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IMACS filter focus procedure


To update the focus offset for a given filter, do the following:

  1. Start IMACS from observer workstation
  2. Load filter in desired filter server and update the table in IMACS setuptool.
  3. Install the New Pinhole mask in the mask server and update the masks table in IMACS setuptool.
  4. Start ffs gui on observer workstation, put ffs to IN position and start low lamps (Ql).
  5. Open mirror covers, turn off lights in dome and close louvers
  6. First test the R filter: Move to R filter, set subraster to f4_focus.sub or f2_focus.sub, take exposure at nominal focus then turn off the focus control and offset in steps of +/- 20 focus units to find the minimum at the present temperature. Measure the fwhm of the center pinhole in the subraster at each focus position and determine the minimum. If different from the nominal, update the value in the filter focus section of the IMACS setuptool and note the current temperature.
  7. Now repeat for new filter and input the value for the focus difference between the new filter and the R filter.
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