International dark sky places: the other kind of black holes
If you want to escape light pollution completely, only an International Dark Sky Park or Reserve will do. Science writer Jamie Carter presents the definitive guide.
European dark skies. Image credit: NASA
There is a rule of thumb for stargazers and amateur astronomers after an inky black dark sky: go where people are not.
When the Moon is down, if you move from a light polluted city where you can see +4 magnitude stars to somewhere away from the city where +6 magnitude stars can be seen, the difference will amaze you.
Great advice, but better is a ‘bucket list’ of places where night skies are protected.
Cue a network of Dark Sky Parks and Dark Sky Reserves across the globe that tackle light pollution to preserve the night sky.
Protecting night skies
Sites designated by the Arizona, USA-based International Dark-Sky Association (IDA) are working hard to protect night skies, often by ensuring any lights in the area are shielded and don't contribute to sky-glow.
And while their sites don't constitute an exclusive list of dark sky destinations for amateur astronomers seeking darkness, it’s a great place to start.
“The program is not just about recognising places that are dark, it’s also about recognising the efforts of people trying to keep them that way,” says John Barentine, IDA DarkSky Places Program Manager, and author of The Lost Constellations.
“But the degree of darkness is one of the absolute minimum requirements.”
Park vs reserve
The IDA-certified areas are largely centred on existing national parks.
Remote, unpopulated areas tend to get International Dark Sky Park designation (31 in total), while more populated areas with a dark 'core' are termed International Dark Sky Reserves (there are now 10 worldwide).
“Towns and cities a couple of hundred kilometres away aren’t trivial, but they only contribute to a sky-glow on the horizon,” says Barentine.
“For protection of the sky brightness at the zenith – the point above your head and often the darkest part of the sky anyway – means you have to concentrate on reducing lighting in communities immediately around the park.”
Gold, Silver & Bronze skies
Are some places darker than others?
“We have this Gold, Silver and Bronze system, which applies to both the parks and reserves,” says Barentine about the quality of the night sky within, though he admits that it's a mix of objective and subjective data.
Sky quality meters are used to measure the darkness, but the IDA also uses anecdotal observations of the aurora, faint satellites and meteors, Gegenschein (a faint brightening on the ecliptic, usually opposite the Sun), zodiacal light, and the quality of local night-sky photography.
“It’s a holistic approach because you can’t get to every corner of every park,” says Barentine, who also consults local astronomy clubs.
Dark Sky Discovery Sites
“We’re getting to a level where the dark skies are getting well known, which is driving the Dark Sky Discovery Sites and the IDA’s dark sky places,” says Barentine.
However, the philosophy behind Dark Sky Discovery Sites is different to the IDA; it's about easy access to public land that’s largely free of light.
Our tip? Swerve the ‘Orion’ class locations – where only the seven main stars in Orion need to be naked-eye visible – and choose the more remote 'Milky Way’ locations instead.
The darkest skies
Want to find the very darkest spots in the world?
“Take a look at photos of the Earth at night taken by satellites, which are now at sub-kilometre resolution,” says Barentine, who also suggests checking out citizen science star-count projects the Globe At Night and the Loss Of The Night Network, while the Dark Sky Meter app for phones makes a brightness measurement, with all results plotted on maps.
So next time you’re in an International Dark Sky Park or Reserve or, indeed, anywhere that stargazers might gather, take a reading and upload it.
More elusive than ever as towns grow and poorly-shielded LED lights get more popular, the darkness needs our help
International Dark Sky Parks & Reserves in the UK
Scotland: Galloway Forest Park
Remote, empty and a candidate for the UK's darkest-possible night sky (Sky Quality Meter (SQM) scale readings go from 21 to 23.6), Galloway Forest Park International Dark Sky Park was the very first of its kind in the UK.
About two hours drive south of Glasgow, or north of the Lake District, its 78,000 hectares make for a vast sanctuary for stargazing (it's also an UNESCO Biosphere and even has a cast of four Biosphere Dark Sky Rangers).
Get to a super-remote location like Loch Riecawr and skyglow is non-existent; you're surrounded by forest.
Another good location is Clatteringshaws Loch in the south of the park (look out for the Rosnes Benches), which has a visitors centre, while there's also an observatory that runs stargazing events, as does the Forestry Commission.
England: Exmoor National Park
Designated as a silver-tier International Dark Sky Reserve back in 2011, one of the best places within Exmoor National Park to go stargazing is Wimbleball Lake Country Park, a Dark Skies Discovery Site with 'Milky Way' status.
Another top location is Dunkery Beacon, the second highest point in the South West, from where you can enjoy a stunning 360° view of the skies above Somerset.
The 520m-high summit is less than a kilometre from the car park. Dunkery Beacon Country House Hotel has a Newtonian telescope and an enthusiastic owner.
Wales: Brecon Beacons, Elan Valley & Snowdonia
With three IDA-certified areas, Wales has more protected sky, as a proportion of its landmass, than any other country.
In, fact, there's something of a dark sky corridor stretching from the easily accessible, silver-tier Brecon Beacons International Dark Sky Reserve (go for the emptier western area, near Crai or Usk Reservoirs, though there are many great locations including Brecon Beacons Observatory) through the Elan Valley Estate International Dark Sky Park (also silver tier) and on to the silver-class Snowdonia National Park International Dark Sky Reserve.
“Elan Valley is considerably smaller than the national parks in the UK,” says Barentine of this privately-owned area.
“Perhaps we’ll start working on the neighbouring communities and create a large Dark Sky Reserve centred on the Elan Valley.”
If you're visiting Elan Valley, The Spaceguard Centre is close-by.
England: Northumberland & Kielder
Northumberland National Park and Kielder Water & Forest Park together make up this vast two-part International Dark Sky Park in northern England.
Comprising 1,500km of public land, gold-star status has created new stargazing-centric tourism.
The Sky Den treehouse has a telescope, you can go 'glamping' with Wild Northumbrian Stargazing and astronomers from Kielder Observatory, while Blacksmiths Cottage organises bespoke group stargazing evenings with a local astronomer, as well as telescope hire.
And, you never know, at this latitude the aurora borealis may even pay you a visit …
Read all about the Dark Sky Sites of Wales in the April 2016 issue of BBC Sky at Night Magazine, out 17 March.