Science Operations

Longslit Spectroscopy

Contents

  1. 1 Acquisition – Faint target
  2. 2 Acquisition – Bright target
  3. 3 The LS_2.0_1.5_arcsec Mask
  4. 4 Two Target Acquisition

Note: Please do not leave the mask in turnout for long periods! Motor current is used to hold the mask in this position and over time it will warm up parts of LUCI.


Spectroscopy (both Longslit and MOS) scripts are comprised of an acquisition component and science component.  The following will descibe how to set up the acquistion for long slit spectroscopy.  

Acquisition – Faint target

    1.  “Load” the Observing Script into the Observation Execution GUI
    1. Once the script has been loaded into the Observation Execution GUI, confirm with the OSA that it is safe to slew to the target
    1. Select the “GO!” Queue Action Button. This will send the telescope preset and instrument configuration. The filters, camera, etc. will move into place as the telescope slews into position.  Once in position, the predetermined guide star will be acquired by GCS.

      The telescope will collimate, and once the wavefront sensor error WFE (circled above in the GCS GUI) is below ~800 nm, LUCI will proceed with executing the observations.  The first obsitem will be a sky image.  This is an image offset from source nominal position. The second obsitem will be the source taken at the original position.  The third obs item will move the mask into the FPU and take an image of the mask.
    1. Select the Long slit tab in the RTD GUI

    1. Confirm the auto-populated filenames for alignment (source) and background (sky) in the target selection section are correct, then click “Subtract Images”.
    1. In the Aladdin display, click on your source. You can zoom and click multiple times to get reasonably close to centered on your target. Use the Finding Chart provided by the PI to ensure you select the correct source.
    1. Click “Set1” then center target position(s) to centroid on your source.  Confirm the red ‘+’ is in a believable position.
    1. Confirm that the thru slit image is populated into the Slit Selection and with this determine the position in the slit where you would like to center your object:
      1. Still in the Long slit tab of the RTD GUI, Confirm the auto-populated filename in the slit selection section is correct, then
      2. In the Aladin display, click on your slit. You can zoom and click multiple times to get reasonably close to centered on your target.
      3. If you want your source centered at Y=1024, check the Use fixed Slit1 Y position box or change the Y coordinate where it will center your source.
      4. Click set then center slit position to centroid on your slit
    1. Calculate the offset from source to slit and send that offset to the telescope. To do this click “Calculate” in the Long slit tab. Confirm that the offsets make sense, then send if they do. This will insert an offset ObsItem into the queue.
    1. Click “GO!” on the Observation Execution GUI. This will execute the alignment offset, take the source+slit image and then pause the queue.
    1. If you are happy with the source alignment on the slit, click “GO!” again to start executing the spectroscopic portion of the script. If not, you may manually execute a small offset on the Telescope Service GUI and take another image to confirm your source position in the slit. Manually take the other image using the RMGUI. Once acquired, the science portion of the script will run.

Acquisition – Bright target

    1. “LOAD” he Observing Script into the Observation Execution GUI.
    1. Once the script has been loaded into the Observation Execution GUI, confirm with the OSA that it is safe to slew to the target
    1. Select the “GO!” Queue Action Button. This will send the telescope preset and instrument configuration. The filters, camera, etc. will move into place as the telescope slews into position.  Once in position, the predetermined guide star will be acquired by GCS.

 

The telescope will collimate, and once the wavefront sensor error WFE (circled above in the GCS GUI) is below ~800 nm, LUCI will proceed with executing the observations.

