Science Operations

Observing Procedure

The procedure for observing with the LBCs follows, for each new target, the sequence: collimate; copoint; and, finally, observe. For each target, the PI should prepare not only the science OB but a “copointing/focus” OB which should have as its target a bright, easily identifiable, star with proper motion corrected coordinates and which should contain within the region of chip 2 that is used for collimation at least ~5 bright stars. Instructions on preparing a copointing OB can be found here.

These steps are detailed in each section, below:
Collimate
Co-Point
Run Science OB

 

Two routines are run sequentially on the copoint target collimating then co-pointing:

Collimating

  • Following the directions outlined in “Executing OBs” load and run yourCoPoint.ob, but STOP the OB as soon as the telescope presets. You DO NOT want LBC to take any data yet.
  • Wait for the telescope to be in position. In the idl window:
    • For the first collimation of the night, or if active optics have been cleared, run dohybrid
    • Otherwise, run dofpia, /X2 (X2 doubles the exposure time to 32 seconds, and averages over seeing variations, but should not be used for fields near the zenith, i.e. at elevation > 85 deg). If, for some reason, you have chosen to ONLY use LBCR or LBCB, add the flag /RedOnly or /BlueOnly.
  • The procedures, dofpia and dohybrid loop over these steps until the aberrations measured are within the convergence criteria:
    1. take a pair of extra-focal pupil images,
    2. analyze them to determine the aberrations present, and
    3. command the mirror to move.
  • Collimation can be tricky when there is a large temperature differential across the mirror or between the mirror & air. dofpia/dohybrid have problems with fitting high order spherical. To turn it off, use dofpia in interactive mode; the response “z22” will negate the z22 correction.
  • All of the keywords for dofpia are listed below. The syntax for their use is: dofpia, /keyword
    • /x2
    • /blueonly or /redonly
    • /askme

Co-Pointing

The copointing procedure adjusts the pointing model and the primary mirror to position the target as close as possible to the rotator center on each LBC while maintaining collimation and maximizing the range of travel available to the primary mirrors as they move according to a temperature and elevation dependent collimation look up table. This last goal explains the name of the LBTtools task that is used to copoint and range-balance, lbcrangebal.

lbcrangebal takes as input the pair of images generated by your copointing OB, yourCoint.ob

Prepare by loading the Observe package under LBTtools.
    1. In your IRAF session load Observe
    2. cl> unlearn lbcrangebal
  1. Once dofpia has completed and converged, run yourCoPoint.ob, this time allowing it to complete and take the in-focus images
  2. epar lbcrangebal and enter the timestamp number from the filenames for the red and blue images taken by the yourCoPoint.ob script
  3. run lbcrangebal on these images; follow the direction in IRAF; This corrects pointing (IE and CA) and co-pointing (SX, DX M1s). 

If you are running only LBC Blue or LBC Red, then you can still correct the pointing using the task, ptautoadjust which is in the LBTtools.LBC package.

  1. Set the Specify REDLBC or BLUELBC in the CAMERA parameter in LBTtools
  2. After Loading LBTtools
  3. load LBC
  4. use  ptautoadjust to adjust the pointing only on one side

Note that lbcrangebal will display the LBC images to the last ds9 window opened. On robs, if you opened modsDisp after RB_Science, your copointing images will go to modsDisp. See Troubleshooting for more about ds9-IRAF interactions.

You are ready to observe!

Run Science OB

  • Upload the OB by (2) clicking the downward pointing arrow. The OB name and basic information will appear to the right.
  • Play the OB using the (3) right-pointing arrow
  • Confirm that the data are displayed correctly in RB_Science.

 

Stopping an OB: Pressing the stop button will interrupt the current exposure or readout and will NOT save it. Pressing play will resume the OB, and retake this exposure. Importing the OB again before pressing play will start the OB from the beginning.

Pausing an OB: Pressing the pause button will cause the OB to pause after the current exposure finishes. This exposure will be written to disk. When you resume the OB, the next exposure in the sequence will be taken. The exposure time scaling can be adjusted when the OB is paused; this may be helpful when taking flat fields.

A useful tool when observing multiple scripts at the same location is to loop the scripts together using the python script loop_observe.py located in the /home/lbcobs/supportscripts/SymbioticSupport/ directory on the obs machines. This script is intended for running multiple LBC OBs repeatedly.  To use type:

./loop_observe.py -o 'my1.ob my2.ob my3.ob' -m <n_loop>

For each OB name in the obname list this script will load and play the OB, then wait for the OB to finish using the OB Progress, repeating through the obname list n_loop times (with a default of 100). One can stop the script anytime with a ^C without hurting the running OB. Loop_observe does not keep track of telescope on-source (although playing the OB does that) nor does it do anything about active optics with DOFPIA.

Mixed MODE Observing

For execution of Mixed Mode OB’s, please see: Mixed MODE LBC + LUCI/MODS Execution