Script Preparation

For binocular LBCB+LBCR and monocular LBCB/R observations, two types of scripts are needed:

1. a Copointing script
2. a Science script(s)

For mixed-mode LBC + MODS/LUCI observations, an additional script is needed. See Mixed Mode: LBC+LUCI/MODS for details.

All scripts for LBC are in xml format and can be produced using the LBT Observing Tool (OT). Please see the pages under Script Preparation for a guide to using the OT to prepare LBC scripts. What follows here is just a brief explanation of the scripts and materials needed.

Copointing Script

• The copointing script is used both to (1) collimate and (2) correct the pointing and the copointing of both sides of the telescope, while also maximizing the available range of the optics so that both collimation and copointing can be maintained throughout the observation without a mirror being driven into a limit. The importance of pointing and copointing is explained here.
• The copointing target should meet the following criteria:
  • The co-pointing target itself:
    • should be near the science target. However, collimation can be slow and imprecise at low elevation where the natural seeing is worse, so in that case, it would be advantageous to identify a second copointing/collimation field that will be at high elevation (~65-75 deg). Collimate there and allow TMS to hold collimation as you slew to the copointing star to correct pointing/copointing near your science target.
    • should have known, proper-motion corrected, coordinates (i.e. a star from the UCAC catalog)
    • should be an unresolved point source (stars)
  • and the collimation region below the pointing center:
    • should contains 5-6 stars with 15<R<16.5;
    • but not be too crowded (otherwise the extra-focal pupils will overlap)
    • should be free of significant background gradients (large galaxies, nebulosity)
  • Example of a bad field for DOFPIA would be a large galaxy like M51 (like this)
    or a Globular Cluster
• The LBC OT library contains examples and templates for the co-pointing observation. The parameters are:
  • Read full CHIP2 ccd, the others are not needed
  • 1.0 sec exposure
  • Use r-SLOAN (LBC-Red) and V-BESSEL (LBC-Blue), same as dofpia
• A finding chart which indicates the copointing target is essential. A screenshot of chip2 from the target position editor in the OT would suffice.

Science Script(s)

• Science scripts:
  • command dithers and filter/exposure time changes. The outer loop is over dithers and the inner loop over filter and exposure time changes. The OT template, “Each Filter at Each Dither” is set up for this.
    • offset1 dRA dDEC
      • filter1, exptime1_filt1
      • filter1, exptime2_filt1
      • filter2, exptime1_filt2
      • filter1, exptime3_filt1
    • offset2 dRA dDEC
      • filter1, exptime1_filt1
      • filter1, exptime2_filt1
      • filter2, exptime1_filt2
      • filter1, exptime3_filt1
    • offset3 dRA dDEC
      • …
  • If you want to complete the dither before changing filters, there is an OT template for that and it will generate a set of scripts, <myscript>_#.xml, one for each filter.
• should be ~40-min in duration, to allow for re-collimation if necessary.
• are not easily re-entrant. If, e.g., the script needs to be restarted after the 3rd dither, then a copy of the script will need to be made and edited to remove the first two offsets.
• one or more scripts can be looped over using the python script, /lbt/lbto/supportscripts/SymbioticSupport/loop_observe.py [NOTE: runs on robs and obs-32bit, but not on obs1,2. It needs to be converted to python3]. This can be useful if, for example, you want to monitor 3 fields.
• A finding chart may be helpful if you are concerned about chip gaps, or saturation of specific objects, but is not required for science observations.

About LBC offsets

When preparing an LBC script in the OT, offsets can only be entered in Absolute DET X/Y coordinates. The OT will convert these to Absolute RA/Dec offsets (required by the LBCs) in the output script according to the following conversion:

where theta is the position angle.