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General :
Observations :
Operations :

   
Procedure :
  Measure of the Convertion Factor
Author :
   SOFI team
Release :
  12/09/99 : update 
 06/01/99 : creation
 

The convertion factor (e/ADU) of SOFI is measured every month. This is done with the template SOFI_det_tec_Gain.obd . The results are stored in the file /vltdata/SPC/Sofi_det_tec_Gain.SPC on wsofi, the last MIDAS images are saved in /home2/sofi/midwork always on wsofi.

  • Make sure MIDAS for PCO is running on wsofi.
  • Make sure SUSI M4 mirror is in position SOFI.
  • Load the template SOFI_det_tec_Gain.obd from /data/SOFI/SYSTEM/COMMON/OBD/CALIB into Bob and run it. The calibration unit will be automatically moved in. You will be asked to switch the calibration lamp on, set the light intensity to have an average of about 1000 ADU in the illuminated part of the array when the DIT is 1.18 (default value for the first image). To get consistent results it is CRUCIAL  to use the  HALOGEN LAMP in the CALIBRATION UNIT.
  • The lamp will be automatically switched off at the end of the template and the calibration unit put out.
  • The value of the convertion factor in e/ADU will be displayed in the bottom part of the BOB window at the end of the template. It takes about 30 minutes to run the template with the default parameters.
  • A plot of the square of the variance versus the average ADUs will be displayed in a MIDAS graphic window, check that no point deviates significantly from a linear relation. Signal the presence of deviant points.

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