CASA dirtyimage - BHianca/VLA GitHub Wiki

  1. Open CASA and cd into the directory with the .ms/ fig35

  2. Make an image of just the calibrated GRB data. We need to separate field 2 from the other data with ms.transform() task. Specify inputs and strings and such. fig36

  3. After it is setup, hit go and execute the task fig37

  4. We can listobs() this new file to check that the field number is now reset to zero (0). This is what we will want to plot. fig38

  5. The task for making an image is called tclean(). It is quite the function and has many options and inputs. Take your time and make sure this correct. You can read through more about tclean() here https://casa.nrao.edu/docs/taskref/tclean-task.html . fig39

  6. Specify the inputs to what is shown in the terminal. One point that needs to be considered is the size of a cell and the size of the image in regards to the resolution and configuration of the VLA for a specific frequency band. See this as a reference https://science.nrao.edu/facilities/alma/naasc-workshops/nrao-cd-wvu17/Intro_CASA_Imaging.pdf . fig40

  7. Tclean() does take some time depending on the data and the inputs, so be mindful of computing time and disk space. Running this tutorial should maybe create an additional 20 GB of data from the original 14 GB data set. Keep this in mind when working with other data sets. fig41

  8. There is a simple viewer available within CASA that can look at the image made. Use the command viewer() to open the GUI and select the image file to generate a raster image of the data. fig42