Star Trails: what to do when there are no northern lights

Sometimes, we find ourselves in the right location, perfect sky, a thermos full of coffee and a ton of patience. But that is not enough: we need a northern light, dancing above us.
The question is: what to do if the queen of the night does not appear?

We can of course drive back home and be sad. Another option is to wait longer: maybe it will come later, stronger than ever. But instead of speculating, or being completely frustrated, why not try new experiments? Since it is during night time, you will not be able to chase animals, or get awesome landscapes with the sunrise. Still, we have to make the best out of every situation.

Look at your surrounding: what do you see in the middle of the night? Stars. Lots of them. And we all know that stars move above us, we just cannot see it with our naked eye. Our cameras, on the other hand, can see them. With a long enough exposure time, we will be able to see star trails. It should be enough to have one minute exposure time, and you will already see that the stars are not just dots, but small lines.
What happens if you capture 30 minutes? 3 hours? There are several issues that need to be taken into account: you want to have a dark sky, so you have to use filters, or do it in the computer: applying the proper commands in Photoshop, and with patience, you can get star trails from single shots.

One of the easiest approaches for the star trail photographing (if you plan to use your computer afterwards), is to use the same technique as the time-lapse photography explained in my previous posts.

The next picture, for example, is a stack of 50 minutes:

The big light to the left is the moon. See how much do stars move in less than an hour!

I also mounted this sequence as a video where the stars leave a trail behind them. Please note that the video has been prepared with 30fps, with 30 seconds exposure time for each frame:

There is one main issue I did not take into account for this video: I did not include the polar star, which would give a static point in the video. Think twice, shot once...