Daily Image
30-11-2006
Serendipity at Work
| Submitter: | Sarod Yatawatta and Jan Noordam |
| Description: | The above figure shows a serendipitous improvement upon a common technique used in the diagnosis of radio images. It is an old trick to transform an unpalatable part of an aperture synthesis image back to the uv plane. This often leads to a clue about the causes of the artefact. In the top left hand panel, within the boxed region, we see half-rings around a peripheral source. The two remaining panels on the top row show the amplitude and phase after transformation. Unfortunately, they give no clear indication what the trouble might be. Fortunately, we did the back transformation by means of the UVBrick, which is used in MeqTrees. In the implementation by Ronald Nijboer, the UVBrick not only calculates the visibilities, but also the moving averages along the two dimensions u and v, which are used for interpolation. The amplitudes of these averages (bottom row) show very clearly that the WSRT baseline 6-C was the main culprit, and to a lesser degree baseline 6-A. Thus, quite by accident, we appear to have have found a new diagnostic tool. We need many more, so keep your eyes open. |
| Copyright: | ASTRON 2006 |
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