Rainbow Catcher
Goal: drop the sun low and slide the rain across the bow to fill the meter.
The fainter outer bow is the double: light bounces twice inside each drop, so its colors run in reverse, red on the inside. The dim strip between the two bows is called Alexander's band.
Why 42 and 51 degrees?
Inside each drop the main bow's light bounces once and leaves near 42 degrees from the point opposite the sun. The double bounces twice, which sends it out near 51 degrees and flips the color order. That extra bounce loses light too, so the double looks fainter and sits higher, just outside the first bow.
A rainbow is not sitting at a fixed spot. Sunlight bends through each raindrop and bounces out at about 42 degrees, forming a ring around the antisolar point, the direction of your own shadow’s head. Drop the sun toward the horizon for a fuller arc, slide the rain so the ring lands on real drops, and turn your head to watch the whole bow swing. Then hit walk and see how close you get. Leave the double rainbow on to spot the fainter second bow, which bounces twice inside each drop and runs its colors backwards.