Are you ready for '17 NLC season?

If you live between 45 and 65 degrees of latitude, your bright summer nights are not as boring as you might think. Have you heard of noctilucent clouds? Here is what they are and how to experience them in 2017!

As the Earth continues its path on its elliptical orbit around the sun, high latitudes and higher mid-latitudes of the northern hemisphere are entering the midnight sun season. If you go too far up north, the sun never sets, but at lower latitude, like southern Scandinavia, the sun goes down just a few degrees under the horizon and lingers there for a few hours, gliding unnoticed from the north-west to the north-east. This allows summer nights to remain in a constant twilight and it never gets dark enough to see the milky way or auroras for example.

However this situation, combined with some precise conditions, can give birth to one of the most intriguing and jaw-dropping shows on Earth: noctilucent clouds. While the Earth rotates far away from the sun in the summer, its mesosphere gets cooler, allowing the formation of tiny ice particles. These particle form the highest clouds on our planet (82km in the atmosphere) and wouldn't be visible if it wasn't for the bright nights!

Credits: NASA

See, the sun being from 0 to 6 degrees under the horizon can, with the help of tropospheric clouds, emit rays that illuminate this ice layer, making the viewer's night sky glow electric blue, yellow and orange! The Noctilucent cloud (NLC) season roughly starts at the end of May and finishes at the end of July in Denmark. You can gaze upon them when the weather is clear and potentially all night, most likely towards the north as the Sun follows its course under the horizon, back-lighting the ice sheet.

As the 2017 NLC chasing season is about to kick off in Denmark, I assembled some of the best shots of the 2016 season in a 4K time-lapse video as a tribute, and also teaser for the 2017 season, in hope to encourage more and more people to go out and experience these mind-boggling displays.


Tips on how to spot and photograph NLC:

NLCs can be spotted all the way down to 45 degrees North (some have been spotted in France, Germany, the UK...!). As you go farther up north, the nights get brighter and brighter, decreasing your chances and time-window to see them. The perfect latitude is between 48 and 55 degrees North, where you have about four hours of twilight darkness (mostly nautical and civil twilight) during the shortest nights of May through July. The best locations are Ireland, mid-UK, Southern Scandinavia (+ Estonia, Latvia...), mid-Russia, mid-Canada. You will know when you see NLCs. They are really bright filament-like structures developing towards the north. Your best chances are between 11:00pm and 2-3:00 am on a clear night.

NLCs are not the most difficult subject in the world to photograph, whereas time-lapsing them is a tiny bit more challenging due to their more or less fast-moving aspect. The most challenging is probably the fact that they constitute a very bright patch on a merely dark frame, making your histogram go crazy. You have to be careful not to blow your highlights while keeping the nice contrast of the scene. You can also try using a graduated ND filter (never tried but it can work!) if you are too afraid of the brightness. Speaking of which, you have to assess on the go: if NLCs are not too bright, like on the picture above, then you can definitely use your usual twilight setting presets. If they are very bright, I would recommend that you downgrade your exposure time one or two stops. It is generally easier to correct brightness in post-processing than on the field if you do not have a good live view. The picture above is taken with Sony a7rII and Sony FE 28mm f/2 @ ISO 400, 2'', f/2.8. I generally do not go over ISO 640/800, depending on the brightness and the time of night. If you are shooting stills, set you aperture higher than minimal native f/stop to gain sharpness, set your ISO to 400-500 (to avoid noise) and open your shutter accordingly! You should be good to go! Sometimes NLCs cover the whole night sky. This happens when the sun is in civil twilight zone (right after sunset or just before sunup)! I am really hoping you can experience it like I did last year. Here is a real-time footage from last year in Denmark (some of it is taken with my iPhone 6 to show you how bright they can actually be!).

Get ready for a promising 2017 NLC season!!