With summer coming to an end in the British Isles we start the return to the dark skies of autumn and winter. Depending on where you are in the country you will have been without truly dark skies for many weeks, maybe even months, as summer evening twilight lasts throughout the night during the summer.
This all-night-long twilight is almost gone throughout the UK, indeed anywhere on the mainland UK can see astronomically dark skies around 1am at the moment. Only the furthest north outpost of the British Isles still doesn’t have that opportunity.
On the island of Unst, the furthest north of the Shetland islands, lies the UK’s furthest-north town, Skaw, at 60°49′N and 00°47′W. This tiny village will see astronomical darkness return at 0043 on 24 August, lasting only 46 minutes until at 0129 the sun’s light begins to creep into the sky again.
The last time that astronomical darkness was seen at Skaw was on 18 April, over four months ago! Indeed this settlement is so far north that between around 13 and 29 June each year they never get out of civil twilight, meaning that the sky’s bright all night long!
Compare this with the furthest south town in the British Isles, Saint Clement in Jersey, in the Channel Islands. Astronomical darkness returned to Saint Clement on 4 July this year, having been absent since 8 June; only four weeks without true darkness!
Such is the effect of differences in latitude that these two settlements, separated by 1299 km, have such hugely different seasonal swings between summer and winter.
Last Saturday night I visited the site of the soon-to-be-open Scottish Dark Sky Observatory. Sitting on a hill top in Craigengillan Estate near Loch Doon, this stunning new public observatory lies on the edge of Galloway Forest Dark Sky Park, under some of the darkest skies in the UK.
At the moment the observatory is still under construction, and is due to open in a few months time, at the start of this winter dark sky season. It will be open to the public and school groups for day-time and night-time visits.
The site itself is wonderful, and the observatory is nestled amongst the graggy hill tops east of Ness Glen, just south of the small town of Dalmellington on the A713.
The observatory will include a fully robotic 20” Corrected Dall Kirkham telescope in a 5m dome, operated from either of two control rooms; a roll-off-roof observatory with a 10” SCT for a more hands-on, out in the open observing experience; a multi-purpose lecture room served by a toilet and kitchen and an “outdoor classroom” in the form of an elevated observing deck from which to enjoy the experience of naked-eye observation. Facilities will be provided for amateur astronomers to set up their own equipment and have access to the toilet and kitchen facilities. It will be open to the public, amateur astronomers and to schools and universities, with the aim of inspiring people of all ages and all backgrounds with a sense of wonder at the vastness and beauty of the heavens and the revelation of man’s place within the universe.
The Observatory was the brain child of Craigengillan Estate owner Mark Gibson and the Renfrewshire Astronomical Society (RAS). A member of the RAS, Colin Anderson, is an architect and he designed the buildings. It’s a tribute to Mark, Colin, and others in the RAS that this project is even possible, and I for one cannot wait to observe from their incredible new observatory.
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.
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|
I recently attended the Third International Starlight Conference held by the Starlight Initiative near Lake Tekapo, New Zealand. The conference brought together a huge range of specialists who seek to limit the excesses of light at night, and the venue sat in the recently-announced Aoraki / Mount Cook International Dark Sky Reserve (IDSR) in New Zealand’s stunning south island.
The beauty of the night sky from somewhere like Tekapo is astounding, and the IDSR status will help keep it that way, limiting the amount of lighting that can spill into the sky from the surrounding communities. Under such starry skies it’s easy to understand why we’d want to protect them, but for most of the population of the planet starlight is becoming increasingly more elusive.
To help emphasise the importance of a dark starry sky the conference looked to build upon a document written at the first Starlight Conference in La Palma, in 2007, the Starlight Declaration in Defence of the Night Sky and the Right to See the Stars.
