This is a map of error in the reflective surface of the Subaru Telescope's primary mirror, measured in combination with the primary mirror cell. Average error as compared with the ideal reflective surface is just 0.014 microns—about 1/5,000 of the diameter of a human hair. To put it another way, if the primary mirror were the same size as the Big Island of Hawaii, the error would be no more than the thickness of a sheet of paper.