Direction-dependent Point Spread Functions (PSFs)¶
With large fields of view, the approximation of considering the dirty image as a convolution of the sky and the PSF yields a higher error.
To mitigate this error, WSClean can calculate multiple PSFs in different directions on a grid, using the parameter -dd-psf-grid
: the user can specify the number of psfs which should be fit horizontally and vertically in the image.
The -dd-psf-grid
argument only works together with the -make-psf-only
or -parallel-deconvolution
arguments:
If
-parallel-deconvolution
is used, and the number of cells in the PSF grid exceeds the number of parallel sub-images in one or more dimensions, WSClean prints a warning and reduces the PSF grid size.If
-make-psf-only
is used without-parallel-deconvolution
, WSClean uses the PSF grid as supplied by-dd-psf-grid
.If both
-make-psf-only
and-parallel-deconvolution
are not used, WSClean resets the PSF grid to 1x1 and thus disables using multiple PSFs, too.