The Högbom algorithm

 

This algorithm proceeds as follows:

1. Find the strength and position of the peak (i.e., of the greatest absolute intensity) in the dirty image .
2. Subtract from the dirty image, at the position of the peak, the dirty beam B multiplied by the peak strength and a damping factor ( , usually termed the loop gain).
3. Go to (1) unless any remaining peak is below some user-specified level. The search for peaks may be constrained to specified areas of the image, called `CLEAN' windows.
4. Convolve the accumulated point source model with an idealized `CLEAN' beam (usually an elliptical Gaussian fitted to the central lobe of the dirty beam).
5. Add the residuals of the dirty image to the `CLEAN' image.

The fifth step is sometimes omitted, but it is recommended because it can provide useful diagnostic information about the noise on the image, residual sidelobes, ``bowls'' near the image center (see the problem of short spacings).

1996 November 4
10:52:31 EST