DISPLAY TOOL

• 2D image display
• Datacube explorer
• Spectrum and table display

2D image display

• The main window displays the image which has been chosen using the File menu, Open function.
• The instantaneous sky coordinates of the cursor are displayed in the upper part of the display.
• The Color Map and Intensity Transfer Table are selected using the View menu, Colors function.
• The Cuts of the display are set using the View menu, Cuts function.
• The upper left windows shows the displayed zone as a small rectangle, whose size shrinks if you apply a zooming factor on the display.
• The Zoom factor is chosen using the [Z : zoom in] and [z : zoom out] buttons.
• The upper right windows allows to Pan the display window over the object, using the mouse.
• Always click on Auto set cut levels to get a good view of low-level details.
• The Select menu item is used to graphically select a spatial region of a datacube. This function is described at length in section Sky subtraction of this manual.

Datacube explorer

• Principles :
  
  This tool is provided to allow the user to check any particular spectrum recorded in a given datacube, with the help of a graphical interface allowing the easy selection of the spectrum of interest. An image, built using the Analyse data or the Image main menu item, must be provided to be used as a spatial reference frame.
  


• Use :
  
  Click on [Display] in the main menu, then on [Datacube]. The [3D explorer] window opens; it is based on RTD (see above section).
  
  
• Menus :
  
  Three menus items are provided to handle data exploration :
  
  
  • File :
    
    • Open frame : Give the name of the 2D frame you reconstructed (see above paragraph) from data recorded into the datacube to be explored, or from data recorded into any other datacube linked to the same mother table. This frame will be used as spatial reference. As soon as it is loaded, the instantaneous sky coordinates of the cursor are displayed in the upper part of the display.
    • Open datacube : Enter the name of the datacube you want to explore. Once the datacube is opened (the idle time at the beginning of the operation is normal : it corresponds to the time needed by the program to build a correspondance table of sky coordinates and lens numbers). Then, if you left-click on any point of the displayed reference image, the nearest lens is found, and the corresponding spectrum is displayed in a graphic window. The number of the lens/spectrum is displayed, too. This is extremely useful, at the end of the reduction process, to identify any spectroscopic defect (abnormal spectra, undetected cosmics, ...) which shows up on reconstructed images, or to wander through the local spectral characteristics of an extended object...
      
    • Clear : Clears the display windows of the reference image frame.
    • Exit : As you may guess...
  
  
  • View :
    
    • Colors : Use this to set the lookup table (LUT) of your choice. Rainbow and heat are among the favourites... Some of the ugliest LUTs ever designed are provided, you will soon notice. You may, too, choose the intensity transfer table (ITT), and use either Log or Ramp (linear) level encoding.
    • Cut levels : Use this to set the cut levels of the display.
    • Cuts : Use this to draw a line through the 2D frame, and then plot the object profile along this line.
    • Pick object : Use this to isolate a square area of the 2D frame (set the window size with the Sampling size cursor), and obtain various informations regarding this area : position, intensity and FWHMs of the peak enclosed in the window, statistics, ...
    • FITS header : Use this to list the FITS header of the displayed 2D frame.
    • Lenses : an XOasis special. If you click on that, you get the complete figure of the lens array, superimposed over the reference image. Usefull, but may be a complete mess if you forget to zoom in before.
  
  
  • Graphics :
    
    • Toolbox : Use this to improve the image displayed adding lines, arrows, shapes, labels, and so on, before capturing the display.
    • Clear : As you guess, clears the graphic overlay.
  
  

Spectrum and table display

• Principles :
  
  This tool is used to plot various quantities stored into datacubes, 1D spectra, or tables. Note that successive plots may be overlaid using the Overplot function instead of Plot. Line styles and colors may be changed at will.
  


• Use :
  
  
  • Click on [Display> in the main menu, then on [Spectrum and table]. The Graphics display window pops up.
    
  
  
  • Use the File menu item to load the file you want to plot :
    
    • Plot datacube : as a datacube cannot really be plotted as a whole, the user is asked to give also the number of the lens for which the spectrum will be displayed. Instead of the spectrum data, one may ask for a display of the Noise variance, or of the S/N ratio.
    • Plot spectrum : this time, the name of the 1D file has to be entered into the input field.
    • Plot table : enter the name of the Table to plot, of the two data columns (X taken from column... and Y taken from column...). You can choose the Symbolshape and the Symbol size used for each data point, or use the content of a column to mark the position of each data point (Label each data point with column...). As an example, to plot the lenses map, use as Table to plot the main table of the exposure, created at spectra extraction. Set X taken from column... = A, Y taken from column... = D, Label each data point using column... = no, and click on Plot with label. May not be very readable, as there are quite a lot of lenses... Use the zoom function : left click and hold, drag the window, release the left button; yes, like in Windows (Ooooops! Copyright, trade mark, and so on...). Right click to de-zoom.
      
    
    
  • Use the Options menu item to set the following :
    
    • Set bounds : enter the four values which must limit the plot area. Click on Done. Click then on Man X and Man Y at the bottom of the Graphics window, and replot.

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