Newton's Rings

Last night the girlfriend and I went out to do some more astrophotography.  We drove out to The Glenbow Ranch to see what we could find.  To our amazement we managed to capture The Alberta Northern Lights!  Since it was a clear cold night it created perfect conditions to photograph the aurorae!  

We used a 500 lumen flashlight to light paint some of the environment in.  I also purchased a handy head light lamp to help navigate the darkness.  I used a Canon EF 40mm f/2.8 STM Lens and a Canon EF 24-105mm f/4L IS USM Lens.  The 40mm was a bit tight but I really enjoyed working with the 2.8 aperture in the low light.  

 

While editing in post I found this weird circle pattern in some of my photos.   At first I thought something was wrong with my 5D's sensor but it turned out to be Newton's Rings.   It was an interesting encounter and I will have to read up on how to avoid it next time. 

Newton’s rings is a phenomenon in which an interference pattern is created by the reflection of light between two surfaces—a spherical surface and an adjacent flat surface. It is named after Isaac Newton, who first studied them in 1717.
— Wikipedia