1. Starting the system
2. LIRIS real time display (RTD)
3. LIRIS mechanisms
4. Focusing
5. LIRIS observing commands
6. End of night
7. Shutting down the system
8. Writing data tapes
9. Important notes
    

5. LIRIS observing commands

A complete list of all available LIRIS user commands is available.
A complete list of the UltraDAS commands can be found in the UltraDAS command dictionary.
In the following we summarise the most often used commands. They should keep you running throughout the night.

• Selecting the desired LIRIS configuration
  For the options see the predefined configurations page.
  • Imaging mode. Type:
    SYS> limage <option>     options+details
    For polarimetry, insert the Wollaston prism with lfwheel1|2 <prism name> .
  • Spectroscopy mode. Type:
    SYS> lspec <option>      options+details
    DO NOT FORGET TO INSERT A SLIT MASK WITH lslit <slit mask name> .
    
  • Coronography mode. Type:
    SYS> lcor <option>       options+details
  • Polarimetry mode. Type:
    SYS> lipol <option>      options+details
  • Calibration mode. Type:
    SYS> lblanks             options+details
    Use this for obtaining darks and at the end of the night.
     
• Getting exposures
  
  • SYS> run liris <int time> ["title"]
    SYS> multrun liris <N> <int time> ["title"]
    The run command takes an exposure and saves it to disk.
    With multrun N exposures are taken.
  • SYS> glance liris <int time>
    SYS> multglance liris <N> <int time>
    Same as the run command, but the exposure is saved as s1.fit and overwritten with by the next call to [mult]glance. Useful to check the target position or for finetuning the object position.To position an object onto a slit, use the multglance command as outlined above. In addition, from the DS9 data display window select the according mask and overlay it over the data shown. You do this by selecting the according (multi)slit mask from the RTD control window.
    

    Example 1

    Example 2

    Remark: The overlaid polygon which is shown then on top of the exposure is actually an image of the according slit mask that was taken with LIRIS itself. The exact slit position and orientation in this image was determined automaticallyby SExtractor. All this guarantees that the slit shown is indeed at this position. You can cross-check the positioning after finetuning by actually inserting the slit mask into the beam with lslit <slit mask name>. Then take another image and look for the object in the slit.
    The same procedure holds for multislit masks, but there you should use the reference holes and the according stars. 
  • SYS> dark liris <int time>
    Takes an image and set the OBSTYPE header parameter to DARK. You have to call lblanks before taking darks in order to close the light path.
  • SYS> multdark liris <N> <int time>
    Same as run but repeats the dark sequence N times and generates m output files.
    
  • SYS> flat liris <int time>
    Takes an image and set the OBSTYPE header parameter to FLAT.
  • SYS> multflat liris <N> <int time>
    Same as flat but repeats the run sequence N times and generates m output files. 
  • SYS> scratch liris <k> <int time>
    Takes an image and saves it in: sk.fit. k is an integer within the range 1-99. The scratch file sk.fit is overwritten when a new scratch <k> is taken.
  • SYS> multscratch liris <N> <int time>
    Same as run but repeats the run sequence N times and generates m output files.
     
• Guide stars
  The TO will select a suitable guide star for you. Keep in touch with him and let him know if your exposures require guiding.
  When taking spectra, make sure that the telescope is guiding and that your target is on-slit before starting the exposure.
  Let the TO also know the extent of the dither offsets you will make so that he can choose an appropriately sized guiding window to avoid the loss of the guide star.
   
• Data storage types and read modes
  
  • SYS> rmode liris mndr <Nr> <Nav>
    Sets the number of multiple non-destructive reads (MNDR) to Nr and the number of averages to Nav. Nr is the number of times that the array is read non-destructively prior and after an integration period. The array data from the Nr pre- and post-integration reads, respectively, are averaged independently. Nr is an integer between 1 and 16 (default is 1; i.e. double correlated sampling). Nav is the number of accumulated exposures that are averaged and written as a single output file.
    We recommend to set Nr = 1 for imaging and Nr = 4 for spectroscopy, since in the latter case the readout noise becomes dominant over the sky background noise.
  • SYS> coave liris <Nav>
    Sets the number of averages to Nav.
  • SYS> storemode liris diff
    Saves FITS file with one extension. It contains the difference between the post-read and the pre-read. This is the recommended storemode.
  • SYS> storemode liris diff_pre
    Saves FITS file with two extensions. The first contains the difference between the post-read and the pre-read, the second one the pre-read itself.
     