 

  • The first obsitem will be the source, but offset.  There is no need to background subtract for bright targets.  The second obs item will bring the mask into the FPU and take a slit image.
  • Select the Long slit tab in the RTD GUI

 

 

 

  • Confirm the auto-populated filename for alignment (source) (blank for background) in the target selection section are correct, then “Single img…”.
  • In the Aladdin display, click on your source. You can zoom and click multiple times to get reasonably close to centered on your target. Use the Finding Chart provided by the PI to ensure you select the correct source.
  • Click “Set1” then center target position(s) to centroid on your source.  Confirm the red ‘+’ is in a believable position.
  • From the slit image, determine the position in the slit where you would like to center your object:
    1. Still in the Long slit tab of the RTD GUI, Confirm the auto-populated filename in the slit selection section is correct, then click “USE”.
    2. In the Aladin display, click on your slit. You can zoom and click multiple times to get reasonably close to centered on your target.
    3. If you want your source centered somewhere other than Y=1024, uncheck the Use fixed Slit1 Y position box or change the Y coordinate where it will center your source.
    4. Click set then center slit position to centroid on your slit

 

  • Calculate the offset from source to slit and send that offset to the telescope. To do this click “Calculate” in the Long slit tab. Confirm that the offsets make sense, then send if they do. This will insert an offset ObsItem into the queue.
  •  Click “GO!” on the Observation Execution GUI. This will execute the alignment offset, take the source+slit image and then pause the queue.
  • If you are happy with the source alignment on the slit, click “GO!” again to start executing the spectroscopic portion of the script. If not, you may manually execute a small offset on the Telescope Service GUI and take another image to confirm your source position in the slit.  Manually take the other image using the RMGUI.
  • Once acquired, the science portion of the script will run.

The LS_2.0_1.5_arcsec Mask

When aligning observations for the LS_2.0_1.5arcsec mask, the nominal center pixel positions are: 

1.5″: Center on Y=580 
2.0″: Center on Y=1468

Two Target Acquisition

Two target acquisition follows the same basic pattern as bright or faint star acquisition (depending on the brightness of your sources, but with a few important differences.
Follow the instructions above until the image, or sky subtracted image, of your targets is displayed. Then:
  1. Click on the Target(s) drop down menu and select ‘2’
  2. In the Aladdin display, click on your lower source, the one closest to the bottom of the image. You can zoom and click multiple times to get reasonably close to centered on your target. Use the Finding Chart provided by the PI to ensure you select the correct source.
  3. Click “Set1” then center target position to centroid on your source.  Confirm the red ‘+’ is in a believable position.
  4. In the Aladdin display, click on your upper source, the one closest to the top of the image.
  5. Click “Set2 then center target position to centroid on your source.  Confirm the red ‘+’ is in a believable position.
  6. The mask will then be brought into the FPU and an image of the slit taken. Determine the position in the slit where you would like to center your object:
    1. Still in the Long slit tab of the RTD GUI, Confirm the auto-populated filename in the slit selection section is correct, then click “Use” .
    2. The “Use Fixed Slit1 Y position” checkbox is ignored for two target acquisition. You do not need to change it.
    3. In the Aladin display, click on the position on your slit where you want your lower target to be placed. You can zoom and click multiple times to get reasonably close to centered on your target.
    4. Click ‘set; to automatically fill the ‘Slit1’ X and Y positions. The ‘Slit2’ X and Y boxes will also be filled. The Y position of ‘Slit2’ is automatically set by adding the Y position of ‘Slit1’ to the the difference in Y position between ‘Target1’ and ‘Target2’. You only need to click once!
    5. Click “Center Slit Position” to centroid on your slit. The ‘Slit1’ and ‘Slit2’ positions will be automatically updated.
  7. Calculate the offset from source to slit and send that offset to the telescope. To do this click “Calculate” in the Long slit tab. Confirm that the offsets make sense, then send if they do. This will insert an offset ObsItem into the queue.
  8. Click “GO!” on the Observation Execution GUI. This will execute the alignment offset, take the source+slit image and then pause the queue.
  9. If you are happy with the source alignment on the slit, click “GO!”  again to start executing the spectroscopic portion of the script. If not, you may manually execute a small offset on the Telescope Service GUI and take another image to confirm your source position in the slit.  Manually take the other image using the RMGUI.
  10. Once acquired, the science portion of the script will run.  

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