6: MOS Tellurics

• Observation Element: Change the Observation Name in the Acquisition and Science Observation from the generic template name to something descriptive.  This can help observers easily identify observations in the OT Science Program if multiple observations are provided, and will help with script generation.
  
• Observing Condition Element: Complete the information in the Observation Conditions Element by selecting the nodes that roughly align with what was requested in your TAC proposal.  These can likely be copied directly from the associated science program assuming the desired conditions match.
  To do this, with the Observing Conditions Element selected, select COPY in the Main Toolbar. Select the Observation Element of the complimentary LUCI observation and select PASTE from the Main Toolbar.  Copy and paste the Observing Conditions Element between the Acquisition and Science Observations for consistency.

• LUCI Instrument Element: Skip the Target Element for just a moment.  The Instrument Element will define the initial configuration of the instrument, including the mask used. Configuring this first can help with visualization during Guide Star Selection.

  The LUCI Instrument Elements in the OT have many configurable components, included mechanisms and detector settings.  There are slight differences between LUCI1 and LUCI2 cameras, gratings, and permanent masks that may prevent twinning.  See the LUCI User’s Manual for a full description of available mechanisms and modes for both LUCI1 and LUCI2.

  

  Adjust the filter, (possibly the camera and grating if defaults are not desired), DIT, NDIT, Nexp, save mode, read mode to desired values of the initial observation.  Tellurics are assumed to be brighter than ~10.5 mag requiring a crossed filter combination.  The standard combinations are:

  Filter Wheel 1	Filter Wheel 2	Extinction [mag]
  P_gamma	J	0.8
  HeI	J	2.35
  OH_1060	z	3.9
  HeI	z	7

  Note that for acquisitions, the mask position will always start as “Mask in Turnout” so that the Sky and Source Images can be taken first, and for Science the mask is set to “Mask to FPU”. DO NOT CHANGE THE MASK POSITIONS.

  MOS Telluric should be “Yes”, this will prevent target information from being over written when the LMS file is uploaded.  Upload the LMS for the Mask.  Click on “—Select Masks—“.  If the mask has not been previously loaded in the science program and selecting your LMS file, load the LMS File for the Custom mask by clicking the Load LMS File from the drop down menu.  Otherwise the mask will appear in the dropdown menu, just select it.

  

  or

  
  Fill in the LUCI Instrument Element for both the Acquisition and Science Observation.

• Target Element: Enter Target. One can enter a valid SIMBAD Target Name and hit enter. If recognized, the coordinate field, magnitudes, and proper motion will populate. A list of suitable A0V or G0V Telluric candidates is provided in the Library, listed by Hipparcos Number which is a recognized designation.  Or one can manually type in the Target Name, Coordinates, Brightnesses, and Proper Motion. In the Target Element the user can adjust the Position Angle of the observation.

  At this time only seeing limited spectroscopy is available.  Check that the telescope mode is left as Active for seeing limited observations.

  
• Obtain a Guide Star.   When selecting your guide star, be mindful that large offsets are often performed during MOS telluric observations to place the star in various slits.  Select a star that can cover a wide range of positions.  Selecting a star can be done 2 ways.
  1. With Target Element: Select New in the Target Element. In the drop down menu, select LUCIGS to create a new guide star element in the Target Environment. You will need to manually enter a valid SIMBAD designation or the RA DEC for the Guide star. This is a useful option is the guide star is previously known.
     
  2. With Position Editor: Click “Manual GS” Button  on the right of the Target Element.  This will bring up the Position Element with  a popup. In the popup, select Guide Star Type LUCIGS to select a Guide Star.   You can select either the NOMAD or UCAC4 catalog for your Guide Star options.
     

     Once you select ok, the catalog will be queried and the catalog stars will be highlighted in the Position Editor (green for NOMAD and turquoise for UCAC4). Select the +LUCIGS option on the Left Sidebar then click on guide stars that fall within your Guide Probe FOV (overlay outline green). You will see an overlay of the physical probe footprint appear over the selected guide stars.  This will allow you to see any vignetted area.  You may find it better/necessary to reorient to obtain a suitable guide star.

     

     The selected stars will populate in the Target Element.

     

  COPY and paste the Target Element between the Acquisition and Science Observations for consistency. To do this, with the Observing Conditions Element selected in the Acquisition Observation select COPY in the Main Toolbar. Select the Observation Element of the complimentary Science LUCI observation and select PASTE from the Main Toolbar. If performing a blind offset, you may wish to put the actual target in the science observation, rather than the original offset position used in the acquisition.

• Sequence Element:

1. Acquisition Sequence:
   In the first Iterator sequence is comprised of an Offset Iterator and Object Iterator. In the Offset Iterator, “Det X/Y” Table Coordinates and “Absolute” Table Motion should be selected. Confirm this. DO NOT CHANGE. Click the “Telluric MOS” button.
   

   This will bring up a Pattern Offset Pop-up specific to the loaded MOS mask.  In the pop-up, check Acquisition and select the slit you wish to acquire on. When you click “Create”, the first offset will be calculated.

   

   Create will generate an absolute offset in the Offset Iterator to the desired slit.  The offset will appear in the offset iterator in bold and italicized.  This format indicates that the offset will be absorbed by the telescope.

   

   
   The second Iterator Sequence is comprised of a Sequence Iterator, Offset Iterator, and Object Iterator.  Adjust the filters in the Sequence Iterator.  Be consistent with selections made in the instrument iterator.

   

   The second Offset Iterator should not be changed.  This second iterator sequence takes the mask image and confirmation image.
   
   For Acquisition Observations the Observe Type will always be set to LUCI Object, Class Telluric Acquisition.

2. Science Sequence: In the Offset Iterator, “Det X/Y” Table Coordinates and “Absolute” Table Motion should be selected. Confirm this. DO NOT CHANGE.  The offset iterator should contain no offsets.  Any offsets that it does have will be over written with the following process.  In the Offset Iterator, push the “Telluric MOS” button.

   In the pop-up window, this time check science and select the corresponding Acquisition observation. Select all the slits you wish to observe the Telluric through. The defaults are the left- and right-most slits, but you can observe through any slits you wish. Be sure to keep an eye on guide star availability which may affect your choice of slits.

   

   
   Select whether you want single observations at the center of each slit (A) or if you wish to dither along the slit (AB). Click “create” and the offset pattern is calculated.

   

   
   Note the first offset is greyed out. This is not a true offset, it is merely indicative that this observation is to be taken at an already offset position from the Acquisition Sequence.

   The Observe Type in the Sequence is set to Telluric.

   

Generate the script. Script generation is discussed here.