Raindrop Diffractions

At the north-shore party, a few raindrops got on my lens as I was timelapsing and made this pattern. I cropped and enhanced it. Pretty cool. For those who have been subjected to the likes of Hecht, Serway, Jackson, etc, You can see the classical Airy pattern in the center, but I'm not sure why the main peak is supressed. Probably something to do with shape, focus, etc. The hexagonal shape is from the shape of the aperture with a knife-edge pattern coming off each. There are also two small Airy patterns in the bottom corner of the hexagon. Camera geeks will love this diffraction tutorial for SLRs.