Instrumental Point Spread Function (PSF)
 
The instrument does spread the light in the dispersion
direction (by the echelle) and in the cross-dispersion
direction (by the prisms). The shape of one ThAr emission
lines shows how light is spread.

PSF in cross-dispersion direction:
 1. Put the pinhole in the slit (#13).
    The pinhole is 300 micron in diameter and represents
    short slit in the cross-disperion direction.
 2. Make an integration of an arc spectrum.
 3. Display the frame on ximtool, and type "imexam"
 4. Zoom in on an isolated emission line.
 5. Place the cursor on this line.
 6. Push "e". A graphical window will pop-up and
    display a contour plot.
 7. If the scale of the contour plot is inconvenient
    then go out of "imexam" by typing "q"
 8. In the IRAF window type: epar eimexam
    and change those parameters which you want
    to change. Go out of eimexam by typing "Cntrl D"
 9. Go into imexam and repeat 3...9 till you're happy.

PSF in dispersion direction:
10. Put slit #1 in the slitholder.
    This slit is longer (3.5mm) then the 
    diameter of the pinhole (3.0mm) and therefore
    less suitable to look at the cross-dispersion PSF.
    The width (90micron=0.09mm) is however much smaller then
    the diameter of the pinhole. Therefore this slit
    is very usefull to examine the dispersion PSF.
11. Go through points 2....9


last update: May 3, 2006 by ejb