Rebinning multiple datasets

On many occasions it is necessary to combine multiple observations into one regridded image to attain the desired signal-to-noise for a source map. One way of doing this is to enter into rebin (or related task) each map in turn along with the WEIGHT, SHIFT_DX and SHIFT_DY. For a small number of input sets this approach is fine but for large numbers (n $>$ 2) this approach becomes tedious and error prone. In order to overcome this problem the rebin tasks can accept an ASCII text file as input as well as an NDF.

This text file contains information on one input set per line. This line must contain either a space separated list of with the NDF, weight, shift_dx and shift_dy, or the name of another text file:

# Regrid text file for 3c279

# Format of text file should be
#  NDF     WEIGHT     SHIFT_DX    SHIFT_DY

n59_reb_lon  1.0   0.0   0.0    # Map 59
n60_reb_lon  1.0   1.0   0.0    # Shift 1.0 relative to n59

n61_reb_lon{i2} 1.02            # Only want the second integration from
                                # this -- shifts will be requested when
                                # the text file is included
n62_reb_lon   0.98 1.0   2.0    

3c279_old.bat                   # Include previous 3c279 data via a text file.

From this example we can see that blank line are ignored and a `#' indicates the start of a comment; all text on the line after the `#' is ignored. Not all the parameters need to be specified on the input line; if they are missing the software will simply ask for the values from the user. The order of these parameters is important so it is not possible to specify map shifts without specifying a weight - similarly SHIFT_DY can not be given without SHIFT_DX. Also note that the NDF name can include SCUBA sections. Even though text files can include other text files a recursion depth of 5 has been hard-wired into the code to prevent abuse - it was felt that this should be sufficient in most cases.

With the default messaging level, rebin tasks always show a summary of all the input data before proceeding to the final regridding - this can be used to check that the correct files (and associated parameters) have been read in.