ISPI Noise & noise patterns

A simple receipe to measure the noise:

  1. Collect 10 darks at shortest exposure (3.227s)
     
  2. Subtract last 3-4 pairs from each other
    Dark10-Dark9, Dark9-Dark8, etc
     
  3. imstat with lo=-100 hi=100, to get rid of outlayers
     
  4. Divide average std number by sqrt(2) and multiply by 4.25e-/ADU (gain)

    • If number is less than 20e-rms, the noise is within specs.
    • If the number is more than 20e-rms, ask moutain support to

      • check that the cables and ground strap are well-tighed and perhaps ask them to move the cables.
      • Switching the motors for the filterwheels OFF & ON might help too.
  1. Measure the noise again, and again...

 

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February 21,2007