Sometimes also called the smoothing function or density weighting function.
- Inverse variance weighting: Optimizes the SNR ratio in the final image. This option is not, however, implemented
in the AIPS task MX.
- Natural weighting: synonymous with unity weighting
- Super Uniform: Increases the size of the cell to which uniform weighting is applied. Gives lightly sampled
isolated cells weights comparable to those in the most heavily sampled regions. This further reduces the SNR over normal
uniform weighting.
- Uniform: Each visibility assigned to a grid point is weighted by the inverse of the number of visibilities
assigned to that point. This choice of weighting makes the sampling of the UV plane appear to be more uniform. For
example, for a single dish, the number of baselines as a function of baseline is linear with a negative slope, passing
through the point . Uniform weighting makes the SNR worse by 1.25, but the beam becomes sharper. The
resulting beam is specified largely by the tapering function.
- Unity: Each visibility is given the same weighting. This gives the best SNR for detecting weak sources.
However, since uv tracks tend to spend more time per unit area near the origin, unity weighting emphasizes the data
from short spacings and tends to produce a beam with a broad low-level plateau.
© 1996-2007 Eric W. Weisstein
