Science Operations

Mixed Mode: LBC+LUCI/MODS

Contents

  1. Script Preparation
    1. Copointing Limit
    2. LBC script modifications
      1. Add \<SYNCOFFSET\> line to indicate ‘asynchronous’ LBC offsets
      2. LBC script with dec=-90
    3. No MODS or LUCI script mods needed
    4. Summary of scripts needed
  2. Execution
    1. LBC+MODS
      1. Re-entering MODS scripts
    2. LBC+LUCI

Script Preparation

Monocular LBC and MODS/LUCI scripts should be prepared as usual, however with the important constraints that:

  1. the coordinates and position angle for both sides (LBC and MODS/LUCI) are exactly identical; and
  2. that any dithers be kept small enough that there will never be a time when the copointing limit will be exceeded.

Copointing limit

In binocular observations, pointing/offsetting is achieved in two ways: through the mount and through the mirrors. “Synchronous” presets and offsets are slews and dithers done only through moving the mount. Both sides, SX and DX, move together to the same coordinates. “Asynchronous” presets and offsets are slews and dithers done through moving the mirrors of one or the other side only. These are constrained by the limits of travel of the mirrors. “Asynchronous” offsets must be small enough that they remain within a circle with radius 50″ and center at the mount position. “Asynchronous” offsets on both sides can, in the extreme case, result in the two sides pointing 100″ apart, but never 100″ from the mount position.

The diagram below, from Rothberg et al 2018, may help explain the copointing constraint.

In the absence of a true binocular planner, much care must be taken not to exceed the copointing constraints.

LBC script modifications

Add <SYNCOFFSET> line to indicate “asynchronous” LBC offsets:

By default, LBC sends both synchronous presets and offsets. A line needs to be added to the LBC script, after it has been generated, to allow LBC to send asynchronous offsets. This line is enclosed by the xml tags <SYNCOFFSET> and </SYNCOFFSET> and contains a list of comma-separated 0’s, one for each offset. The 0 indicates that the offset will be an asynchronous offset (1 would indicate a synchronous offset but, since that is the default, there is no need to add this line unless asynchronous offsets are desired).

LBC script with dec=-90:

At least two LBC scripts will be needed: one which sends a preset and one which does not.

  1. Initial script: The one that is generated & has the line added to indicate “asynchronous” offsets.
  2. Repeat script: A copy of that one but with the declination set to -90 degrees, to indicate that it should not send a preset. It will still dither, and the dither pattern can be changed to differ from the pattern used in the initial script.

No MODS/LUCI script mods needed

No modifications to the MODS or LUCI scripts are needed. Just generate monocular scripts as usual: both the acquisition and observation scripts for MODS; and the paired acquisition+observation script for LUCI.

Summary of scripts needed

3 LBC and 2 MODS (acquisition and observation) or 1 LUCI (acquisition+observation pair) scripts are needed to run a mixed-mode LBC + MODS/LUCI observation.

  • LBC “pointing” and first collimation
  • LBC initial OB (with correct coordinates)
  • LBC repeat OB (with dec = -90)
  • MODS:
    • acquisition
    • observation
  • LUCI:
    • paired acquisition + observation script

Execution

The sequences here assume LBC Red and either MODS1 or LUCI1 for simplicity.

LBC+MODS

  • Authorize the telescope as NONE + LBCR
    • Send the “copointing” (in this case pointing) script.
    • Stop it before taking data
    • dohybrid, /redonly, (/x2) (or dofpia, /redonly, {/x2} if this is not the first LBC collimation of the night or after clearing active optics)
    • After collimation is done, run the “copointing” script to take an image
    • LBTtools.camera = “REDLBC”
    • Load the LBC package
    • ptautoadjust <hhmmss> (where hhmmss is the timestamp of the image taken)
      • Position the cursor on the star and hit Enter to correct the pointing
  • Authorize the telescope as MODS + LBCR pseudomonocular
    • In this mode, the OSA can correct pointing and collimate MODS-SX.
    • You may run dofpia, /redonly to collimate LBCR again, but it not guaranteed that there will be many pupils in the collimation region.
    • If MODS-SX collimation takes a long time, then in the next step, the observer may want to send the LBC OB just to slew, but then to tweak up focus/collimation; in this case they will need to use the LBC  “repeat” OB to take science data.
  • Authorize the telescope as MODS + LBCR binocular
    • acqMODS –mods1 –bino myscript.acq
      • Acquire the target(s) on the slit or in the mask
    • Play the LBCR OB. This can be started while acquiring the target with MODS.
      • If it has been a while (~10 min) since LBCR was last collimated, then you may wish to stop the LBCR OB, run dofpia, /redonly to tweak up the collimation, then run the LBCR “repeat” OB (it will not send a preset) to take science data.
    • execMODS –mods1 –bino myscript.obs to take MODS data once the slit/mask alignment has been done.

The LBC side will have to be refocused/recollimated every ~30 minutes. As long as the LBC scripts that are run to refocus/recollimate and continue data-taking afterwards do not have a preset (have dec = -90), then all should be fine. This means that refocus/recollimation must be done on the field, using whatever stars are in the collimation region.

To refocus/recollimate and then continue taking LBC data:

  • dofpia, redonly, (/x2)
  • Play the “repeat” LBC OB as described above (dec = -90 and dithers indicated to be asynchronous).

Re-entering MODS scripts

Note that the MODS scripts are re-entrant, and so, if necessary, the acquisition script can be repeated to skip the preset and to configure the instrument only (-i) or to take the acquisition images only (-a). See the MODS Script Engines page for more information on options for MODS acquisition scripts and observation scripts (or just type acqMODS or execMODS followed by a carriage return).

LBC+LUCI

  • Authorize the telescope as NONE + LBCR
    • Send the “copointing” (in this case just pointing) script.
    • Stop it before taking data
    • dohybrid, /redonly, (/x2) (or dofpia, /redonly if this is not the first LBC collimation)
    • Run the “copointing” script to take an image
    • LBTtools.camera = “RedLBC”
    • Load the LBC package
    • ptautoadjust <hhmmss> (where hhmmss is the timestamp of the image taken)
    • Position the cursor on the star and hit Enter to correct the pointing
  • Authorize the telescope as LUCI + LBCR
    • Load and run the LUCI acquisition + observation script
      • Acquire the target(s) on the slit or in the mask
    • Play the LBCR OB. This can be started while acquiring the target in the LUCI slit/mask.