The Starlight Declaration states:
a. An unpolluted night sky that allows the enjoyment and contemplation of the firmament should be considered an inalienable right equivalent to all other socio-cultural and environmental rights. Hence the progressive degradation of the night sky must be regarded as a fundamental loss.
b. Knowledge—armed with education—is a powerful vector that can heal the growing rift between today’s society and science and contribute to the advancement of mankind as a whole. The dissemination of astronomy and of the scientific and associated cultural values should be considered as basic contents to be included in educational activities.
d. Control of obtrusive light must be a basic element of nature conservation policies since they impact on several species, habitats, ecosystems, and landscapes.
c. Protection of the astronomical quality of areas suitable for the scientific observation of the Universe must be given priority in national and international scientific and environmental policies.
e. The intelligent use of artificial lighting that minimizes sky glow and avoids obtrusive visual impact on both humans and wildlife should be promoted. This strategy would involve a more efficient use of energy so as to meet the wider commitments made on climate change, and for the protection of the environment.
f. Tourism, among other players, can become a major instrument for a new alliance in defence of the quality of the nocturnal skyscape. Responsible tourism, in its many forms, can and should take on board the night sky as a resource to protect and value in all destinations.
Necessary measures should be implemented to involve all parties related to skyscape protection to raise public awareness—be it at local, regional, national, or international level—about the contents and objectives of the International Conference in Defense of the Quality of the Night Sky and the Right to Observe Stars, held in the Island of la Palma.
Dated 20 April 2007, La Palma, Canary Islands, Spain
The Bortle Scale is a useful way of estimating your sky brightness, i.e. to what extent light pollution affects your view of the night sky. By going outside on a clear moonless night and recording what astronomical objects you can see you can assign a Bortle Class rating to your observing site.
I have used the Bortle Scale to assess night sky quality many times, and always felt the lack of a handy flow chart to lead me through it. So I made one. Enjoy. (You can also download the pdf version.)
PS The content of this chart assumes some prior knowledge of astronomy, but any of the terms used are easily google-able.
In case you haven’t heard the BBC are running another series of Stargazing Live starting on Monday 16 January for three nights. Each hour long programme will be presented by Professor Brian Cox and comedian Dara O’Briain, and will feature a wealth of information about what’s visible in the night sky.
This series will focus on light pollution, and the benefits of a dark sky.
On Wednesday 18 January, Dulverton in Somerset [in Exmoor Dark Sky Reserve] will attempt to become one of the first towns in the UK to have every single one of its lights turned off at the same time, as part of a Stargazing Live demonstration showcasing the beauty of a night sky free of the effects of light pollution.
There are 177 street lights in Dulverton making the night sky significantly brighter and making it much harder to see the stars. At roughly 8.15pm on Wednesday (or at the sound of a unique set of church bells), the Stargazing Live team want every single person in Dulverton to turn off every single light in the town, giving people in the area the unique chance to take in the wonders of the night sky free of the effects of light pollution.
To support this series, and encourage people to get out and look up, the BBC are sponsoring hundreds of events around the country, from planetarium shows to star parties, from lectures to observatory visits. You can find out what’s on near you on their events page.
To find out more about the shows visit their website, where you can view images, download their excellent star guide and activity pack, listen to some audio guides, watch “how to” videos, and take part in live web chats. You can also follow the series on Twitter using the hashtag #BBCstargazing.
Once again the Campaign to Protect Rural England and the British Astronomical Association’s Campaign for Dark Skies are running a UK-wide star count programme. This year’s event takes place between 20-27 January 2012. On any of these nights the skies will be dark enough to begin your star count by 7pm.
To make your own observations for Star Count 2012 find Orion in the sky and count how many stars you can see within the rectangular boundary formed by the four brightest stars in Orion. Those boundary stars are called Betelgeuse, Bellatrix, Rigel and Saiph.
You should count the three belt stars – Alnitak, Alnilam, and Mintaka – plus any other stars that are visible. The above star map shows around 40 stars within that boundary. If you can see that many stars then you’ll be in one of the darkest places in the UK. For most of us we’ll count far fewer stars than that. People in very bright urban areas may only see the three belt stars.
UPDATE: I should have mentioned that the CPRE will accept observations from anywhere in the UK, not just England.
Hilariously, I have been “quoted” in a fictitious article on the website The Spoof. This article boasts the headline: “London Borough Of Ealing Declared International Dark-Sky Reserve”!
The piece continues:
‘London is an international centre of excellence for numerous endeavours,’ explained Mayor of London, Boris Johnson. ‘It was total madness that Londoners had to travel to the mountains of Chile or to Exmoor, wherever they are, to get a decent view of the night sky.’
