It is said Tromso, Norway is the best place to see northern lights. We stayed in this amazing place for 5 nights from Feb 16, 2018. This was a once in a lifetime experience we would keep it in our memory forever. Hopefully my information can help you prepare your trip better. Please be aware that the information only came from my short-time visit.
Most good spots to watch northern lights seemed to be on the west side of the islands. I recommend to stay west side outside of the city and rent a car to explore the area. Before we went there I was skeptical if we should join a guided tour as we were not sure if we were able to drive in snow conditions. It turned out driving was the best option for us. The roads were very well maintained. Driving, at least to the places I described below, was a problem at all.
There are two roads I liked the best. The first one was the road to Tromvik. Along the road there were many places you can see northern lights. The very best location, which I did not see many people mentioned, was around a wild camping area, called Gloshaugen Camp, at GPS coordinates 69.745290, 18.353690. It was a mountain scene. This area also provided nice hiking opportunities.
Another road I liked very much was highway 862 to Sommaroya. Again, there are many places you can see the northern lights. I liked the view point at GPS coordinates 69.621424, 18.058710. The area around Kattfjordvatnet (GPS coordinates 69.65061, 18.50677) was also very nice. My suggestion is to drive along those roads at a daytime to see the condition and decided by yourself. You want places with less or no city lights. Ideally the place would have some interesting objects on ground, for example, mountains or water.
The town of Sommaroya was extremely pretty. Although I missed the chance to catch a sunset there, I know it should be an excellent location for that. If I went there again, I would stay a couple nights there.
My GPS locations, Tromso Northern Lights.gpx, can be downloaded from GPS Tracks Collection.
Keep in mind that this is only for your reference as there are many other good spots I did not have a chance to mark. You need to explore them by yourself.
For gears to take northern lights photos, I mainly used Sony A7R III camera with a Sigma MC-11 adapter. The lens I used most was Sigma 14mm F1.8 ART that I bought particularly for this trip. It turned out this lens was amazing and I highly recommend it for northern lights. I also used Canon 16-35 F2.8 III. Because northern light shapes change quickly, in general you want to keep exposure time shorter, usually between 8 to 15 seconds, which requires higher ISO settings. The Sigma lens can effectively reduce ISO from 3200 to 1600, which showed a big difference on noise level. I also recommend to bring Microspikes if you have.
I recommend to stay multiple nights to increase the chance to see the magic. There was one night with clear sky - absolutely no cloud, we did not see northern lights. I would imagine if people only stay there for that night they would be disappointed. If you do some research, you might notice KP Index. From talking to a guide, what I learned was the KP Index did not really mean much at Tromso. KP Index is a value indicates from how far people can see northern light. Because Tromso is so close to the north pole, even the KP Index is less than 1, people still can see it. A very important concept is KP Index does NOT indicate the strength of solar activities, which is the key to see good northern lights. There is also no reliable way to predict the strength of solar activities. My experience also proved the guide was right as the night we did not see northern light, KP Index was actually around 2 or 3. For us, as long as sky is clear we just go out to test our luck.
Northern Lights on the road Fv57 (GPS 69.740401, 18.496424)
Northern Lights on the road Fv57 (GPS 69.740401, 18.496424)
Panoramic view of Tromso night scape | The photo was taken at top of cable car station, Fjellheisen.
Northern Lights at Sommaroya
Sunset at Tromso
Snow mountain reflected on lake on the way to Sommaroya
Houses in snow
Sunset on the way to Sommaroya
Northern Lights at Kattfjordvatnet
Northern Lights at Gloshaugen Camp
Northern Lights at Gloshaugen Camp
Northern Lights at Gloshaugen Camp
Northern Lights at Gloshaugen Camp
Northern Lights at Gloshaugen Camp