People, who love watching auroras need, the higher the Kp, the better. The Kp index measures the disturbances in the Earth’s magnetic field and therefore is a good indicator for the possibility of auroras a.k.a. polar lights. The Kp index ranges from 0 to 9.
When I moved to Skelleftehamn in 2010, I was on the look-out for auroras when the Kp was 3 or higher (and the first winter was extremely dull, when it came to Northern lights). Nowadays I consider looking out when the Kp is 4 or (better) above – or randomly if it’s dark and starry.
Today the Kp was (and still is) really high; between 6 and 7 with a forecast of 7⅔, which is really extraordinary!
When I looked out right after 6 o’clock, I already could see a bright band of Northern light above me. Keep in mind, that this was just 40 minutes after sunset, still in the time of civil twilight and the sky itself was still bright, too.
Ten minutes later I stood at the stony shore of Näsgrundet and took the first photo:
This is probably my favourite shot of today, since the polar lights look so delicate and fragile. I’ve seen such only once before, when the Kp index was as high as today.
Five minutes later: The moon illuminates the Baltic Sea, the island Gåsören is clearly visible at the horizon. The aurora weakened a bit and is not visible in this direction.
16 minutes later, now being 18:40: It became darker and there were enough stars shining to see the constellations. The aurora, that had weakened for some minutes, started to get stronger again.
And I mean stronger! Six other minutes later half of the sky was filled with a huge vortex of polar lights. My wide angle lens (14-24mm) could only catch a part of it.
I switched my place, from the rocky northern shore to the pier for the pilot vessels. Now it’s quite dark and the twilight colours almost had vanished. But now the aurora has weakened to a “nice” one, nothing impressive anymore.
I waited a bit, but nothing extraordinary happens any longer. I head home. Perhaps I’ll be out once more again later …
My nice Gitzo tripod broke some weeks ago. So I’ve been using another one which slows me down. When you take photos of moving motives – yes, polar lights do move – it can be important to know your equipment to be fast. Some shots weren’t made today just because of the unusual (and inferior) tripod.
Have a look at the last photo. Do you see the rainbow coloured arcs on the left side? Nice for you, because I didn’t. At least not directly after taking that photo. Otherwise I would have taken another photo covering the light source on the right side with my hand (making the hand part of the photo). Then I could have merged these two photos into one and got rid of these lens reflections. Well, perhaps next time …