Everyone loves light shows, from fireworks to the Northern Lights, it’s always tremendous. When we were in Grenfell last week, I stayed up to 2AM because the Aurora Borealis were dancing up a storm. That and I wanted to nab a few star trail shots. I couldn’t wait to see what the lcd screen showed me after I finished the 15 minute long exposures. Pure awesome, I thought to myself. That is, until I got the shots home. On the computer monitor I could see something wacky. It looked like a dust spot, but I had just cleaned my camera. Upon closer inspection, I saw these concentric circles radiating out of the center of the image. CRAP! I thought I had destroyed my camera’s sensor chip by taking fireworks shots! 😥
What a gong show! But then, I did some research on the net and came across this article that explains this phenomenon:
With my Nikon lenses I have found that long exposures result in concentric circles showing up in the middle of the images when I use a filter of any kind. Nikon says this is due to the high reflectivity of the aurora. Thanks to the University of Alaska forecaster, the explanation follows. “These are interference fringes due to the parallel faces of the filter and to the narrow spectral emission at 5577 Angstroms in the aurora. That green, atomic oxygen emission line is the strongest emission in the aurora near our film and eye peak sensitivity, so it shows up first when there is any device in the optical path which sorts out the spectral emissions.” So, don’t use filters!
That pretty much sums it up. Lesson learned. If you’re after the Aurora, don’t forget to take your filter off your camera lens! I wish I would have known that before hand. 😳