Keywords: imager

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## Imaging/deconvolution: a brief sequence of commands

For the user, [rgb]1,0,0IMAGER reduces the number of actions to the strict minimum. The imaging sequence is always the same:

        1- Reading data
           READ UV MyData.uvt /RANGE Min Max Type
           ! here, optionally use UV_TIME, UV_COMPRESS, UV_BASELINE to average data
           ! or UV_FILTER, UV_CONT to filter lines or remove continuum
        2- Imaging
           UV_MAP
        3- Deconvolving
           CLEAN
           ! here, optionally use UV_RESTORE
        4- Looking at the result
           VIEW CLEAN      ! or SHOW CLEAN
        5- Writing the result
           WRITE * MyData

- Step 1: Reading the specified internal buffer (here UV) from the input file (cyan`.uvt` file type), loading only the channels falling in the range defined by the variables Min and Max, of Type magenta`CHANNEL`, magenta`VELOCITY` or magenta`FREQUENCY`. [rgb]1,0,0IMAGER recognizes whether the UV table is for a single field or a mosaic. The only difference between the single field and mosaic cases is that [rgb]1,0,0IMAGER yields a Sky brightness image for Mosaics, while the computed sky brightness of a single field is not automatically corrected for the primary beam attenuation. Imaging for multiple fields will be presented in Section . Single Dish data can also be loaded in the following way : magenta`READ SINGLE` cyan`File`.
- Step 2: Computing a dirty map and beam from a UV data. magenta`UV_MAP` processes single fields as well as Mosaics.
- Step 3: Deconvolving the blue`DIRTY` image map (a Single-field or Mosaic) using the dirty blue`BEAM` with the current blue`METHOD`. The default for the SIC variable blue`METHOD` is magenta`HOGBOM`, the other supported methods being magenta`CLARK`, magenta`MRC`, magenta`MULTI` and magenta`SDI`. See magenta`CLEAN ?` for the other SIC variables controlling the deconvolution process. The outputs are the blue`CLEAN` and blue`RESIDUAL` images, and the Clean Component Table blue`CCT`, all being stored in dedicated SIC variables.
- Step 4: Plotting the result in the specified internal buffer (blue`CLEAN`). Optionaly, the user can restrict the plot to a subset of channels through the optional arguments First and Last. magenta`SHOW CLEAN` can also be used instead, and produces a different type of plot.
- Step 5: Writing all modified image-like buffers (not the UV tables) under the common file name ''cyan`MyData`''. In the case of the present example, the following files are produced: cyan`MyData.lmv, MyData.lmv-clean, MyData.cct, MyData.beam`, which correspond to the buffers: blue`DIRTY`, blue`CLEAN`, blue`CCT`, and blue`BEAM`, respectively. magenta`WRITE UV` cyan`MyData` would only write the internal buffer (blue`UV`) in the file cyan`MyData.uvt` (the default extension corresponds to the specified buffer data type).

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