So the author(s) of the piece know their stuff: the Atacama Desert in Chile is widely recognised as one of the very best places for stargazing on the planet, while Exmoor became an International Dark Sky Reserve in November 2011, following on from Galloway Forest Dark Sky Park in 2009, and Sark Dark Sky Island in 2010.
The article introduces me as:
UK astronomer Steve Owens, chair of the IDA‘s Dark Sky Places Development Committee
again true, but not nearly so widely known. They must really have done their homework on this story. They then put words in my mouth that are entirely reasonable:
‘To be declared an International Dark-Sky Reserve,’ he explained, ‘an area must possess an exceptional or distinguished quality of starry nights. Light pollution from conurbations is the most significant barrier to this aspiration, and areas in London possess quite exceptional challenges in that respect.’
Ha! Very true. Then the article continues:
As part of the bid for Reserve status for Ealing, street lights were disabled within a ten mile radius… In addition, local byelaws were passed to enforce the use of blackout curtains after dark within the Reserve area. Car headlights and other sources of light, necessary to facilitate travel, were required to be red in order to not affect night vision.
From now on my analysis of this article might read as somewhat po-faced, as I point out their errors, but it does at least allow me to talk a little bit about what it means to be a Dark Sky Place.
The IDA doesn’t require the extinguishing of all street lights, nor black out curtains, nor red car headlights. All nice ideas though, from an astronomical point of view. Just not very practical.
The article then quotes several fictitious Londoners:
‘Since the changes, I have been almost constantly working outside at night,’ said emergency paramedic and ambulance crewperson, Ursula Major. ‘I often point out the constellations to distract RTA and other casualties from their injuries.’ [actually, studies have shown no connection between reduced light at night and RTAs.]
‘Sometimes,’ admitted Leo Regulus, an unemployed young person from Boston Manor, ‘I stop when lootin’ from Ealin’ Broadway ta wunda at the splenda of the Miwkey Way. Last week,’ he continued, ‘I even went back ta Argos ta nick a Newtonian reflecta telescope, init.’ [similarly, there is no good evidence that reduced light at night increases crime.]
Astronomers from across the UK have visited Ealing to avail themselves of its crystal clear view of the heavens. ‘Many initially complained about mugging and the loss of equipment,’ admitted sergeant Izar Bootes from the Metropolitan Police, ‘but the ability to repurchase their kit, or better gear, at Leeland Road market on Saturday mornings has more than compensated for such inconveniences.’ [see above]
Even everyone’s favourite astronomer Prof Brian Cox gets a mention:
The quality of the sky over Ealing means that key astronomical features are clearly visible for the first time in over two centuries. The police have been inundated by calls from anxious residents, worried about the appearance of strange white dots in the night sky.
‘It looks like that Brian Cox bloke was telling the truth, after all,’ said one amazed Northfields resident.
Make sure you read the whole article, but remember: the London borough of Ealing isn’t really an International Dark-Sky Reserve!
I’m heading up to Orkney for two weeks to run a midwinter astronomy festival. I love Orkney, and the chance to visit there in the darkest of the year is a real treat. For astronomers the long winter nights in Orkney have a lot to offer. It’s not just the relative absence of light pollution above Orkney, but also the fact that in the weeks around midwinter there are over twelve hours of pitch blackness between astronomical twilights.
The full programme of events is here, and I hope to blog about a few of my activities too.
The programme is funded by an STFC Science in Society Grant
Astronomy tourism is a burgeoning field – luckily for me, as it’s how I make a living! – with city-folk now starting to make the effort to travel to places with darker skies, in the hope of seeing things that simply cannot be seen from the orange glare of a town sky.
Galloway Forest Dark Sky Park, which I helped establish in 2009, has seen a lot of this dark sky tourism trade, due to its high profile in the media, but many other places around the country – Sark in the Channel Islands, and Exmoor National Park to name but two – have followed suit, hoping to attract the stargazing crowds.
And as more and more people come out of the city for a stargazing weekend under dark skies it’s becoming clear to me that there’s a real appetite for seeing the Milky Way and other elusive dark sky objects. It’s almost become something to put on your “bucket list”: see a wild lion in Africa; fly in a hot air balloon; see the Milky Way.
However there are lots of other amazing astronomical objects visible under a dark sky so here is the first installment of my top-ten “Dark Sky Bucket List”.
