Image processing of coronal pictures

Coronal images contain many complex, superposed, faint, optically-thin structures: Rays, loops, curved streamers, etc. The spatial resolution is often limited by the signal/noise ratio in the recording medium while the dynamic range in intensity is severely dominated by the radial gradient. The results obtained with a new simple image-processing algorithm are applied to several typical eclipse and coronographic pictures. This 2D filter (second-order difference operator in k-direction) shows superior quality by improving the signal/noise ratio, reducing the dynamic range and enhancing faint coronal structures. A comparison with results obtained with more commonly used 2D filters is also presented. The algorithm used here are briefly described, together with discussions of enhanced coronal images of coronal physics interest.