Ya know, I don’t know. I assumed chromatic aberration, myself, but I don’t know. If it’s not, then it’s a good thing I didn’t correct it. It was taken on a somewhat pricy piece of quality glass (about $1200), but such extreme contrast and the magenta color suggests chromatic aberration to me. But I don’t know for certain.
The magenta color occurred in the exact same spot with three different cameras/lenses in our group, so I don’t think it’s chromatic aberration.
Excellent points by SCSimmons and scr4. Here’s one more factor.
Humans have excellent “digital zoom”. Our eye has no actual optical zoom capability. But our brain effortlessly focusses in on one or another part of the visual scene, giving us in effect the ability to “zoom in” on one or another part of a visual scene while “cropping out” or ignoring or de-emphasizing the rest.
We can also jump from point to point from moment to moment in a mostly static scene. Which has the effect of creating a “movie” of zoomed-in tiles which is much larger and more vivid than an equivalent still pic taken by a camera of equivalent focal length to the eye itself.
Whatever it is, it’s an artifact of the camera. There is no emission from that part of the Moon.
Was it taken with the camera on a fixed tripod? It may have something to do with the motion of the Sun across the sky, because the fringing is in the east/west direction. Though I’m not sure why a motion blur would have a magenta tint.