Video demo: Acquiring a star and closing the loop

This video demonstrates the MagAO high-level software GUIs used to acquire the star, set up the AO system, and close the loop.  The entire process takes about ~3-4 min. at this time.

(Filmed by Alfio, narrated by Laird, cameo by Katie operating the VisAO camera)

Go to to view the video in high-def.

After the telescope slews to a new target, the guider will acquire the star to within 4” on the Technical Viewer (CCD 47 in AO acquisition mode; otherwise CCD 47 is the VisAO array).  Next, the MagAO Command GUI controls the AO system and is operated as follows:

  1. PresetVisAO — Transforms the CCD 47 from its role as the Science Camera (VisAO) to its role as the AO acquisition camera (Technical Viewer).
    • Takes control of the CCD 47, gimbal, and filter-wheel 2 and 3
    • Opens up filter-wheel 3 (coronagraph stops and SDI narrow-band filters)
    • Centers the gimbal
  2. PresetAO — Configures the board for acquisition, and uses the estimated NGS magnitude in order to determine the AO system parameters (frame rate, modulation, binning).
    • Start with a guess of the NGS mag (entered by hand, or will be read in from the starlist provided by the astronomer) — required for appropriate speed and binning to get good SNR photometry. These settings are read from a lookup table
    • Opens up filter-wheel 2 (SDSS r’, i’, z’, and 950 long-pass filters)
    • Moves gimbal to point off axis to take CCD 47 darks
    • Sets binning and framerate on both CCD 39 and CCD 47 based on the estimated NGS magnitude.
    • Places the beamsplitter wheel in the dark position for CCD 39 darks
    • Once darks are taken, re-centers the gimbal
    • Wait for all movements to finish (stages, filterwheels, etc)
  3. AcquireRef — Aligns the guide star onto the pyramid.  Metric is position of the star on the Technical Viewer (CCD 47).
    • Finds star on Technical Viewer
    • Finds offset from pre-determined home position (green cross)
    • Moves X,Y Bayside stages (entire W-unit) to remove offset
    • The above steps are performed iteratively until the star is on the green cross to within 0.2 mm of stage movement
    • Set filter-wheels for AO. Filter-wheel 1 (beam splitter) will be placed in the correct position based on star magnitude.
  4. AutoCenter — Fine-tuning of the alignment onto the tip of the pyramid.  Metric is pupil illumination on WFS camera (CCD 39).
    • Button on the CCD 39 image viewer
    • Moves X,Y Bayside stages to even out the illumination (i.e. zero out tip and tilt)
    • Iterative process; Final precision is ~few microns
  5. StartAO — Closes the loop.
    • First closes the loop with only 10 low-order modes to center up the camera lens (the camera lens loop aligns the pupil images to keep the illuminated pixels constant to 1/10th pixel)
    • You can next load artifical turbulence in the lab to simulate on-sky AO
    • Sets the frame rate, modulation, and binning determined in PresetAO
    • Closes the loop with all modes (400 modes in bin 1; 120 modes in bin 2; 50 modes in bin 3; 28 modes in bin 4) and low gain
    • AutoGain starts and iteratively guesses-and-checks the gain for each mode grouping (low, mid, and high) that minimizes the slope RMS
  6. Finally, we have an optimized closed loop. The instrument can be turned over to the astronomer for diffraction-limited data acquisition