1. Milky Way
Our “island universe”, a spiral disk of hundreds of billions of stars, appears in our night sky as a band of grey light arching overhead. From town centres the Milky Way is invisible, lost in the orange glow, but as you move out into suburbia you might start to see traces of it, looking directly overhead. According to the Bortle Dark Sky Scale, under suburban skies (Bortle Class 5) “[the] Milky Way is very weak or invisible near the horizon and looks washed out overhead”, while under rural skies (Bortle Class 3) “[the] Milky Way… appears complex” with structure – dark clumps and bands – set within the grey light. Under perfect conditions (that probably aren’t found anywhere in Europe) of Bortle Class 1, “[the] Scorpius and Sagittarius regions of the Milky Way cast obvious shadows on the ground”. The best we can hope for in the UK – which you might just get in the darkest heart of Galloway Forest Dark Sky Park – is Bortle Class 2 which reveals “[a] highly structured… Milky Way”.
2. Countless stars
Although our Milky Way galaxy contains hundreds of billions of stars, only the closest ones to the Sun are visible as distinct dots in our night sky. From a city sky you would be lucky to see a couple of hundred stars on any clear night – the brightest ones that make up the constellation patterns – but move to somewhere darker and more stars will be visible. Once you get to very dark skies the only limit on how many stars you can see is your eyesight. Assuming you’ve got good eyesight thousands of stars will be visible under a dark sky. The Yale Bright Star Catalogue lists all stars brighter than magnitude 6.5, the approximate limit of human vision, and that list contains over 9000 stars, so if you’re at a dark site (Bortle Class 3 or better) you’ll see around 4500 stars (as you can only see half of the sky at one time).
3. Andromeda Galaxy, M31
The Andromeda Galaxy is our nearest BIG neighbouring galaxy. It lies 2.5 million light years from the Milky Way, and contains even more stars than our galaxy. Even still, it appears as only a small grey smudge in the night sky. From bright city skies (Bortle Class 8) the Andromeda Galaxy is “barely glimpsed by an experienced observer on good nights”, while in bright suburban skies (Bortle Class 6) it is “modestly apparent to the unaided eye”. As you head to darker skies though, Andromeda becomes even more apparent, until under rural skies (Bortle Class 3 or better) you will see it as a very obvious smudge amongst the clamour of stars. Andromeda is relatively easy to find using the constellations Cassiopeia and Pegasus as signposts. Using the W-shaped Cassiopeia, take the right-hand V of the W shape as an arrow that points to the bright star Mirach, or β Andromedae, which sits in the middle of a slightly curved line of three stars, with Alpheratz (α Andromedae) on one side and Almach (γ And) on the other. Go perpendicularly “up” (back towards Cassiopeia) from Mirach to a much fainter star u Andromedae, and then continue the same distance again to find the Andromeda Galaxy.
4. Triangulum Galaxy, M33
Far more elusive than the Andromeda Galaxy is the Triangulum Galaxy, M33. Indeed it is so elusive under anything except near-perfect dark skies that it is used as the benchmark for judging how dark your sky is. It is only visible to the naked eye under Bortle Class 4 or better. At the suburban/rural transition (Bortle Class 4) it is “a difficult averted vision object, only visible when higher than 55° “. Under rural skies (Bortle Class 3) it is “easily visible with averted vision”, but it’s only at truly dark sky sites (Bortle Class 2) that it becomes “easily seen with naked eye”, and in excellent dark sky sites (Bortle Class 1) it is a “direct vision naked-eye object”. It is located near the Andromeda Galaxy, in the opposite direction from Mirach.
5. Orion Nebula, M42
The Orion Nebula is one of the brighter nebulae in the sky, and therefore is seen relatively easily. It lies in the middle of Orion’s sword. Under suburban skies it will be visible to the naked eye, but take binoculars out under rural skies (Bortle class 4 or better) and you’ll be treated to a stunning view of this beautiful object. The Orion Nebula is a region of star birth, located only 1300 light years away.
Coming in part two! Meteor Showers, Northern Lights, Zodiacal Light, Gegenschein, and The Green Flash.
Have you been lucky enough to see any of these objects under a dark sky? What would be one your dark sky bucket list?