Pollen corona (w-846-13)
In gallery: Photos of the month (2007)
Related photos: Atmospheric optics
A magnificent pollen corona appeared around the sun for about a week during March, over New Mexico (USA). Pollen from trees are abundant in the lower atmosphere at this time of year, if there is no rain and no strong wind. Pollen can cause coronas around the sun and moon much like water droplets in clouds do, but pollen are so very similar in size to one another that the corona can be spectacular, as the one in this photo. As many as three diffraction rings can be seen, in addition to the central aureole. This aureole is overexposed in the photo due to the large difference in brightness. The pollen float in the lower atmosphere and the corona could also be seen in front of the mountaintop (Socorro Peak), before the sun disappeared behind the summit. After the sun was blocked by the mountain, the central aureole acted as a second light source to form an elongated, faint aureole in the pollen floating in front of the mountaintop.
I positioned myself in a part of the town of Socorro where the sun would barely be eclipsed by the top of Socorro Peak. The corona was slightly elongated in a vertical direction, but this is not noticeable in this photo. Nikon FE, Fujichrome Provia 100F, 135mm Nikkor lens. The pollen were likely either cedar, juniper or elm. Photographed on March 14th.