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              the pros and cons of "classical" photometry

photo-electric photometry
          CCD photometry           
  • used extensively for high-speed work in the 1970s and 1980s
  • photon-counting: zero readout time and noise
  • sky background and comparison stars require multiple channels
  • poor QE: 25% at peak and only a few per cent in the red
  • one band only
  • requires fixed and typically large apertures
  • started in 1970s
  • simultaneous measurement of sky and comparison stars
  • high QE: up to 95% over wide wavelength range
  • readout noise and slow readout time
  • one band only