On April 8, 2016 a nice circum-horizon arc appeared. I had seen a similar arc a month earlier, but only had my cell phone to photograph it. I tried a photograph with my phone but couldn't see the arc in the picture, so I took off my glasses to get a closer look at the image. I was wearing a set of polarized clip-on sunglasses over my corrective lenses and realized that when removed, I couldn't see the arc in the sky either. I put the sunglasses back on, and there was the arc again. Next, I tried photographing the arc through my sunglasses. The polarized photos were noticeably better at capturing the perceived color. So when I saw a much brighter arc, one that was visible without polarized sunglasses, I took photos with my Canon digital rebel camera with and without my sunglasses over the lens.
Circum-horizon arc with polarizing sunglasses over the lens
Circum-horizon arc using the camera's kit lens as is.
A more professional photographer would probably buy polarizing filters for all his lenses.
I use this blog as a companion to my website www.brightstarstemeculavalley.org, where I call attention to local light pollution and share my enthusiasm for science and astronomy. I'm also a contributor to www.SkepticalScience.com.