NLC

  

May is well into its stride now and that means it’s soon going to be NLC-hunting season again for sky-watchers!

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MAY 2021 UPDATE

Keep an eye out for NLC displays from now on. NLC activity has begun in late-May some years, so keep checking the sky, and Twitter and Facebook, from now on. Here are some photos I took of NLC displays in 2020 – there were some really good ones, but the Cumbrian weather prevented me from seeing some exceptional ones. Fingers crossed for better luck this year…!

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“NLC” stands for “noctilucent clouds”, which are, as the photo above (taken in July 2012) and their name both suggest, clouds that shine at night. They aren’t water droplet clouds tho; they’re clouds of ice crystals and dust, that form way, way up in the atmosphere, much higher than ‘normal’ clouds. This means that they are illuminated by the Sun’s rays long after we have seen it set – hence “nocti” and “lucent”. 🙂

Most NLC displays are modest affairs, restricted to a few bands or patches of glowing cloud hovering almost reluctantly above the northern horizon. But if you’re lucky enough to catch a major display of NLC this summer, like the one I photographed above, you’ll have to pinch yourself to prove you’re not dreaming, because trust me, that is something wonderful to behold..!

So, how do you see these magnificent things?

The good news is you don’t ‘need’ *anything*. No telescope, no binoculars – nothing. An NLC display is visible to the naked eye. Having said that, a pair of binoculars is great to use on NLC, because they have very fine, very intricate, very beautiful structure – wisps, curls, streamers and billows – that can’t really be seen well with just the naked eye. So, get hold of a pair of binoculars soon (that pair you have stuffed in a corner under the stairs, or in the garage, will do fine) and you’ll be all set. NLC are very photogenic too, and you can photograph bright displays with a hand-held digital camera, but you really need a digital SLR to take good NLC photographs. But the bottom line is this – to see NLC all you need are your eyes, and a clear night.

Right. WHEN can you see them? Well, NLC “season” begins mid-May, i.e. that’s when displays are possible, but usually it’s the start of June when the first displays occur. So, by all means start looking now, on any clear night, but don’t be too surprised or disappointed if you don ‘t see anything until the start of next month.

And when exactly do you start looking? Well, occasionally a big display of NLC will already be in progress immediately after sunset, and looking north as twilight deepens you will be able to see something like this…

…but they’re rare. Usually nothing happens until around 11.30pm, when the first signs of NLC appear just above the nothern horizon. Not big fluffy billows or streams, more like sharp lines, like golden or silvery vapour trails, something like this…

If you see something like that just above the horizon around midnight, it’s a good sign – it means a display of NLC is brewing! It may fade away to nothing, of course, there’s always a chance of that, but it *could* grow larger and brighter, rearing up from behind that horizon like a dragon unfurling its wings. So, if you see something like this above the northern horizon late on any clear night from now on…

…you might be in for a treat!

But how can you be sure if what you’re seeing is a display of NLC? After all, some ‘normal’  clouds are bright too, right? You will be able to tell if what you are seeing are NLC because the “normal” clouds will look dark, like ink blotches, silhouetted against the bright background sky, and the NLC, like this…

 

So, having seen a hint of NLC activity low in the north, what next? Simple: you wait. Unless it’s feeling particularly evil, and retreats back beyond the horizon, or just drifts apart, as the sky above and around you grows darker and darker, the NLC will grow brighter and brighter, and shine with a beautiful mother-of-pearl luminescence that is totally unlike anything else visible in the sky, ever…

During a major display, as the winds in the upper atmosphere catch the clouds, they form beautiful shapes – ghostly streamers, curls and tendrils of silvery-blue light, like some kind of “phantom” or “energy field” special effect from a science fiction film. Many NLC show a distinctive cross-hatch pattern, and through binoculars you will be able to watch the insides and edges of the clouds changing shape almost by the minute, sculpted by the silent winds blowing high, high above the Earth…

If you’re really lucky you’ll witness an NLC display that covers half the sky or more, and then trust me, you’ll just stand there, shaking your head in disbelief, as the heavens are painted a dozen different shifting shades of electric blue and silver by Nature…

