3rd and 4th order rainbows – technical details
The lens has a distortion, but nevertheless I tried to compare the width of the first, second and third order rainbows. I selected three fragments, each of them at an approximately identical distance from the center of the photo to get an identical distortion.
The first order rainbow has supernumeraries.
The second order rainbow seems to be wider than that of the first order.
The width of the third order rainbow appears the same as or greater than that of the second order rainbow. The digital colour noise didn´t allow an exact comparison.
I tried to calculate the width of the rainbow, it seems to be between 1 and 5 degrees, but I think it is probably 2 or 3 degrees (graphic 1 and 2).
I estimate the radius of the third order rainbow at about 39 to 43 degrees, with the blue colour at 39 and the red colour at 43 degrees. It seems to me that the brightest part of the rainbow had a radius of 41 degrees, but it also was very faint. I don´t know which colour corresponds to this radius, I think it is green or perhaps yellow. It is difficult to see because of the colour noise.
Author: Sergei Antipov, Russia