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Home > Astronomy > LIRIS > Cookbook - Chapter 2

The LIRIS users guide
  1. Starting the system
  2. LIRIS real time display (RTD)
  3. LIRIS mechanisms
  4. Focusing
  5. LIRIS observing commands
  6. End of night
  7. Copying data
  8. Important notes

2. LIRIS real time display (RTD)

The LIRIS real time display (RTD) consists of two elements: a RTD control panel and a DS9 window to display the data.

1. The RTD control panel.

The RTD control panel includes several options which allow the user to display either the post-read or the pre-read image extensions or the diff (=post minus pre) image of a certain observation data. Also, it is possible to display the result of subtracting one image from another (resulting in a sky subtracted image). This operation affects only the displayed data (i.e. no changes are made to the data stored on disk). Which data can be displayed depends also on the format of the saved FITS images. If you decide to store only the diff (this is the default), then you can't view the pre-read any more. More details on the data format are given here.

On the RTD control panel, from top to bottom:

  • Observation data Shows the file name of the image actually displayed in DS9.
  • Reference data Shows the file name of the image loaded as reference data (see below).
  • Status Status of the RTD. It can be ``scanning'' if the Data detection is selected to be on (clicking on the corresponding diamond), or ``data detection off'' if Data detection is off.
  • Data directory Shows the directory where the data is being stored.
  • Data detection If you click on the on box, the new images are automatically loaded into the RTD.
  • Display state This section offers several options to display the data, which are activated by clicking on the diamonds on the left:
    • OBS-REF Displays the post minus pre of the observation data minus the post minus pre of the reference data
    • OBS/REF pre Displays the pre-read of the observation/reference data
    • OBS/REF post Displays the post-read of the observation/reference data
    • OBS/REF post-pre Displays the post minus pre of the observation/reference data
  • Refresh Click on this button to refresh the DS9 display.
  • OBS -> REF Load the current observation data as reference data.
  • Quit Click on this button to quit the RTD.
  • Load OBS/REF data These buttons can be used to load any fits files of the Data directory as Observation data/Reference data: type the file name of the image in the corresponding box and click the corresponding button.
In the example of the figure, the post minus pre of the file is displayed on the DS9 window and no data has been loaded as reference frame.

2. The DS9 data display windows.
This is a typical DS9 image display window but in addition it turns red the pixels which value in the post minus pre of the data set is higher than 40000 ADU to alert observers to saturation (45000 ADU). The pixels are also turned red when either the value in the pre or in the post is higher than 43000 ADU.
Non-linearity is ~1% over the range 2000-20000 ADU (in the post-pre) . A viewgraph is available here, as well as further detector characteristics.

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Contact:  (LIRIS Instrument Specialist)
Last modified: 28 July 2011