National Radio
Astronomy Observatory

5.2.11.2 ’uniform’ weighting

For weighting = ’uniform’, the data weights are calculated as in ’natural’ weighting. The data is then gridded to a number of cells in the uv-plane, and after all data is gridded the uv-cells are re-weighted to have “uniform” imaging weights. This pumps up the influence on the image of data with low weights (they are multiplied up to be the same as for the highest weighted data), which sharpens resolution and reduces the sidelobe level in the field-of-view, but increases the rms image noise. No sub-parameters are linked to this mode choice.

For uniform weighting, we first grid the inverse variance ω_i for all selected data onto a grid with uv cell-size given by 2∕FOV where FOV is the specified field of view (defaults to the image field of view). This forms the gridded weights W_k. The weight of the i-th sample is then:

(5.7)

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