Fogbows
All photos taken by and (c) Bruce G. Marcot.
Here we see a "fogbow" -- a colorless rainbow -- in the crater of Haleakala Volcano on the island of Maui in the state of Hawai'i.
A fogbow
forms in the same way as does its multi-hued rainbow cousin, except with fogbows
the water droplets -- here in the
low fog in the crater below -- are far smaller and diffract the light coming
through them far more than with the larger water drops
of rainbows.
What we end up seeing, then, is only white light not split into its component color wavelengths.
Fogbows sometimes have a slight reddish hue on the outside edge and bluish on the inside edge, as also seen in the above photo.
Like rainbows, fogbows occur at the "antisolar" point, that is, with the sun directly behind you as you view them.
And yes, on the left
side of the photo are the astronomical observatory domes of the Institute for
Astronomy.