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UES is placed at f/11 WHT Nasmyth foci. UES has two echelles: E31 31 lines/mm & E79 79 lines/mm. Both of them give the same resolving power, but E79 gives larger inter-order spacing, which allows better sky subtraction but gives reduced wavelength coverage.


Dark slide:
Open the dark slide by hand on the entrance of the light path to the instrument. Close the dark slide by hand at the end of the night.


There are two UES autoguider fibres - a fixed fibre which views the slit (hence the SLIT fibre), and a fibre mounted on an XY probe (hence the XYPROBE fibre), which can be moved around to view light reflected from the autoguider mirror. A single command fibre-mode, or fm, is used to configure the two fibres for guiding and display. When using the new UV derotator, the unvignetted field of view is 30" in diameter. Offset guide stars can still be used as the vignetting drop off is very smooth. For example, to guide in the xyprobe fibre but to continuously display the slit fibre (eg. in order to watch the object on the slit), enter the command fibre-mode 4, or just fm 4, at the autoguider terminal.



Telescope focus:
Focusing on coarse fibre:

Determining Slitcenter:
It is important to find the slitcenter for slitguiding. Using diffused light from an arclamp might work:

Calibrate procedure:


Acquisition using coarse fibre:

Acquisition using slit fibre:

Slit guiding (up to ~14th mag):

Coarse fibre guiding --- guiding with an offset guide star:

Note: Use ICL> UPROBEVIEW to view the object on the coarse probe. If you do not see the guide star on the coarse probe, change as a test to UMIRROR GUIDEONLY. If it is there and not when you replace it with UMIRROR SHORTSLIT then the guide star is in a vignetted or obscured part of the field. Try another guide star OR if using E31 echelle with narrower < 7" dekker. Also suggest using POINTSOURCE mirror. This gives more field available to guide probe.

Arc procedure:

Tracking parallactic:
Using slit guiding you may move the rotator whenever you like, because you guide on the rotator center.

Data Handling

With Ultra-DAS use fitsinit to initialise new tapes and fitsout to write the data. Change directory to /... where the data are stored, execute the commands and follow the displayed instructions. Alternatively, use the tar command.


UES mirror:


                             FWHM      FW at 25% of M
average fov diam short:    2.4 arcmin    3.1 arcmin
average fov diam long:     2.5 arcmin    3.4 arcmin
so there should be approx 3.5 arcmin diameter field to find guide stars with the off-axis probe; on the edge of this field the guide stars are obscured by approx 1.5 magnitudes, at 1.2 arcmin away from the centre the stars are attenuated 0.7 mag. The 3.5 arcmin diameter field corresponds to about 50000 autoguider units (diameter).
Assuming that the new derotator has a throughput of 95% over its unvignetted field, and the old derotator 75% over the unvignetted field, i get that the new derotator is more effective than the old over a fov of about 80 arcsec in diameter.
So for longslit work of sources smaller than 80 arcsec the new derotator should give higher throughput, albeit with a vignetted spacial profile.
So with the new derotator we can guide over a 3.5 arcmin diameter field and do longslit observations effectively for sources smaller than 80 arcsec in extent.

Useful commands:


Measuring seeing:
The UES autoguider seeing measurement, when slit-guiding, is inaccurate because of the drop in intensity across the slit. Measuring the spatial FWHM of the spectra is the best method.

Dithering (for ues slit guiding):
In essence the DITHER command just moves the object along the slit between two extreme positions specfied by the observer. So that the use of this procedure does not interfere with the normal ICL session, a second ICL session is started.

 1) Create a DECterm on LPVS1 
 2) Start a new session to LPVG/F (see whiteboard) 

      $ LPVG (or LPVF) 
      Log in again as OBSERVER
      Answer questions as normal except : 
      Answer N to question about wanting to run observing system. 

 3) At DCL $ prompt set error message library 

      $ ICL  

 4) At ICL prompt load dither procedures

Aqui hemos usado una version modificada:

 5) Using a suitably bright star during twilight, determine the coordinates
    of the two extreme positions to be used. These coordinates must be the
    pixel coordinates sent to the TCS. With the TCS tracking, one can 
    easily determine to position but typing AUTO ON at the TCS USER> prompt
    or at the main ICL hh:mm:ss> prompt, and noting AUTO REF POSN X and Y 
    from TCS Info display. 

 6) Decide how many points you want used as part of the dither   

 7) Setup the extreme points and total number of positions, e.g. 

      X coordinate of start pixel : 195
      Y coordinate of start pixel : 95
      X coordinate of end pixel   : 205
      Y coordinate of end pixel   : 105
      Number of points (>= 2)     : 11

 8) Ask TO to acquire the object on autoguider, and put it at 
    the start position. Type GUIDE ON at autoguider and enable 
    the guide window to track the object with TRACKING ON. It 
    may be advantageous to make the guide window as large a 
    possible (GUIWIN 100 100).   

 8) Choose the exposure length (e.g. 100 seconds) and start the exposure
    with the RUN command from main ICL session. 

 9) Start the dither from second ICL session 

     ICL> DITHER 100
     ...Dither will be performed from autoguider coordinates
     ...(        195 ,         95 ) to (        205 ,        105 )
     ...in          11  points separated by  1  in X,  1  in Y
     ...with a delay of  9.090909 at each positition.
     Point           1  of          11  X=  195  Y=  95
     Point           2  of          11  X=  196  Y=  96
     Point           3  of          11  X=  197  Y=  97
     Point           4  of          11  X=  198  Y=  98
     Point           5  of          11  X=  199  Y=  99
     Point           6  of          11  X=  200  Y=  100
     Point           7  of          11  X=  201  Y=  101
     Point           8  of          11  X=  202  Y=  102
     Point           9  of          11  X=  203  Y=  103
     Point          10  of          11  X=  204  Y=  104
     Point          11  of          11  X=  205  Y=  105
 10) To abort the dither use CONTROL-C, but note that control will 
     not return until procedure is about to move to the nest position. 


UES hangs somehow:
Reset both NIU and 4MS. Both are on the UES Nasmyth platform.

UES XY handset reversed:
1) Check the UES rotator is powered on in the rack behind console
2) Do a ROT MOUNT 0 and then ZERO ROT ABS
3) Last resource, restart the TCS

UES micro overloading utility network:
There were a lot of problems with communications to UES over the utility network at the weekend. Typical problems were a continous stream of "Mimic AST overload" messages at ICL, ICL response being very slow ... Investigation showed that the system computer was receiving a stream of status messages from UES. In order to start ICL for UES you'll have to:

  1) Disconnect UES 4MS from NIU up on GHRIL platform.
  2) Start ICL
  3) When ICL has started, get ready to type command to disable monitor mode
     There's no harm is sending it before UES on reconnected to the network, you
     just get an error saying acknowledgment not received from UES.
  4) Connect UES 4MS back to NIU
  5) Type the above ICL command as soon as possible (get someone to help)
  6) Get updated UES status
     hh:mm:ss> UES_UPDATE ALL
If UES 4MS is booted, it will automatically enable monitor mode reporting, so you'll have to issue these two command at ICL. Not that when monitor mode is off, the ICL mimic does not show updated the shutter state. My recommendation is that you leave ICL up and avoid power cycling the 4MS.

No calibration light reaching the detector:
Check the following:

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Last Updated: 14 July 2001
P. Sorensen pms@ing.iac.es