In order to analyze data of dual frequency observation,
the size of the beams have to be made same before taking ratio.
The method is as follows,
IDL> norh_rd_img,file0,index0,data0 
CR
IDL> norh_rd_img,file1,index1,data1 CR
IDL> norh_convol,index1,index0,data0,index0c,data0c CR
By norh_convol, data data0 is convolved by a beam
associated with index1. The pixel size of the result array
data0c will become the coarser one between the beam and the image.
Similarly,
IDL> norh_convol,index0,index1,data1,index1c,data1c CR
then data0c and data1c have the same beam and
the same pixel size.