Inspect the spectra via implot

Command implot

We work in XWindows in directory /home/tcsuser

Graphical terminal - xgterm
   On the command line we write xgterm - it will open new (white) graphical terminal. Entire following work will be hold in this one.

cl
   The command cl (i.e. command language) will start IRAF

Where data are saved
   Data exposed via 700mm camera are saved to /data/ccd this we use (standard) command cd /data/ccd to change directory. It is possible to use ls to list files and subdirectories.
   Remark: If one needs to use shell commands in IRAF (i.e. in cl environment) then he should use exclamation mark to distinguish them from IRAF commands. For example, the copying file a.dat to b.dat is managed by !cp a.dat b.dat.

implot
   Now we can inspect exposed spectra. The required syntax is implot filename (it is allowed to omit extension .fit), for example implot lb040023. It will open another IRAF window with depicted spectrum. Cursor is replaced by intersection of two red lines.

   Description of axes: left vertical: exposed signal in ADU (analog digital units) in cursor position
   right vertical: y-coordinate of cursor (row on the chip)
   horizontal: x-coordinate of cursor (column on the chip)

Depiction of row or column
   We have to keep the cursor in graphical window (in the picture of spectrum). Then press the button c (column) and this will depict cross section in current possition of cursor. By the same way we can depict current row via l (line).

Depiction of row of maximal signal
is easy. Let depict an arbitrary cross section (via c), put vertical red line of cursor on the top of profile and press l. The line of maximal signal will be depicted. For ADU see left vertical axis of graph as mentioned above.

Escaping from graph
   We must be in graph environment. Press button q will return the cursor to command line in IRAF. Graphical window will be opened but inactive.

Escaping from IRAF
   is managed by command logout, the graphical terminal (xgterm) is closed by standard exit.

Another remarks

Depiction of asked column or row
   We must keep the cursor in graphical window (in the picture of the spectrum). We have to press colon and thus activate command line in the bottom of the graph (in yellow color). Then we can write commands. Put :c 1350 a depict the column number 1350. Byt the same way we can display some line, for example :l 480

Determination of the exact position of the cursor
   Pressing the spacebar will determine three numbers: coordinates of the cursor and secured signal in its position.

Zooming
   Move cursor to the left lower position of region to be zoomed and press button e. Then move the cursor to the right higher position of the region and press r. Marked region will be zoomed. To go back press tt w r.

Averaging over several rows
   Sometimes we need to decrease the noise in raw spectrum. We have two ways:

• 1. We depict the cross section of the profile and put the cursor on the maximal signal (i.e. top of the profile). Then we put the command :a 11 and finally the button l (line). Thus first of all we predefine number of averaged rows (11 in our example) and then we set that the averaging will be done around the current position of the cursor.
• 2. It is possible to select concrete number of row around which the averaging will run. We put again :a 11 and then we determine the central row, for example :l 475 . So we will average rows 470 - 480.
  
  Initial picture of spectrum (after the opening of the graphical window).
  
     
  Left: profil of the spectrum; right: spectrum along the row of maximal signal (see text and the position of the cursor on the left picture)