For all images with a common format:

• Convert from FITS to .imh format
• SECTION the FITS images to an input list (e.g. "SECTIONS f* > inlist")
• COPY the input list to an output list (eg outlist)
• EDIT the output list of filenames to desired (e.g. fa.001 > a001)
• RFITS the images from the "fits_file" = @inlist to the "iraf_file" = @outlist

 
•  Remove bias and fix bad columns
• BIASFIX does this in one step.  The parameter file should appear something like:

                  (biassec = "[1201:1220,*]")

     (trimsec = "[2:1196,*]")
     (biasorder = 9)
     (mask = "badpix")
 
• The bad pixel mask file should be checked against a test image before running.

 

• Prepare flat-field ratio image for each aperture used
• Combine multiple flat-field images to a single image, using median filtering to remove cosmic rays and reduce noise.
  e.g., IMSUM a001,a002,a003,a004 q600_2.sum option=median
• Determine x and y boundaries of the two polarized spectra using SPLOT and edit these into POLFLAT, for example:

           orderx = 31
           ordery = 5
           (xmin1 = 2)
           (xmax1 = 1194)
           (xmin2 = 2)
           (xmax2 = 1194)
           (ymin1 = 20)
           (ymax1 = 64)
           (ymin2 = 91)
           (ymax2 = 134)
 

• POLFLAT is run interactively, adjusting the fitting orders until an acceptable fit is achieved.

• Compute a 2-D dispersion solution for each polarized spectrum
• POLID begins line identification from input centerlines of the two polarized spectra, a coordinate database file (one of those in home$linelists), and calls REIDENTIFY as well as FITCOORDS to prepare dispersion solutions.  Representative input parameters are:

           sp1line = 41
           sp2line = 111
           linelist = "home$linelists/hgcdnehear.spol"
 

• Remove cosmic rays
• This can be done in one of several ways, including my script IMCLEAN
 
• Reduce flux standards, followed by polarization standards
• POLRED is the main reduction script which:

- applies the flat-field correction
- transforms the data to a rectilinear grid
- subtracts sky background
- extracts the 1-D spectrum for each sense of polarization
- allows for correction of remaining cosmic rays
- determines flexure offset from sky emission lines
- computes Stokes parameters and total flux spectra

Here are some representative input values for the 600 l/mm red grating:
 

       image1 = "a065"
       image2 = "a066"
       stoke = "v"
       imflat = "q600_2.rat"
       outroot = "aruma_9"
       imfit = "lamp600"
       lam1 = 4000.
       lam2 = 8000.
       dlam = 4.
       invgain = 0.79
       noise = 6.
       subtsky = yes
       okvalues = yes
       delab = yes
       (nwide = 30)
       (torder = 7)
       (review = yes)
 
• Shift dispersion zero-point of standards to correct for flexure

This is done using SPECSHIFT and typically amounts to sub-pixel adjustments, using the output of POLRED.  Note that since SPECSHIFT only adjusts the dispersion solution zero-point (e.g. CRVAL1), it is 100% reversible.
 
• Compute spectral response functions

As in normal spectrophotometric reductions, these are done using STANDARD and SENSFUNC.  Note that the latter often requires a rather high spline order (13 or more) to adequately fit the bumps and wiggles in the response function.

• Reduce all other observations

This uses POLRED as per the standard observations above.
 
• Shift dispersion zero-point to correct for flexure

Using SPECSHIFT as before.

• Compute corrected total flux spectra

The task POLFLUX is self-explanatory, using the response functions computed previously.
 
• Average multiple flux spectra into one mean

Use AVGFLUX.  Note that each input spectrum is entered explicitly or via wildcards, not as a root name.