Science Operations

Scripting Basics

Observing with the one or both Large Binocular Cameras at the Large Binocular Telescope requires scripts that co-point and collimate the telescopes, and then configure and execute a sequence of observations of the science target. All scripts (or Observing Blocks, OBs) for LBC are in xml format and can be produced using the LBT Observing Tool (OT). The Observing Block Creation GUI provided by the LBC team also remains available but the OT is strongly preferred.

For each target, you should include:

  • A co-pointing OB (yourCopoint.ob)
  • A finding chart of the co-pointing target, with target clearly identified – Required
  • Science OB/s (yourScience.ob)
  • A finding chart of your science field – Optional

Detailed instructions on producing valid copointing OBs that can be used for both collimation and copointing are detailed below.

Science OBs

Science OBs should be 30-40 minutes in length, after which time the telescopes will need to be collimated again. Instructions for using the OT to create your OBs are available here, along with a library of example and template observations and calibrations.

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.

Co-pointing OBs

Since LBC operates in a fully binocular sense it is critical to minimize the demands on the guide loop by making sure the mount correctly knows where it is pointing and ensuring the two sides are co-pointed. This is be achieved with a co-pointing OB, at or near your science target field.

Select an easily identifiable (isolated, 12.8 < R < 14.5) source with proper motion corrected coordinates as the “co-point” target that you preset to in the co-point OB. This can be your science target itself if it meets the requirements, or a star in the same field, or if your science target is significantly extended it could be a nearby field. Almost any star in the USNO-B1.0 catalog would do. Provide a finding chart as well so that identification of the correct source is assured. Because the coordinate reference source is relatively bright, only a short exposure is needed for the pointing correction.

The co-pointing target is also used for collimation, and very crowded (i.e. Galactic plane) fields can be problematic for the collimation script (dohybrid/dofpia) as the out-of-focus pupils overlap. Select your fields carefully.

Prepare yourCoPoint.ob with the following parameters:
  • Choose a target that meets the following criteria:
    • Known, proper-motion corrected, coordinates
    • Unresolved point source (stars)
    • Field is uncrowded (not much contamination from overlapping pupils)
    • Field is 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
  • 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
  • Make a finding chart (7.5’x7.5′ from DSS is fine) identifying the source

Mixed Mode OB

For mixed mode OBs please see: Mixed Mode LBC + LUCI/MODS

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.