FOCAS Mask Design Pipeline (MDP)

1. Instruction

  1. The mask design program is included in the FOCASRED package. If you have not done so, please download the package
    and extract it (using "tar -xzvf FOCASRED.tar.gz"). Follow the instruction in FOCASRED/README to install the package.
  2. To prepare the FOCAS pre-image, please follow the instruction in FOCASRED/README.preimage. The current distortion data is "DistChipDat.HPK.040919.dat". If you are using Suprime-CAM or HSC images, please convert them into FOCAS image format (see section 2 and 3).
  3. If you have a deeper image from other telescopes, you can align your deep image to the FOCAS pre-image. You can use IRAF tasks "geomap" and "geotran" for this purpose.
  4. Decide the position angle: The dispersion direction of FOCAS is vertical (y-direction in the CCDs). Hence it is better to rotate the image (using, for example, IRAF task "rotate") such that the targets are distributed horizontally. This is because you cannot change PA in the mask design procedure. The definition of FOCAS PA can be found here.
  5. Create .mdp file: See section 1.3 of the following page, MDP manual.
  6. Start the IDL program: Please check FOCASRED/setup_focasred and change the settings for
    - FOCASREDHOME : the path where you extracted FOCASRED.tar.gz
    - RSI_DIR : the path to the IDL software system.
    Copy the file "setup_focasred" to the working directory where you have your fits files and .mdp file created above.
    Execute the file:
    > ./setup_focasred
    It starts the IDL program "idlde" and FOCAS program launcher "focasmenu."
  7. In the launcher, select "MOS Design (HPK)".Two windows will show up.
    "Input Distortion File" : select DistChipDat.HPK.040919.dat
    "Input CCD Bad Pixel Table" : select badpixlst.hpk.dat
    After this, open the design image using the File tab:
    File -> Read FITS Image
    and open the .mdp file using the File tab:
    File -> Read MDP File.
    Then, select the grism using the Option tab:
    Option -> Grism Select
    and select your grism of interest (e.g. "VPH900-O58.")
    Push "Redraw" on the left side of the main window.
    If the display level is not correct, use "Change Intensity Scale" or "Auto Intensity Scale" to adjust it. You will be able to see the FOCAS field-of-view (white), the position of the slits (purple), position of the spectra (red), two CCDs with four readout channels for each (green), and the CCD gap (blue). Note that the grism VPH900 causes a horizontal shift between the slit position (purple) and the spectrum position (red).
  8. Click twice "Draw FOV" at the upper left corner of the window. Change the position of the mask center so that you have optimum arrangement of the spectra on the detector. Update the .mpd file and reload by using:
    File -> Read MDP menu.

    We recommend to update the .mdp file manually, and check the design in the above procedure #8. For the other functions of the program, please check the following page. (same as above for creating .mdp file):
  9. Output .sbr file by selecting from the File tab:
    File -> Save SBR
    and save the .sbr file. The position of the mask center will be asked again. Just push "Ok" if you don't need to change it.
  10. Take a snapshot image of the design program.
  11. Send us the following files
    1. *.mdp file
    2. *.sbr file
    3. snapshot image
    In addition, we'd like to have the fits files used in the design program so that we can double check the designs.

2. Converting Suprime-CAM image into FOCAS pre-image

    First, please download the SuprimeCam data reduction package:
    After unpacking SDFRED, you can find the script to convert SuprimeCam image into FOCAS image in the following directory:
    cd sdfred20********/clscripts/SPCAMim2FOCASim/SPCAMim2FOCASim.csh
    Executing the script without arguments will give you an instruction:
    "Usage: ./SPCAMim2FOCASim.csh [SPCAMim.fits] [Xcenter] [Ycenter] [PA(-90)] [output.fits]"
    1. SPCAMim.fits is the SuprimeCam image you want to convert
    2. Xcenter & Ycenter have to leave away from the edge of the input image by dx=1050 and dy=1080
    3. PA=-90 means no rotation; If north is up in SPCAMim.fits, enter FOCAS's PA

3. Converting HSC image into FOCAS pre-image

    The FOCAS reduction package (FOCASRED) includes an IRAF script "hsc2focas" that can convert HSC images into FOCAS pre-image. Before using the script, please make sure that the pixel scale of HSC data is 0.168"/pixel. The fits header should be:

    CD1_1 = -4.666666....67e-5
    CD2_2 = 4.666666....67e-5
    CTYPE1 = 'RA---TAN'
    CTYPE2 = 'DEC--TAN'

    if N is up and E is to the left. If IRAF is installed on a 32-bit machine, there is a image size limit (2GB). If the HSC image exceeds this size limit, please chop the image using e.g. "imcopy" task from CFITSIO. To download CFITSIO, please see:

    The script can be executed under IRAF environment by:
    cl> hsc2focas [Input image] [Output image] xc=[Xcenter] yc=[Ycenter]
    1. Input image is the HSC image you want to convert
    2. Xcenter & Ycenter have to leave away from the edge of the input image by dx=1250 and dy=1250 pixel

6 February 2020

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