Nonlinearity in the Detector used in HDS

The nonlinearity of the EEV 42-80 CCDs used in HDS has been investigated by Tajitsu et al. 2010.
While good linearity is confirmed in the data recorded for electron numbers less than 10,000e-(~6,000ADU), significant nonlinearity appears for higher electron numbers. The nonlinearity effect is of the order of several percent at 50,000e-. No clear pixel-to-pixel difference is observed in the nonlinearity effect in a given chip; however, thereis a notable difference in the nonlinearity effxt between two CCD chips used in the instrument. No siginificant time variation in the nonlinearity effect is found from our measurement up to now (June 2010).

• An IRAF CL-script for CCD non-linearity correction (updated 9/23/2011).
  
  This script should be adopted to each frame after over-scan correction.
  Please use this script only for HDS frames with the Messia-V CCD controller system (after March 2004).
  
  
• When referring to this nonlinearity correction in a paper, please use the follwing citation.
  
  Tajitsu et al. 2010, Nonlinearity in the Detector used in the Subaru Telescope High Dispersion Spectrograph,
  Publ. of National Astronomical Observatory of Japan, 13, 1