Image de-noising and star-recognizing are prerequisites to centroid algorithm.In view of the centroid problem,the solution adopts bi-orthogonal 3.7 as the mother wavelet to conduct decomposition in multiple levels.A Soft-threshold algorithm was employed on each high frequency level of image signal to suppress the noise components and guarantee the smoothness.Subsequently,the signal components of all levels were used to reconstruct the de-noised image.Then,a modified OTSU algorithm was performed for the star...