A couple of days ago, during an early morning walk in the park, Melissa and I noticed a bright white “halo” around the shadows of our heads in the dewy grass. I took this picture:
Later, I looked it up on an excellent website called Atmospheric Optics and found that the phenomenon is called the heiligenschein or “holy light.” We could only see the light around the shadow of our own head and not the other person’s because it only occurs around the antisolar point (the point directly opposite the sun.) Notice there is no light around the lamp post shadow. According to the website the dew droplets act as tiny crude lenses to focus the sunlight on the leaves of grass, most of which is then reflected directly back through the droplets to our eyes. There are no colors involved, as in a rainbow, just backscattering of sunlight. We did see dewbows also in the wet grass several feet out on either side of the heiligenschein but, unfortunately, they were too faint to show up on pictures.
Does dew on plants cause sylvanshine?
Yes. Heiligenschein (holy light) is a general term for any effect which produces a glow around the anti-solar point, including sylvanshine, glories, etc.