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Imagine a three thousand-mile astronomy voyage “hunting the light”. Usually, astronomers avoid the light, but not when it's the aurora borealis, the famed northern lights. Here is the first of two articles about the Norwegian ships that carry cargo and people between the towns of the Arctic Circle.

Hurtigruten - Hunting the Light

I wrote this article three years ago, but the aurora season is again in full flow in the Arctic Circle. And I'm off on an astronomy voyage hoping to see the lights again.

Very cool Mona

The K index is a measure of the sort of auroral activity. Away from city lights a 4 should produce some northern lights. But although activity around Norway was good, the weather where we were wasn't. Mild, but completely cloudy.

Today has been blue-skied and sunny. The leaves have started to show autumn and the effect should be strong as we go north. Alas, what was causing all the brilliant aurorae of earlier in the week is disappearing. Yet aurorae are expected tonight, so if it stays clear we could be lucky even though we're still not in the Arctic circle.

Click here to find out more about Aurorae – Polar Light Shows.

Friday we sailed out of Bergen. Cloudy skies, but not actually raining. Bergen is known for its connection with the composer Grieg and for its rain - it rains an average of 202 per year!

But yesterday it was sunny as we sailed Ålesund (known for its art deco buildings) and took a trip up the lovely Hjørundfjord to the little village of Urke. Splendid trip with mountains rising off the fjord, autumn color and blue skies.

Yesterday evening the sky stayed clear and there was star-gazing on deck. Wow! I hadn't seen such a sky since a March trip to Norway. (My most recent trip was during the summer. No stars!) We could see the Milky Way, not something many people in Britain can see. And as well as constellations, several satellites and a "shooting star". The only thing missing was any hint of northern lights. Admittedly, we were still fairly far to the south, but in March we actually saw some auroral activity after leaving Bergen.

Sunday night there was some auroral activity. It lasted a long time, but it wasn't very active. In fact, it was rather like staring at clouds - unless you took a picture. The color receptors in our eyes aren't activated by weak light, so the aurorae may just look grey. The camera however has no trouble with this and you can actually see the green color - which tends to predominate - in an aurora.

Last night it was completely overcast and sometimes raining, so there was nothing else to see in the sky. However the ship went into the Trollfjord - short, narrow, dead-ended fjord - using its spotlight to pick out scenic highlights. The ships don't always go into the Trollfjord, it depends on the weather. The opening is narrow, so they keep away in windy weather. And they don't go right inside in the winter when there's ice and snow. A ship would be in danger from avalanches.

Here is Hurtigruten ship MS Trollfjord.

For the occasion they also serve a fish soup up on the top deck and trolls are seen on board. (They have a suspicious resemblance to members of the crew.)

In Tromsø in the far north of Norway the astronomy group on board the ship Midnatsol went to visit the Nordnorsk Vitensenter (Northern Norway Science Center). We saw a presentation about the constellations of the Vikings and those of the Sami people. You can find out more about it in Northern Lights Planetarium.

There have been northern (and southern!) lights around, but ours have been hidden behind clouds and lost in the rain. But last night there was a splendid display which filled the sky and lasted for several hours.

People tend to think auroral activity is related to sunspots, but this doesn't seem to be the case. There are no really active sunspots at the moment. But there is a coronal hole, a place where particles from the Sun are rushing out to form a "high-speed solar wind stream". Here is a picture taken by NASA's Solar Dynamics Observatory .

When the stream hit Earth the resulting geomagnetic storm caused aurorae on Earth, including those last night seen by the astronomy group on board Midnatsol in the fjords of Norway.

We've been through a whole range of weather in the last day and a half - some snow, plenty of rain, some sunshine (and a rainbow!), strong winds and some rocking and rolling in rather lively seas, and are now back to calm seas. And it was preceded by a night of superb northern lights that filled the sky for hours.

Hurtigruten - Seeing the Light is an account of the astronomy highlights of a 2012 voyage. (Unfortunately, you won't be able to see the images unless you're a member of Pinterest - or, I guess, willing to join.)

Late yesterday afternoon we went into the Trollfjord again. This is the only voyage I've been on in which we've gone twice into the Trollfjord, northbound and southbound. (It's more usual that the weather conditions have stopped the ship going in at all!) The sky was grey, and partly surrounding the Trollfjord are taller mountains that loom in the background. Their tops had a sprinkling of fresh snow. The sparse vegetation was in its autumn colors and recent rain had created a number of waterfalls.

But we realized that we weren't alone. There were two RIBs (zodiacs) full of people also coming in. But more interestingly, sea eagles! RIB safaris often have fish for them, but I fear the birds were disappointed yesterday. No snacks.

There were three of the sea eagles (plus a few gulls) altogether. It takes a while to spot them in the fjord and keep them in view. In the dim light their dark coloration blended with the rocks behind them, especially since we were getting a side view. They glide and soar and swoop, majestic and graceful. We were all quite entranced.

Too cloudy for stargazing last night, but watching the sea eagles was a wonderful experience.

Vardø was one of our stops within the Arctic Circle, and it has an astronomy connection. The old town hall was built on the site of the observatory Father Hell built for watching the 1769 Transit of Venus. (The new complex replacing the town hall has a swimming pool, library and various features.)

Maximilian Hell was the director of the Vienna Observatory and a highly respected astronomical observer. The King of Denmark invited him to observe the transit in northern Norway. (Norway was part of Denmark at the time.) The king would sponsor the expedition.

It was hard work building the observatory and preparing for the June transit during the Arctic winter. But it was a good observing site because the Sun doesn't set in Vardø in June, so Hell was able to observe the entire transit. (He was also fortunate with the weather.)

There were commemorative plaques on the old building, but they've been removed for storage. We hope they'll have a place for them when the building work is completed. Vardø, by the way, also had a good view of the 2012 Transit of Venus.