller. Come 2015 however, the island will have its own air strip, making it more accessible and tourism visits more regular.

The Saint Helena Tourism Association hopes to attract visitors with the prospect of the stunningly dark skies above the island. The concept of dark sky tourism has been growing over the past few years. There are currently 16 International Dark Sky Places recognised by the IDA, including three in the UK: Galloway Forest Dark Sky Park, Sark Dark Sky Island, and Exmoor Dark Sky Reserve. These sites are seeing an increase in visitor numbers in the dark winter season as keen stargazers, inspired perhaps by Prof Cox, flee the bright city lights for darker skies.

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