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Alignment Observing

Observations to check whether AOS is putting science array in the right position, and to map response of PSF patterns to errors in hexapod degrees of freedom

All be done in i band.

All exposures 25s (or 30 is ok also if you want to see whether guider locks on, but guiding is not needed)

  1. Choose the best focus known to us and take 2 25-sec exposures
  2. Take a traditional focus frame (multiple shutter openings but just one readout) with 9 exposures at 25 um z intervals centered on best focus, 10-20s each.
  3. move hexapod z by -100, -50, 50, 100 microns relative the best focus position. At each position, take 2x25s exposures.
  4. move back to the best focus position.
  5. move hexapod x by -500, -250, 250, 500 microns relative the best focus position. At each position, take 2 exposures.
  6. move back to the best focus position
  7. move hexapod y by -500, -250, 250, 500 microns relative the best focus position. At each position, take 2 exposures.
  8. move back to the best focus position and take 2 25-sec exposures
  9. move hexapod xtilt by -40, -20, 20, 40 arcsecs relative the best focus position. At each position, take 2 exposures.
  10. move back to the best focus position
  11. move hexapod ytilt by -40, -20, 20, 40 arcsecs relative the best focus position. At each position, take 2 exposures.

Instructions for setting hexapod positions

  1. Establish best focus by ensuring that the AOS has reach a stable focus. See the donut telemetry page.
  2. Turn the Tweak from ACC to NONE (this turns the active focus adjustment from Donuts Off).
  3. Uncheck the Telescope LUT
  4. Record the current hexapod settings, for use as the nominal hexapod setting.
  5. all other normal operating settings are OK
  6. Input the hexapod values into the Hexapod window in the observer console. Please be sure to use the current hexapod values + best focus for the other degrees of freedom, ie. besides the degree of freedom being changed.
  7. Lastly if the whole procedure takes too long such that the telescope moves to more than 10 degrees from Zenith, I suggest moving back to Zenith when reestabilishing best focus.