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Last summer, I snuck out with a row boat around 4am. Eventually with the sun risen but still quite low in the horizon, I was rowing in the middle of the absolutely still lake when I witnessed an optical phenomenon unlike anything that I've ever seen before: I found myself enclosed in a triangle in which, the sun was in one corner, and in the other corners, the surface of the lake had turned rainbow-colored.

As a photographer I technically understand what happens there, i.e. even though it looked clear to the eye, there obviously must've been some nocturnal mist left on the water surface to act as a medium, and, had there been more moisture particles higher up in the air, I should've seen an entire rainbow connecting these two reflections. But due to the conditions, apparently all I saw was the ends of the rainbow, on their own.

I tried to search for instances or info on this, but found none. Does this specific phenomenon have a name? Under what conditions might one expect to possibly witness this phenomenon?

Here's a quick illustration of the setting, as perceived subjectively. I made a quick simulation of the sun in that time and location using Stellarium , and the sun was about 11° above the horizon (actual bald horizon, not including trees, hills etc.)

setting

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  • $\begingroup$ Where was the sun relative to you and the image you saw when you saw it (e.g. directly behind you, in front of you)? $\endgroup$
    – casey
    Nov 24, 2015 at 16:11
  • $\begingroup$ @casey I actually just described it there: I was in the middle of a lake, while the sun, and the two identical colorful reflections on the water's surface appeared to enclose me into an approximate triangle. $\endgroup$
    – user158589
    Nov 24, 2015 at 19:58
  • $\begingroup$ I understand that much, but it isn't clear to me from that how you are oriented. I could assume you were looking at the sunrise, but I'd rather hear that specifically than assume it because solar orientation plays a role on possible optical phenomena. $\endgroup$
    – casey
    Nov 24, 2015 at 20:01
  • $\begingroup$ @casey I'm in the middle of the lake, and when the elements form a triangle around me, each instance is too far from another for me to be able to see, for example, the sun as well as a reflection at the same time. One or the other will always be behind me. The location is exactly like it would be for a normal rainbow. $\endgroup$
    – user158589
    Nov 24, 2015 at 21:35
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    $\begingroup$ @user158589 As casey asked before, please mention whether the sun was behind you or infront of you.. (or on left/right side) $\endgroup$
    – Mr_Green
    Nov 25, 2015 at 4:51

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It appears from your picture that there is some mist above the lake surface. The phenomenon will be due to the same mechanism that causes conventional rainbows. The angles between the sun, the mist/cloud, and the observer will be identical but you will only see this with the sun low in the sky since the mist is near the water. That will also make the rainbow appear to be floating on the water surface (great photo, btw). I think the dark background of the trees helps make the colours more intense. The low sun means that the spectrum can be seen on either side and behind the observer. So you are correct that it will form a triangle around you. If I'm visualizing things properly, in your photo the sun would be to your right - on the violet side of the rainbow.

I am not aware of any distinct name for this, possibly because it is not really different from a rainbow from a scientific perspective or because too few scientists are awake at 4 AM.

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  • $\begingroup$ Yes, there must have been mist left even though it looks like there isn't. Just before the sun rose, the rising mist was still boldly visible and started to fade when the sun started warming the air. But contrary to what you're guessing, take a look at the shadows: Seeing this view, the sun was in the left, red side. I regret that I didn't shoot a 360° video pan, because now I'm feeling slightly uncertain of whether there were 2 or 3 reflections; The lake was of a very complex, elongated shape, it continued to the horizon and there were islands. Moving across the lake, it's very difficult for $\endgroup$
    – user158589
    Nov 26, 2015 at 10:47
  • $\begingroup$ the observer to comprehend one's own location while in there. I created a quick illustration, please see the original post. The photo that you see was taken of the reflection which in the illustration is "at 12:30". $\endgroup$
    – user158589
    Nov 26, 2015 at 11:05

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