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 http://www.youtube.com/watch?v=wSiFoG8qgKI 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:
- 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
- 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)
- 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.
- 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
- 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
- Finally, we have an optimized closed loop. The instrument can be turned over to the astronomer for diffraction-limited data acquisition