Vignetting correction for a single star-sky observation image.

We propose a method for robustly determining the vignetting function given only a single star-sky image taken by a large-aperture optical system. The actual large-aperture optical system is complex and difficult to model. Thus, the proposed method is designed to determine vignetting distortion of star-sky images without knowing the parameters or model of the optical system. This method is a model-free method by applying a polynomial regular term to the expectation-maximization algorithm to correct vignetting distortion. Unlike prior approaches to single-image vignetting correction, our proposed method, which does not rely on the optical model, gives more accurate results. The effectiveness of this technique was verified using real star-sky images captured with a large-aperture optical system (2-m telescope).