An IRAF routine tool called "mosdiff" is available to help MOSFIRE observers see their dithered spectra data acquired with either the ABBA or masknod algorithms. Feed it a list of images, and it will divide them into A and B pointings based on the value of the YOFFSET keyword. It averages the "A" pointings to create an A image, same with the Bs, then computes A-B.

Running mosdiff

1. Start IRAF. From the background menu on a blue desktop select: IRAF/IDL -> IRAF -> cl(*) ds9.
2. enter keck in the iraf terminal
3. enter mosfire in the iraf terminal
4. Go to a scratch area like /h/scratchspace/user (e.g. /h/scratchspace/mosfire7/). Note that you may need to create this directory.
5. In the scratch directory, create a file listing the images to analyze (call it "input.list") As an example ...

      
      /s/sdata1300/mosfire1/2013jan01/m121227_0386.fits
      /s/sdata1300/mosfire1/2013jan01/m121227_0387.fits
      /s/sdata1300/mosfire1/2013jan01/m121227_0388.fits
      /s/sdata1300/mosfire1/2013jan01/m121227_0389.fits
      /s/sdata1300/mosfire1/2013jan01/m121227_0390.fits
      /s/sdata1300/mosfire1/2013jan01/m121227_0391.fits
      /s/sdata1300/mosfire1/2013jan01/m121227_0392.fits
      /s/sdata1300/mosfire1/2013jan01/m121227_0393.fits
      /s/sdata1300/mosfire1/2013jan01/m121227_0394.fits
      /s/sdata1300/mosfire1/2013jan01/m121227_0395.fits
      /s/sdata1300/mosfire1/2013jan01/m121227_0396.fits
      /s/sdata1300/mosfire1/2013jan01/m121227_0397.fits
      /s/sdata1300/mosfire1/2013jan01/m121227_0398.fits
      /s/sdata1300/mosfire1/2013jan01/m121227_0399.fits
   

6. run mosdiff @input.lst diff.fits -> This will write the new imaged diff.fits into the scratch directory.

   you may load the image into ds9 using the file open option and navigate to the scratch directory or use the iraf command display "diff.fits."