The familiar primary and secondary rainbows have been known since there were eyes. The long sought 3rd and 4th order rainbows were finally imaged in 2011. Now we have the 5th order!
Harald Edens’ discovery image was taken on August 8, 2012 from the Langmuir Laboratory for Atmospheric Research near the 10,800-foot summit of South Baldy Peak, New Mexico, USA. This is the first-ever image on which the 5th order rainbow is positively identified. This version is considerably enhanced. The raw camera image is here (link to image).
The 5th order lies between the primary and secondary rainbows in the dark sky of Alexanders dark band, where there is no primary or secondary rainbow light.
The fabled quinary or 5th order rainbow is made by sunlight reflected five times inside raindrops. We see only its broad greens tending to blue towards the primary bow. Its yellows and reds are hidden behind the secondary bow.
Harald has now photographed the 5th order several times. He ascribes his success to the very bright rainbows formed locally from small thunderstorms and to the exceptionally clear high altitude low density air. Astute observation over many years by an atmospheric optics expert also helps somewhat! His scientific account will be published in the Journal of Applied Optics.
- EarthSky
