TCS 220 Pointing Procedure

Pointing measurement procedure steps for FEROS, WFI and GROND

  1. Determine by instrument either the Optical Axis or define the SCIENCE reference position proyected on their corresponding guiding camera.
  2. WFI: Reference pixel
  3. FEROS:fiber on IMG camera
  4. GROND: reference pixel in visible camera translated to the IRTD camera
    1. On the TCS-SETUP panel define pointing on SCIENCE
    2. Use TCS panel and point to any FK5 star around zenith
    3. Take an image with WFI to check centering. Once centered, set the Feros M3 mirror IN to see the star on the FEROS guiding camera. For GROND of course, move new M3' mirror IN to see the star on it.
      WFI reference should be +/- on the telescope optical axis, for FEROS and GROND there will be and offset due to the fiber position for FEROS, detector position for GROND and the corresponding M3 positions.
    4. Define the current WFI proyected star pointing as the reference position (like the fiber position definition) or just define the corresponding guiding camera center as the instrument reference.
    5. If star is not in the field DO manual search and measure the offsets to correct the ID and IH terms (Correction Coordinates)
    6. Do the ID and IH value entry on TCS-SETUP panel
    7. Note: Thi should only be needed after a major optics or mechanics intervention
  5. With the new offset try new presets around zenith before starting the measurement sequence

Pointing Measurments Sequence

Open the following panel as follow:

  • On HOST w2p2tcs, USER tcs open a xterm and type e2p2opsPomMes &.
  • FEROS: On HOST w2p2tcs, USER cam open a xterm and type e2p2opsRtd2 &.
  • WFI & GROND: use the instrument RTD

e2p2opsPomMes Panel Setting and Actions

To get full image just click here

  1. Press Load Catalog to load Stars Catalogue (Use fk5.tcs)
  2. Press Load Temp.. to load any of the following template files:
    1. 220PointingTemplate.tpl
      ( more than 50 points)
    2. MeridianSixStars.tpl
      (quick ID,CH measurement)
    3. pomTemplate24.tpl
  3. Press check button Auto Name (Checked by default, just leave it).
  4. Press button Create file
    (Output error file).
  5. Set DUT ( not used for 220).
  6. Check radius = 100 arcmin (leave it)
  7. For WFI and FEROS, check button Auto Preset (Checked by default, just leave it).For GROND, uncheck
  8. Check button Auto Store(Checked by default, just leave it).

On e2p2opsRtd2 Panel

(Not tested yet, may be the offset signs and rotation are wrong. Use the guider camera RTD and try manual offsettings .
FEROS RTD has already implemented the reference definition and the offset command with the CENTERING button)To get full image just click here

  1. Select Camera (WFI FEROS GROND ?...)
  2. FEROS: Select Centroid method (Standard, Threshold, none)
  3. Press TCCD Setup Button
  4. Check Camera button ON (Guiding camera have to be in infinite loop)
  5. Adjust image scale and cuts using Autocut and Scale buttons
  6. FEROS:In the Reference Position entry fields, write the X,Y coordinates and press
    button "Draw Box".
  7. Box size by default is 20pix.
  8. WFI & GROND: use Graphic Tools to draw a box


  1. On panel e2p2opsPomMes press button Next Object to start the sequence measurements. An automatic searching procedure - according to the template file - will get the Telescope coordinates and will move it to the first one on list.For WFI and FEROS as the auto Preset and store commands are set, do not go through the list. For GROND, select a star fainter than magnitude 5 and click Preset button.
  2. Wait both telescope and dome preset done i.e Guide then Feros:on panel e2p2opsRtd2 press button ObjectToBox and move cursor to the target and click on it. Offsets will be applied to the telescope to bring the star on the reference position.WFI and GROND: calculate the offsets to move tge star to the reference position and appl

    NOTE: If the start is not on the TCCD field, just press buton Next Object. This action will produce an error equal cero on the measurement file because the preset and corrected position will be the same and it won't be taken in account for the pointing analysis.
  3. On panel e2p2opsPomMes press button Next Object
    This action measure the telescope position and save it into the file before going to the next target from the template file list. A tail window on the error file will be open and a tpoint FIT will be done and displayed by new line in the file. Fit is done using the current 220 poinitng terms (ID,IH,CH,NP,ME,MA,FO,TX).
  4. Repeate points 2 and 3 to complete the template list.

  5. To finish press Close File

On Line Pointing Analysis

Once the measurement sequence has being finished.To get full image just click here

Press button 220StdFit to run the 220 tpoint procedure fit. Check the new graphic panel with the pointing error fit and the xterm to see the RMS result. If there are points to edit use button SLIST and MASK to list residuals and to mask bad points. Suggested option is: mask R > 30

Stand-alone Pointing Analysis (tpoint command line)

Because TPOINT 7.8 version bug, remember that the MA terms has the wrong sign.

  1. Open a xterm
  2. cd /vltdata/pointing
  3. Look for the last data file name just typing ls -1tr DATA/*
  4. tpoint
  5. indat DATA/[--lastdatafile--]
  6. call 220ESO
  7. slist to list residuals
  8. To edit points use mask r 50
  9. Use fit to fit the new slist
  10. call e9 to plot residuals

Apply Model

To apply the tpoint model, all terms have to be multiplyed either by -1 or +1, and be added to the current terms values. First just try the IH, ID on the TCS-SETUP panel and do telescope preset to know which sign have to be used.

If the sign is negative then MA must be added with the same tpoint sign. else it should be multiplied by -1