Bubble chart plots of low-order Zernike aberration coefficients in full-pyramid representation (a) and in half-pyramid representation (b). The area of the depicted aberration terms (bubble size) is proportional to the magnitude of its RMS-normalized Zernike coefficient $c_n^m$. The blue circles on the upper right represent the areas of the total RMS-deviation of the wavefront error (dark blue) and its fitted RMS-deviation by the shown low-order aberrations fit of a 10th order polynomial (light blue). The numbers within the pyramid represent the RMS-normalized Zernike coefficients [nm], whereas the numbers in the blue reference circles (upper right corner) are the RMS-values [nm] of the original wavefront and its fitted 10th-order counterpart. Primary coma and trefoil are the main aberration terms.