Charge-shuffling for sky-subtraction

• Slits? - limited by irregularity of slits and flatfielding

• Beamswitch approach? - nod telescope object-sky

  • Object/Sky observed through exactly the same slits+pixels
  • But need 15-30 min exposures to beat down CCD READNOISE
  • Sky changes in this time ? A-B ? 0

• Sequence charge-shuffling with telescope-nodding?? Rapid sampling (~secs) (Cuillandre et al. 1994 on NTT)

  • ? A-B = 0

• Charge-shuffling developed at AAO for TAURUS

  • Joss Hawthorn, John Barton, Lew Waller, Tony Farrell

• The sky is complex+variable in the red and near-IR

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