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CGS4 flat fields

Suggested Flat Exposure Times

40 l/mm grating:

Wavelength Order BB Aperture Exposure Tim (secs)
1.15 2 5.0 2.0
1.30 2 5.0 2.0
1.70 1 1.3 0.6
2.20 1 1.3 0.25
3.10 1 3.2 0.75
3.80 1 2.0 2.0
4.90 1 1.3 1.0

150 l/mm grating:

Wavelength Order BB Aperture Exposure Time (secs)
1.15 3 5.0 5.0
1.30 3 5.0 2.5
1.70 2 2.0 1.0
2.20 2 3.2 0.25
2.20 1 3.2 0.12

Echelle:

Because of the extremely small wavelength coverage of the echelle, it is fairly impracticable to provide a table of suggested blackbody apertures and exposure times. The quickets way to determine an appropriate exposure time and aperture is as follows (this technique can be used with any grating):
  1. Write an astronomical config for the wavelength you wish to observe at.
  2. Set to this config using the Set_Single_Observation menu in the CGS4 software and specify a flat observation.
  3. Select "Movie", select an exposure time in "Set_Movie" (e.g., 0.5 secs) and then "Run_Movie"
  4. Note the counts on the movie screen.
  5. Select "Direct_Motor_Control" and select another blackbody aperture. You will see the counts change.
  6. When you are happy with your selection (i.e., 3000 - 4000 counts) abort the movie and edit your config with the appropriate numbers.
Contact: Tom Kerr. Updated: Wed Oct 6 11:54:01 HST 2004

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