Alignment

System Pupil Alignment

Tweeter Pupil Alignment (F-Test)

To align the pupil on the tweeter, we perform the F-Test (which is actually an R).

Prepare the system as in Daily Startup, then configure:

  • fwpupil to open (in Coronagraph Alignment GUI)

  • fwfpm to open

  • fwlyot to open

  • fwscind to pupil (in camsci1Ctrl)

  • fwsci1 to z (in almost all cases you should align in z for repeatability)

  • configure camsci1 so that you can see the pupil without saturating.

  • Move stagesci1 to preset fpm.

Now put the test pattern on the tweeter with Pupil Alignment GUI for dmtweeter. Press the set test under Tweeter

Next, use the “TTM Pupil” section to align the pupil on the tweeter using the arrow keypad. The following figure demonstrates what a good alignment looks like.

../_images/f-test-good.png

When done, use the Tweeter zero test button on the Alignment GUI.

NCPC Pupil Alignment (J-Test)

To align the pupil on the NCPC DM, we perform the J-Test.

The system should be configured for the F-test above. Next,

  • Move stagesci1 to preset jtest.

  • Put the test pattern on the NCPC with the “Set Test” button next to “NCPC” on the Pupil Alignment GUI.

  • Press the set test under NCPC

Next, use the “TTM Peri” section to align the pupil on the tweeter using the arrow keypad. The following figure demonstrates what a good alignment looks like.

  • Clear the J-test with the “clear test” button on the Pupil Alignment GUI

  • Return stagesci1 to the fpm position

Pyramid Alignment

  • In the Alignment GUI, Tip Alignment should show “move woofer” above the directional buttons. Use the directional buttons to try and get all four pyramid pupils uniformly illuminated.

  • Using the directional buttons under the “Pupil Fitting” section to move the pupil images on camwfs until the “Avg:” x and y displacements are less than 0.1 pixel.

Warning

The “pupil tracking loop” is not used in lab mode, only on-sky.

Close loop and refine pupil alignment

If CACAO is not yet started, consult the CACAO startup guide.

In the holoop control GUI:

  1. zero all gains

  2. set global gain to 1

  3. apply a small nonzero gain to tip and tilt

  4. close the loop

Close a number of tweeter modes > number of offloaded modes, then turn on t2w offload in the offloading GUI.

Work your way up the mode blocks in the loop control GUI. As you close more modes, return to the directional buttons under the “Pupil Fitting” section of the Alignment GUI and try to keep the displacements under 0.1 pixel.

Coronagraph Alignment

From the camsci1 gui, set

  • fwscind to pupil

  • stagesci1 to telsim

With the camsci1 shutter open, take a new dark. This will serve as the reference for alignment.

In the coronagraph alignment GUI: set fwpupil to bump-mask.

The camsci1 viewer will show the difference image, making it easier to align with the (now obscured) spider arms of the pupil.

Use the “Pupil Plane” directional buttons on the coronagraph alignment GUI to align the mask to the pupil.

../_images/bump_mask_alignment.png

Once the bump mask is aligned, remember to close the shutter on camsci1 and take a new dark.

Continue improving PSF quality with :doc:`../software/fdpr`