We report the first detailed measurement of multiple (up to twenty) diffraction rings due to a laser beam traversing a nematic liquid crystal cell. Experimental measured intensity distributions are in good agreements with numerical calculations based on the diffraction theory, taking into account the spatial self-phase modulation effect, the two-dimensionality of the problem, the wavefront curvature effect and the non-local response of the nematic liquid crystals. The individual contributions of the aforementioned effects on the far-field pattern are clearly illustrated.