Jul 03 2010

SBIG ST-8300M Read Noise Measurement
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As discussed in a previous post (here), read or readout noise is the noise or uncertainty added to every pixel value read out of a CCD array. This noise is largely associated with the imperfect conversion of an analog signal into a digital value.

The method to determine a CCD’s readout noise contribution to the final signal is as follows1:

    1. Obtain two bias frames (0 length exposures).
    2. Add a constant offset to one of the bias frames (e.g. 500).
    3. Subtract the second bias frame from the offset bias frame.
    4. Find the standard deviation for a region of the resulting frame.
    5. Calculate Read Noise (e- RMS) = StdDev * Gain / SQRT(2)

The results of performing these operations on ten pairs of bias frames is summarized in the table below:

Pair # Std. Dev Gain Read Noise2
Bias Pair 1 35.388 ADU 0.37 e-/ADU 9.26 e- RMS
Bias Pair 2 35.305 ADU 0.37 e-/ADU 9.24 e- RMS
Bias Pair 3 35.327 ADU 0.37 e-/ADU 9.24 e- RMS
Bias Pair 4 35.294 ADU 0.37 e-/ADU 9.23 e- RMS
Bias Pair 5 35.250 ADU 0.37 e-/ADU 9.22 e- RMS
Bias Pair 6 35.259 ADU 0.37 e-/ADU 9.22 e- RMS
Bias Pair 7 35.416 ADU 0.37 e-/ADU 9.27 e- RMS
Bias Pair 8 35.372 ADU 0.37 e-/ADU 9.25 e- RMS
Bias Pair 9 35.220 ADU 0.37 e-/ADU 9.21 e- RMS
Bias Pair 10 35.226 ADU 0.37 e-/ADU 9.22 e- RMS
Average 35.306 ADU 0.37 e-/ADU 9.24 e- RMS

1From “Handbook of CCD Astronomy Second Edition” by Steve B. Howell

2Published read noise for this device = 9.3 e- RMS

 

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