CASA cleanimage - BHianca/VLA GitHub Wiki

  1. Open CASA and cd into the directory with the dirty image you have produced and open the viewer() fig48

  2. We need to select the dirty image raster from the previous steps fig49

  3. Going to have to really zoom in on areas where there are side-lobe artifacts. Those radiating features from bright sources are what we want to eliminate, so in order to do so we need to tell clean() what is real emission and what to ignore in our FOV. fig50

  4. This double lobed radio galaxy like feature is a good place to start in the upper right. Zoom in even more so that we can just see the emission from a small concentrated source. fig51

  5. When you are zoomed in like this, we are going to draw a polygon around the real source emission. Use the draw polygon region tool around. fig52

fig53

  1. Do this for all of the sources in your FOV. Then export the regions as a file. fig54

  2. Now tget tclean() from before and add some options. We are going to increase the iterations to 100000. We are also going to reference the region file we made and set a noise floor for cleaning. fig55

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fig57

  1. Here is what cleaning a dirty image looks like when finished. The same power color scaling was used but note how the artifacts are no longer visible. fig58