ph . Astronomy . Galleries . Atmospheric phenomena . Rainbow

A rainbow is an arc of light of many colours that is sometimes seen when the Sun shines on rain. The above photo was taken on 2007 April 12 with the bow appearing low between the hills of Pilgrim's Rest.

Often two bows can be seen, parallel to one another. Shown above is the primary bow; secondary bows are always broader and much less bright, and are not always visible. A double-rainbow can be enjoyed here.

Rainbow hunting tips: (1) check that the Sun is shining as it is raining; (2) the rain must be directly illuminated by sunlight; and (3) stand directly between the Sun and rain with your back to the Sun and look up at the sky in the direction of your shadow. For even better odds of seeing a rainbow, (4) try to be within a few hundred metres of the rain; (5) hope the rain extends over a portion of the sky large enough to accommodate the rainbow arc (angular size is always 42°); and (6) relocate the Sun so it is near the horizon; a rainbow can't form if the Sun is more than 42° above the horizon.

Keep in mind that we each see our own rainbows, and that it will follow you around, like your shadow. Great stuff.

Keywords: Astronomy, astrophotography, atmospheric phenomena, sunset, sunrise