So, with my new computer I am finally getting round to sorting out some of the (literally) thousands of digital photos I took on a trip round the world.
I just got to a batch of pictures from the Cook Islands, which reminded me of something I found strange at the time… strange enough to take some photos.
It was sunny, I was just returning from a boat trip on the lagoon, and there was a storm approaching. Cue rainbows as the rain arrived. But here’s the weird thing - whenever I’ve seen double rainbows before, they have been sections of concentric circles.
But this weird formation – pic 1 and pic 2 – caught my eye. I have boosted the contrast and saturation of these pictures just so you can see them easier - hence the addition of some random colour noise in the sky, but you can clearly see that there is an almost vertical rainbow coming off the main arc at a tangent.
Can any meteorological or physics-minded folks explain this? My best guess is that a reflection of the sun in the water is also forming a rainbow, but I can’t really see why it would make that shape…
Well, I think it has to be another source, since a double rainbow has it’s color lineup opposite of the primary rainbow. Your images have the orientation of each rainbow the same.
Mangetout, I think that is just a drop of water on the camera lens - it had started to rain quite hard by that time.
But the double rainbow effect was clear to the naked eye - it had nothing to do with that… in fact it is the only reason I had my camera out in the rain!
I just saw a double rainbow in Prince Edward Island, Canada when visiting 3 weeks ago. I had never seen “one” before… well… two…
Although they were at the same angle…
In the second photo, there’s what appears to be a very faint band of colour running up near the left-hand end of the frame - I believe this is the secondary bow, concentric with the more curved of the two rainbows.
The other one must be from a different light source; possibly something quite nearby, like a shiny tabletop or a window (rainbows that are actually very close (that is to say formed by nearby water droplets) can look as if they are quite distant)
Once I was back on dry land there was a proper, and fairly spectacular, double rainbow to be seen, behaving as it should - concentric and with colours reversed. That’s why I thought it might have been because I was still on the water when I saw the weird one.
Yep, that was my first guess (see OP), but I don’t really see how that would work… hmmm. I don’t think it could have come from the boat I was on at the time (this one )
Anyway, time for me to get some sleep. I will await any words of wisdom from ray-tracing experts overnight…
It could easily happen if the sun was low in the sky behind you.
Imagine this:
sun
#
droplets
`
you <)
_______________________________________________________________________________________
Water
Now imagine what the view to the left from the position of the droplets would be. They’d see the sun, and a reflection of the sun from the water. And then, you’d get a dispersed reflection from both sources from the droplets… i.e., non-concentric multiple rainbows.
Yes, that’s what it is. They’re called reflected-light rainbows. I actually first learned about them from EPOD. I agree with bughunter that you should send these in.
I’d never thought about the possibility of a reflection rainbow, but agree that this could be the case here. The sharp, normal-looking rainbow is an arc of a circle whose center is below the horizon, so you can see it tilted sideways. But if the other is due to a reflection off the sea, its center would be an equal amount above the horizon, so that arc would be more vertical. And the secondary would be less sharp. The data seems to fit.
We’re forever getting double rainbows in Ireland, what with the pissy weather and all.
The second rainbow is supposed to displaced by 33.5 degrees from the primary rainbow… but all the way around. Your pics look like they taper in at the ends - this doesn’t happen with normal double rainbows…
Hey, thanks Achernar. That pic you linked to is almost exactly like what I saw, only their photo came out better. By the time I had got my camera out, the one I saw was already fading.
Mystery solved, and my first guess was right I was thinking about it this morning, and realised that the more vertical angle would make sense for a lower light source, as you would see more of the complete circle.
)
