Thread by @paulhaworth

From late May through July, one of the most dynamic and beautiful spectacles can be seen in the night sky from mid latitudes. The shimmering iridescence of Noctilucent Clouds (NLCs) is worth getting out to watch and they're easy to photograph.

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#noctilucentclouds #NLCNow

Derived from the Latin for "night-shining", noctilucent clouds usually resemble luminous, silvery cirrus clouds (the wispy ones) and start to appear in the north west to north shortly after sunset as the sky begins to get dark enough to see the brighter stars. 2/25

As dusk deepens, NLCs appear to get brighter and cover a larger part of the sky - it's not uncommon for them to stretch overhead during a strong display. Displays can last from a few minutes to hours and even all night. 3/25

Through binoculars NLCs reveal beautiful fine details, corrugations and tendrils and you'll notice they roll and shimmer like waves on an ocean. Timelapse photography captures this motion particularly well but even by eye you'll notice their movement over time. 4/25

NLCs form 70-90km up in the atmosphere, around 9 times higher than the typical cruising altitude of a jumbo jet and 10 times higher than Everest, in a layer called the mesosphere. Ice crystals condense around atmospheric dust, which reflect sunlight from below the horizon. 5/25

Traditionally considered rare, NLCs are thought to be becoming more frequent due to an increase in greenhouse gases, specifically methane, which reacts with atmospheric oxidants producing water vapour. Burned up meteors contribute the dust around which the ice crystals form. 6/25

Anecdotally, in my 30+ year amateur astronomy career, NLCs are considerably more common now then they were when I was younger. I only remember one definite sighting from back then in 1995, which I tried to capture (badly!) on my dad's film SLR. 7/25

It can be easy initially to confuse NLCs for normal tropospheric clouds. The rule of thumb is if the clouds are darker than the background sky, they're tropospheric clouds (which can still be stunning!). If they appear to shine relative to the background, they're NLCs. 8/25

Predicting which nights NLCs will appear is tricky - a combination of art, science and luck. But you've got to be in it to win it - so get out to take a look. The only thing that genuinely scuppers you is complete (normal) cloud cover. Here's a tip. 9/25

One indicator of NLC activity is reflections from VHF radar from the typical altitudes at which NLCs form. Don't have your own research radar? The Liebniz Institute of Atmospheric Physics has you covered and makes data from their Kuehlungsborn radar available on the web. 10/25

On the radar feed you can see altitude on the Y axis, time on the X axis, and the intensity of the red blobs relates to the "strength" of the radar reflections. Strong clusters of reflections can indicate an increased likelihood of NLCs that evening. 11/25 iap-kborn.de/OSWIN-VHF-Rada…

One of the joys of NLCs is how easy they are to photograph. Even a phone camera can take pleasing pictures if you hold it still enough while it exposes to compensate for the low light levels. This phone shot shows my brother taking his first ever NLC photo. 12/25

They even show up on phone videos - this clip shows me getting rather excited as a very bright display started kicking off last year - I wanted to tell anyone I knew to get outside right now and see the show! You could try a phone timelapse over half an hour or so. 13/25

A DSLR or mirrorless camera will get you spectacular results. Ideally you'd use a tripod so you can expose for a few seconds without the image becoming blurred due to your hands shaking. But you could rest the camera on a wall or post (or propped on the ground) too. 14/25

Here's how to shoot NLCs with a DSLR. Don't be afraid to experiment, and if it all becomes too stressful in the moment, just pack the camera away and enjoy the show. Initially you'd want a reasonably wide lens - anything from 14mm to 50mm would be a good start. 15/25

It's worth finding a nice foreground. You'll find that structures, trees etc can produce nice silhouettes against the gentle twilight sky. Still lakes or ponds can reflect the NLC glow really nicely as well. This stunning image is from @OldDairyLowRow

https://twitter.com/OldDairyLowRow/status/1403986280778768384?s=20&t=eq_0Q8Dt8O3gVjoJYNqK6w

The best images are well composed with interesting foregrounds. It's worth scouting those out during the daytime. Ideally you need something tall (so it stands out against the NLCs) but with a clear horizon around it when viewed from the south looking north. 17/25

Settings will depend on the camera, level of twilight, any moon and your location. As a starting point, I'd recommend opening your aperture quite wide (say, but f/2.8 to f/5), ISO400 and exposure of between 1.5s and 4s. Play with exposures until it looks good. 18/25

But first let's focus. Switch your camera to LiveView and point it at something far away - a tree, star, moon or the horizon. Zoom in on LiveView. Turn your focus ring until the object is as sharp as possible. This will get you crisp focus and lots of detail in the NLCs. 19/25

The you're ready to roll. If you shoot in RAW (you should), your image will respond really nicely to some processing in a tool like Lightroom.Playing with the highlights/whites/shadows/clarity/contrast sliders in particular work well. Don't overdo the saturation, like this! 20/25

The next level comes from timelapse - a sequence of photos stitched together into a video. Timelapse compresses time so you can see the magical motion of the NLCs sped up. A timelapse is remarkably easy to do and there are free tools online to help. 21/25

When timelapsing NLCs, I recommend using an interval between shots of no more than 5 or 6 seconds (though it may depend on how long your exposure is). This will give you a nice long sequence that should show movement at a pleasing pace. But experiment! 22/25

If your camera doesn't have a built in intervalometer, they're on Amazon for less than £20. Be sure to get the right connection for your camera. And make sure your memory card has plenty of space - timelapses can be storage-hungry! 23/25

The best thing about timelapsing NLCs is that it gives you a chance to sit back and enjoy the show. My advice is to take a chair and a cold beer to your location. It's an incredibly relaxing way to spend an evening, especially if there's a comet in the sky! 24/25

If you head to out to see NLCs or shoot them, good luck and let me know how you get on. I'd love to see your pics so do tag me in them. There's loads of expertise here on Twitter to help you. Clear skies! ✨📷😊 25/25

Here’s that radar link again. Above is dud. iap-kborn.de/forschung/abte…