The “diamond ring” phenomenon during a total solar eclipse occurs a few seconds before C2 (2nd contact) and then again a few seconds after C3 (3rd contact). The diamond ring consists of the “diamond” — the sun’s photosphere (either disappearing before C2 or re-emerging after C3), as well as the “ring” — the bright inner corona.
This image was taken just after C3 with a Canon 40D and Canon 100-400 zoom lens @ 400 mm, f/8, 1/60 sec, ISO 100. The totality images were obtained via an automated sequence using Backyard EOS on my PC, but I decided in advance to do the diamond ring manually, since I was worried I might not have access to good GPS data in the Tetons, which would affect the timing of these phenomena. In reality, the GPS was fine, and I missed photographing the diamond ring prior to C2 due to my own stupidity! The solar filter, which had been removed for totality, was replaced within about 5 seconds of taking this image. Minimal processing was done in Adobe Photoshop.