There are 2 ways to remove coma by moving the AdSec hexapod:
  1. using the ARGOS terminal
  2. using TCS GUI

How to remove coma using the ARGOS terminal

  1. Open an ARGOS terminal and type:
from argos.arbitrator.tcs.hexapod_controller import Coma
correction= Coma.fromNumPyArray(np.array([xxx, yyy]))
argos.arbitrator.correctHexapodComa(correction)

Remember that xxx and yyy corrections are expressed in micrometers of wavefront rms. You need to use the format x.x and y.y (e.g. [1.0, 1.0]), otherwise it will give an error.

How to remove coma using the TCS GUI

  1. Login on obs[x] as LBTO. See UsefulLoginInfo
  2. Start OSSGUI right (or left)
  3. Click on the icon of the M2 (right or left) to open the hexapod command window
  4. Write down the 6 numbers in the Absolute position line: this is where you need to move back in case you get lost
  5. Write zero in the 6 fields of Move Relative line.
  6. To correct for 1um of coma surface rms along X write X=+0.982mm and RY=+102". Click on Set Reference and then on Move Relative.
  7. To correct for 1um of coma surface rms along Y write Y=-0.982mm and RX=+102". Click on Set Reference and then on Move Relative.
Always click on Set Reference first and then on Move Relative

NOTE: Alternatively, coma may be removed by using the "Zernike Coefficients" section of the PSF GUI. The coma coefficients are 7 and 8.
  1. Select the desired coefficient by clicking "Prev" or "Next".
  2. Click "Clear coefficients".
  3. Enter a value (it is relative). The value can be hundred or tenth. It requires to watch the PSF to get a feedback of the corrections.
  4. Click "Send".
  5. Click "Adjust miror" and check that the "Hexapod Platform Positions" change accordingly (x, y , RX and RY).
Acquire_coma_020921_2.png

-- LorenzoBusoni - 04 Nov 2014
Topic revision: r9 - 03 Sep 2021, JuanCarlosGuerra
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