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How to display and process images at the JKT

Last updated 4th Dec 1998

The JKT DAS runs on the Sparc 5 known as lpss12. This computer is not powerful enough to gather the data from the CCD and carry out data reduction at the same time. This is also the reason that netscape can't be run on this machine. To the left of the DAS computer is the system computer, currently lpss10, that is used as the data reduction machine.

The data is stored on lpss12 in the /obsdata/jkta or /obsdata/jktb data partitions. These directories have the same names on lpss10. A new directory is created each day about midday, eg. /obsdata/jkta/19991028. The observing data, stored in FITS format (with extension .fit), can be written to the C- or D-tape with fitsinit and fitsout. With the latest version of IRAF it is not necesary to convert the FITS files to IRAF format if you want to display them. Scratch space (not the /obsdata partitions !) should be used for converting FITS files to IRAF format image files or for data processing.

This note sets out the steps to setup for analysing data.

Data Reduction

  • Log on to the JKT reduction system lpss10 as user jktguest.
  • Make a directory for the scratch data where the IRAF files go with:
    mkdir /scratch/jkta/yymmdd (eg. mkdir /scratch/jkta/19991028 ). If this directory already exsists then use an alternative, eg. mkdir /scratch/jkta/19991028a
  • Go to your home directory by typing cd ~ if you are not already there.
  • Use the right mouse-button background pull-down window to open an XGTERM, or open it by typing at the command prompt in your main window: xgterm &
  • Use the same pull-down menu to open an XIMTOOL image display tool, or start it up from the command line with ximtool &
  • In the XGTERM start up IRAF with the cl ommand, and when in IRAF load the ING package by typing ing
  • In IRAF move to the scratch directory that you created: cd /scratch/jkta/971028
  • In IRAF set the correct path for the das_get IRAF command by editing the IRAF parameter table: epar das_get. Set the obsdata path to /obsdata/jkta/971028. Use ctrl-D to save and exit the epar task.
  • Make an exposure on lpss12. Make certain that the run has completed reading out and that the headers have been transfered.
  • At the IRAF command prompt type das_get to retrieve the image. The command line options for the das_get task are explained in the help file; type help das_get in IRAF to see the available options.
  • Use IRAF task imexamine to check the quality of the image. Some single key commands are available in the XIMTOOL window: "l" line plot, "c" column plot, "m" for box stats, "j", "k" and "r" for Gaussian fits and for FWMH, "q" to quit and return to IRAF.
  • Another powerful and useful IRAF task is implot. When the red cross hairs are active in the XGTERM display window, you can make a hardcopy by typing = (an equals sign).
  • Help on any IRAF command can be obtained with the help feature (e.g. help das_get).

For further help on IRAF there is an introduction in the black folder Unix DAS Users Manual in the control room.

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Contact:  (Head of Astronomy)
Last modified: 18 December 2010