If that happens, you absolutely must try taking some photographs. Don’t worry about settings too much, just set your camera on Auto and click away, you’re bound to get something. But if you can control aperture and exposure etc, try long exposures of several seconds to ensure you record the NLC in all their glory. You’ll need to have your camera on a tripod, and be using a standard 50mm lens or a wide angle lens to take your photographs. If the display is bright, set your camera to 400 ISO and do exposures of just a couple of seconds. If it’s a faint display, try longer exposures. If it’s a particularly vivid display, with a lotof detail and structure, put your best zoom lens on your camera and try some close-ups of individual whirls, curls and whorls.

So, there you go – all you need to know to enjoy this coming NLC season, whenever it starts. I really hope you get to see a display before too long. I saw a couple of lovely displays from here in Kendal last year and have very clear and very fond memories of watching beautiful NLC displays from the playing fields of Cockermouth School and the lay-by at the bottom of The Hay when I was younger, when digital cameras were science fiction and I clicked away with an old Practika SLR, loaded with Boots own “superfast” 400 ASA slide film… Now I have a ‘proper’ DSLR camera, with a brand new kick-ass zoom lens, and I’m all set!

One last thing. Not everyone has the time to go and gaze at the northern sky after dark, just in case there’s something going on, I know. And not everyone has as magnificent a northern skyline as I do when I trek up to Kendal Castle. So how can you improve your chances of seeing the next big NLC display – even better, how can you guarantee not missing it?

This is where the internet comes in.

Back in Ye Olde Days, we had to rely on doing all this manually and personally – i.e. physically checking the northern sky every clear night, and waiting often hours, just in case something happened. Or, if we were lucky, we had a network of fellow NLC fans who would ring around the group, alerting everyone to a display. But now, now we have NLC observing groups, communities, who share alerts and observing repors on Twitter and Facebook, and email, it’s SO much easier!

If you’re reading this, then you’re online… duh… and it means you can access both Twitter and Facebook, and access the alerts and observing reports. Now, I know not everyone is on, or wants to be on Facebook, but really, if you’re serious about wanting to see a display of NLC this year then you need to join in with the NLC action on Twitter. If you’re already a Tweeter, all you have to do is start Following one of the NLC groups on there. Just put #NLC into the search window and you’ll find one (maybe not at the moment, as we’re not ‘in season’ yet, but come June you’ll find something, definitely). If you’re not a Tweeter, then I’m sorry but you need to become one, because if you don’t then there’s a very good chance you could miss the next great NLC display, and then you’d be kicking yourself, wouldn’t you?

Oh, and a word on the most important thing you need to be an NLC watcher: PATIENCE! Patience whilst looking north and scanning the northern sky, waiting for display to start. And patience DURING a display, because, like a display of the northern lights, or a meteor shower, an NLC display can be very active for brief periods, inbetween much quieter periods. And they can fool you: you can watch a display that seems to fade away, and die, and convince yourself “That’s it, it’s over”, only for the NLC to suddenly brighten again and develop even more complicated, even more intricate structure and detail.

So, as Yoda would say: “To watch NLC, patience you must have. Devious, they are. Trick you, they will.”

It comes down to one thing: once you’re out, STAY out, until you’re absolutely sure that the show is over.

…and that’s it! Now you’re ready to drool over the next big NLC display! A quick checklist:

* Plan ahead – select an observing site with a clear, low, northern horizon.

* If you can, start following NLC-related Twitter accounts and Facebook pages, and get yourself on a mailing list or an NLC-watchers forum. Then you’ll have a much better chance of hearing about an NLC display when one starts.

* Get those old binoculars out of the garage!

* Hope for a clear night soon..!

Note : I haven’t really gone very deeply into the science behind NLC here, because there are lots of really detailed and in-depth looks at NLC on the net which can be found with a simple Google search.

I hope you’ve found this introduction to NLC useful. Good luck NLC-hunting during the season ahead!

StuA