Uniform keV ion irradiation causes a morphological instability known to result in the spontaneous formation of topographic ripple and dot patterns. The degree of order of these patterns, which has important implications for non-lithographic patterning applications, varies markedly with fabrication conditions. We investigate the influence of systematic variations of fabrication conditions, including current density, ion fluence and ion energy, on the degree of order of argon ion bombarded Si(111) surfaces. For quantifying order in sputter rippled topographic images, we develop an algorithm that evaluates the density of topological defects, such as ripple bifurcations and terminations, and suitably normalizes the result in order to present a scalar figure of merit: the normalized defect density. We discuss fabrication conditions that lead to extremely well ordered dot and ripple patterns upon irradiation.