National Radio
Astronomy Observatory

5.2.11.1 ’natural’ weighting

For weighting=’natural’, visibilities are weighted only by the data weights, which are calculated during filling and calibration and should be equal to the inverse noise variance on that visibility. Imaging weight w_i of sample i is given by

(5.6)

where the data weight ω_i is determined from σ_i is the rms noise on visibility i. When data is gridded into the same uv-cell for imaging, the weights are summed, and thus a higher uv density results in higher imaging weights. No sub-parameters are linked to this mode choice. It is the default imaging weight mode, and it should produce “optimum” image with with the lowest noise (highest signal-to-noise ratio). Note that this generally produces images with the poorest angular resolution, since the density of visibilities falls radially in the uv-plane

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