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1.1.4 Open a new image with this imagepol tool


Before polarimetric analysis can commence, an image file must be attached to the imagepol tool using the open function. Also, use this function when you are finished analyzing the current image file and want to attach to another one. This function detaches the image tool from the current image file, if one exists, and reattaches it (opens) to the new image file.

The input image file may be in native CASA, FITS, or Miriad format. Look ?? for more information on foreign images.

The input image must have a Stokes axis. The exact collection of Stokes that the image has, determines what the Imagepol tool can compute. Stokes I, Q, U, and V refer to total intensity, two components of linear polarization, and circular polatization, respectively. Therefore, if you ask for linear polarization and the image only has Stokes I and V, you will get an error.

The input image may contain data at many frequencies. For example, the image may be a 4D image with axes RA, DEC, Stokes and Frequency (order not important) where the Frequency axis is regularly sampled. However, the image may also contain many frequencies at irregular intervals. Such an image may be created with the Image tool function imageconcat. It enables you to concatenate images along an axis, and it allows irregular coordinate values along that axis.




image file name or image record (generated by ia.torecord())







print "\t----\t open Ex 1 \t----"’stokes.image’)  
The {\stff open} function first closes the old \imagefile\ if one exists.  


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