Cloudbow imaged by Kevin Boyle in Northern England, December '08. ©Kevin Boyle, shown with permission.
Atmospheric optics is not all blazes of light and colour. Subtle sky effects are just as interesting and even more satisfying because the hunt is that much more challenging.
Here, a delicate cloudbow is faintly visible against the patchy cloud and blue sky. They are not uncommon but are usually overlooked. Check out damp and cloudy skies by first imagining the rainbow centre directly opposite the sun and then measuring two outstretched hand distances (~40 degrees) from it. That locates the bow position. Find fogbows the same way.
The bow was created by very fine raindrops, hence its comparative lack of colour and much greater width than a rainbow.
Cloudbows can occur when there is no obvious rainfall. They can be created by the cloud droplets themselves or by fine rain - virga - that evaporates before reaching the ground.