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Deconvolution: Quieting the Noise

If an array could obtain all of the information needed to image a radio source in the sky , the resulting images would contain no distortions. Practically speaking, however, that isn't possible. All arrays have inherent limitations that hinder their abilities to gather complete information. Initial images, therefore, always contain distortions, which, fortunately, are removable through a mathematical procedure called deconvolution.

By analogy to our sense of hearing, these distortions can be thought of as a background buzzing noise in a room in which you're trying to hold a conversation with a friend. Against this buzzing noise, you might experience difficulty listening to what's being said to you. If you could just somehow remove that buzzing, you'd be able to hear better what the other person is saying.

Similarly, artifacts in astronomical images resulting from the lack of information show up as excessive brightness in images and make it difficult to pick out the object from the noise. Deconvolution removes the distortions, providing a darker background and therefore increasing the contrast between the object and the background sky. Just as you'd once again hear your friend's words clearly if that buzzing stopped, astronomers can more easily discern the object's features after deconvolution.

Cygnus A: Basic Image

This was obtained via Fast Fourier Transformation procedures.
JPEG Image (49K); Credits and Copyrights

Cygnus A: Image after Deconvolution

Cygnus A is much more well defined in this image image than in the one above.
JPEG Image (27.5K); Credits and Copyrights

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NCSA. Last modified 11/14/95