Elusive tertiary and quaternary rainbows captured, on camera
Click the image for enlargement showing the third and fourth (just barely visible) rainbows close to the sun.
We’ve all seen primary rainbows. Some may have seen the secondary rainbow, which is usually a fainter arc a little ways outside the primary.
Turns out there can be two more rainbows, but not near the first two. To find them, you have to turn your head about 40 degrees toward the direction the sunlight is coming from. But don’t expect to see them. According to Loren Grush at Foxnews.com (yes, Fox, but this ain’t politics), there are only five recorded reports of tertiary rainbows in the last 250 years. Quadruple, or quaternary, rainbows are even more rare, but a German storm chaser has captured an image of it, above. Yes, it’s hard to see the fourth bow here, but if you click on the image, you should get a blow-up in which it is more obvious. The first two rainbows are out of the picture. (Yes, we believe they were there.)
Sightings may become more common because meteorologists have just recently developed a technique, which anyone can use, to find the extra spectra. Grush explains the method in her story.
Attention to the phenomenon has been generated by a new report in the journal Applied Optics, which explains that the third and fourth rainbows show up only in just the right combination of lighting conditions and rain droplet sizes. And, as one might expect, the photographed image must be digitally enhanced to bring up the colors.
Perhaps the best account is Alan Boyle‘s at MSNBC.com, which has nice, big versions of the images. Boyle also has more on the photographic details, which figures since his story appears in the Web site’s Photoblog department.
Other stories:
Jason Palmer at BBC News, who is more up-front about the digital enhancement.
Jeff Hecht has more on the details of the image processing at New Scientist.
Photonics Online, a journal we don’t often check, has a good account, unbylined.
-Boyce Rensberger
October 9th, 2011 at 6:21 am
How is the fourth one created? Is it basically just light creating an image of the third one?
October 9th, 2011 at 9:51 am
I recommend that you read the articles to which you will find links in the post. Most of the technical details are there.
October 10th, 2011 at 12:06 pm
Now i a hooked
every time i will see a rainbow i will search for the tertiary and quadruple rainbows…
February 6th, 2012 at 7:16 pm
That’s pretty neat! Oh how I hope that double rainbow guy would make a video on YouTube about tertiary or quaternary rainbows with a follow-up auto-tune version, of course!