As we reach the longest day of the year - the summer solstice - daytime is still overpowering the night, and the total time of deep nautical twilight is about two hours tops. It means that from roughly 11:30 pm to 3:00 am, one has plenty of time to linger outside and observe the marvels of the high mid-latitudes, such as the noctilucent clouds.
Two nights before I had had a pretty unpredictable visit. I was sitting on top of Esterhøj in Odsherred, waiting for the clouds to show up. At about 11:30 another man shows up and starts taking pictures! I didn't really pay attention right away, but the photographer suddenly engaged the conversation. We had talked for about 30 minutes when I finally realize, given the information, that the man with the camera is no other than an acquaintance from Scotland I had been talking to on my Facebook page, about photography and aurora! We talked for about 1h30 but decided to drive back home, after realizing that the clouds were not going to show up. I remember saying to him, as we go down the hill, that for some reason the clouds (or the aurora for that matter) occur when you least expect them!
As a matter of fact yesterday when I was out waiting on the very same hill, I started seeing some really faint noctilucent clouds towards the North-East. I have shot them for about an hour and decided to return home as they subsided. It was only 11:30, and the sky was still clear, but I needed some rest, for I was going to the monstrous Roskilde festival the day after... I was certainly far from imagining that if I had stayed up anyway, I would have attended an awesome show...
Some say it is stubbornness, some say it is folly, I say it is perseverance! I decided to stay for something that may not have happened. But against all odds, it paid off. At 1:00 am, the clouds started reappearing, but this time, covering the night sky from the west to the east! I was just filled with excitement.
Even though I have no pretension being an expert in these clouds, I started recognizing a certain pattern. I believe that the different shapes the clouds take is a direct consequence of the thickness of the ice layer and the wind/current speed. When currents are strong, they tend to make ripples. When they are weaker, they makes other shapes like arcs, troughs, bands, knots... It is just like water currents and fluid dynamics! Look at a still river and you will see twirls, whirlpool, little fronts and arcs. Look at a shore and the strong currents shape ripples on the sea floor!
The NLC weren't evolving really fast last night probably because of a weak high altitude current speed. The colors were beautiful and the shapes looked like they had been taken out of a fantasy picture. I am intrigued and maybe a bit sad by the fact that a lot of people don't realize or think these things are unreal, but they do exist! All one needs to do is to step outside after sunset! I know it requires some patience if you are a photographer, but you might encounter this beautiful vista totally accidentally! Here comes a little gallery with the shapes and colors: