Zernike Polynomials Used To Describe Wavefront Aberrations

Z0^0 piston or constant term	Z1^-1 tilt about y axis	Z1^1 tilt about x axis
Z2^-2 astigmatism with axis at  ±p/4	Z2^0 focus shift	Z2^2 astigmatism with axis at 0 or p/2
Z3^-3 triangular astigmatism, base along x axis	Z3^-1 3rd order coma along x axis	Z3^1 3rd order coma along y axis
Z3^3 triangular astigmatism, base along y axis	Z4^-4	Z4^-2
Z4^0 3rd order spherical aberration	Z4^2	Z4^4