Image Processing

Digitized pictures allow the use of the computer to enhance certain information in the raw data. I have two examples here. In the first one the brightness decrease on the disk of the planet jupiter is to be compensated for. Why is this necessary ? The contrast of some cloud structures on jupiter is in a very small brightness intervall. If I take this intervall as it is at the center of jupiter's disk then the brightness of the edge of jupiter will be out of this range and therefore detail in those areas won't be visible. It is advised to have the brightness variation due to edge darkening removed from the picture prior to enhancement of cloud structures. For this purpose a small programm was writtem that simulates the brightness variation on an arbitrary ellipse.

This is an example:

A. Nikolai

10cm refractor raw data 

The mask fitted to compensate for the brightness variation across the disk. 

Raw data divided by the mask. 

Contrast streched to optimum. 

Solar eclipses

Another area where compensation of large brightness variations is interesting is in total solar eclipse photography. The solar corona visible during such an event has a very large brightness gradient. Small radial brightness variations are drowned in the overall brightness distribution an become invisible at first. 

D. Hartmann

raw data from 256 digitized video frames. There are no radial streamers visible. From this picture a radial filter mask was produced. 

The radial mask. Only large scale structures are visible. 

The raw picture was divided by the mask and streched to the optimum contrast range. 

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