235 MHz $--$ Our Methodology and use of AIPS

The visibility data file of the 235 MHz data was made of 5 channels each of which had 9 original channel averaged generated by the task SPLAT. This single source file was used as input to the IMAGR using the task SPLIT.

Since the sky is non-coplanar at low radio frequencies because of wide primary field of view, it is required 3D inversion. To correct the w-term effect (see section 3.3.2.7), the sky is divided into smaller portions, called as FACETs. The appropriate RA and DEC shifts for the center of each FACET, were computed using the AIPS task SETFC. Typically this resulted in a 5 $\times$ 5 grid of FACETS, each of size 512 $\times$ 512 pixels.

The map was made of the region of $\approx$ 3.5$^\circ$ using the parameters; CELLSIZE=5,5; IMSIZE=512,512; NFIELD=25; NITER=10000; NCHAV=5; OVERLAP=2. Default values used for the remaining parameters.Where, CELLSIZE is the pixel separation in arc second, IMSIZE is the size of the each field in pixels, NFIELD the number of fields to map in the antenna beam, NCHAV is the number of channels to be averaged together in the griding process, OVERLAP is to force all images to be recomputed with filtering every N (in this case 2) CLEANs.