My trip to Arizona to shoot the shooting A-10s was a lot of fun and something I have already covered. One aspect of this shoot that caught my interest was the cannon shells in flight. I have seen images from other people that allow you to see the A-10’s shells leaving the muzzle or flying to the target and when I got something similar, I was quite pleased. However, a shot that really caught my eye was one of them that had a background with some clouds visible.
This background provides a mechanism to see any discontinuities in the density of the air as is experienced in a shockwave. This is the effect that is used in Schlieren photography in wind tunnels. The refractive index of the air changes as the density changes. Normally you don’t see this. However, if the background is not continuous, the refraction of the background results in the shockwave being visible. One of the shells showed this up and I thought it was cool. Therefore, I am sharing it here just in case you think it is cool too!