Reflection Rainbows

Stephen Duffield was on his way across to Vallay Island, North Uist in the Outer Hebrides of Scotland on the morning of 22nd December '18 when he saw this unusual group of four rainbows ( the fourth at far left is faint and diffuse).

Two are 'normal' primary and secondary bows separated by the dark sky of Alexander's dark band. The others, curving outwards from them, are reflection rainbows produced by a second 'sun' shining upwards from smooth water.

Image ©Stephen Duffield, shown with permission

Ordinary primary and secondary rainbows are always centred on a point below the horizon and directly opposite the sun.

When sunlight reflects from a lake or smooth sea, rainbow forming raindrops 'see' two suns. One is in the sky, the second is the same distance below the horizon. Both suns form their own primary and secondary bows.

It gets more complicated!