Atmospheric
Optics
Changing Rainbows
Aysun �lger imaged these 7 rainbows at different times of the day at Izmir, Turkey.
As the sun descends the bow climbs. The topmost view shows the bow top slightly below the distant horizon.
All images ©Aysun �lger, shown with permission
Almost a sunset bow. The bow is already reddening. The sky inside the bow is noticeably brighter. Dark sky, Alexanders dark band, shows between the primary and secondary bows.
Rainbows are always the same size, about 42° in radius.
Their centre is directly opposite the sun.
When the sun is 42° high the top of the bow grazes the horizon. At sunset the bow top is ~42° high in the sky and a full semi-circle of rainbow decorates the sky.
