–part 11 of the essay An astronomer in Texas–

Several days later, the weather got worse again. During the day, we got treated by a beautiful, sky-spanning rainbow. Infrared is a very useful tool to improve the detail of such an event since it shows a smaller wavelength range. Here, one can see the secondary rainbow, Alexander’s dark band to the right of the primary rainbow, and supernumaries (more on that in the following picture).