Spectral index map of 1ES 1959+650 between 15 and 22 GHz, on 2003 October 31. Contours are drawn from spectral indices of −1.5 to 0.5 in steps of 0.25. Spectral index is calculated as ﹩S\propto \nu ^{\alpha }﹩, where S is the flux density, ν is the observing frequency, and α is the spectral index. The spectral index has been plotted at all points where the flux density is at least 4 times the flux density of the lowest contour on the images at both frequencies, i.e., at least three contours up on both relevant images.