• Imaging scripts
  
  • SYS> [ag_]mdither<2...9> <N> <int time>
         ["title"] [-nruns=num_runs] [-xoffset=xoffset]
         [yoffset=yoffset] [-jitter=jitter_size]
    Moves the telescope to 2 to 9 dither positions. Prepend "ag_" at the beginning of the script name if you are using the autoguider. At each dither position nruns images are taken with the specified integration time. The dither pattern is repeated N times. The size of the pattern is given by the xoffset and yoffset parameters (in arcsec, defaulted to 12"). In all cases the telescope starts and ends at the centre of the pattern. If you repeat the pattern several times, you can set the jitter parameter to a value larger than 0. The staring point of the next cycle will then be randomly offset with respect to the first cycle in a jitter box of the specified size. See here for more details.
     
  • SYS> [ag_]mdither<2...9>ext <N> <int time>
         <sky offset> <pa_offset> ["title"]
         [-nruns=num_runs] [xoffset=xoffset]
         [yoffset=yoffset] [-jitter=jitter_size]
    Same as [ag_]mdither<N>, but goes to a blank sky position after one cycle. The offset of the blank position with respect to the target is specified by sky_offset in arcsec and the position angle (pa_offset). See here for more details.
     

• Spectroscopy scripts
  
  • SYS> [ag_]spec_nod <N> <int time> ["title"]
         [-nruns=int] [-offset=int] [-jitter=float]
    Moves the object between two positions (A,B) along the slit. Prepend "ag_" to the script name when using the autoguider. Positions are separated "offset" arc seconds. Assuming the object is centred on the first position A = (0,0) , the first exposure is taken there and the second one at B = (0, offset). See here for more details.
    The nruns parameter determines how many images are taken per nod position.
    The jitter parameter triggers that the A and B positions are randomly generated to lie within a segment that is centred at each position. The dimension of the segment is given by the jitter argument.
    If N is larget than 1, then the pattern is repeated as follows (example: N = 5):
    AB BA AB BA AB.
     
  • SYS> ag_spec_ext <N> <int time> <sky offset>
         ["title"] [-nruns=int] [-jitter=float]
    Switches the telescope between the OBJECT and the SKY.  Exposures at OBJECT positions are done with the autoguider ON.
    If the pattern is to be repeated (N > 1), the SKY positions are randomly generated to lie on a 15 arcsec segment perpendicular to the slit centred at (sky_offset, 0). At each position nruns images are taken.
    If the jitter option is used, the OBJECT positions will be randomly generated to lie within a segment of "jitter" value size along the direction of the slit.
    For N = 4,  the acquisition pattern is as follows:
    Obj Sky₁   Obj Sky₂  Obj Sky₃   Obj Sky₄
     

• LIRIS diagnostic commands
  • SYS> detstat Shows detector status and temperature of the monitoring points.
  • SYS> lmchstat Shows mechanisms and LIRIS controller status.
      
• TCS commands (usually done by the telescope operator)
  • user "ENTER APERTURE <number> <ra offset> <dec offset>"
    Defines the aperture < number> characterized by <ra offset> and <dec offset> arcsec offsets in RA and DEC respectively (e.g. user "ENTER APERTURE 1 -400 0")
    
  • aperture <number>
    Offsets the telescope according to the previously defined aperture.
    
  • offset arc <ra offset> <dec offset>
    Offsets the telescope by <ra offset> arcsec and <dec offset> arcsec in RA and DEC respectively from the nominal position. THIS IS ALWAYS AN ABSOLUTE OFFSET, NOT A RELATIVE ONE!
    
  • gocat <object_name>
    Moves the telescope to the object <object_name> if this has previously been loaded into the TCS.
    
  • object <object_name> <ra(hh mm ss.ss)> < dec(dd mm ss.ss)> <equinox>
    add
    Adds the object <object_name> to the catalogue.

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