Image enhancement for the observation of the solar corona

摘要

In this work, we introduce an image enhancement method ideally suited for the visualization of coronal intensity images. The steep radial gradient of the coronal brightness is adjusted by normalising the coronal image with the Fourier approximation of its local average. A method based on deconvolution and localised normalising of the data at many different spatial scales is used to further enhance the fine structures, and a wavelet shrinkage denoising method is used for noise suppression. The effectiveness of this method is demonstrated on a series of images observed by various instruments including spacial and earth-based coronagraphs as well as photos during total solar eclipse. This method is very helpful for qualitative analysis of solar coronal structures that are mostly invisible on original images.