Monday, August 13, 2012

Orion Parsec KAF8300 CCD Linearity Test

The main camera of the VAO is an Orion Parsec that has a KAF8300 CCD.  One of the issues with this camera is the possibility of non-linearity as it fills the pixel electron well.   The KAF8300 uses Anti-Blooming circuitry to drain current as the pixels fill up.   This has the desirable effect of eliminating blooming from bright stars in your image while increasing your dynamic range.   The downside of this technology is that it lowers the quantum efficiency of the CCD since there is additional electronics in each pixel to drain the current out.   More importantly, it adversely affects photometric measurements as the pixel fills up.  The measurements at higher ADU counts will show non-linear response.   Therefore, in an attempt to quantify these deviations from linearity for my camera, I have performed a linear test.   The test is simple enough.  Take flat exposures of increasing time steps and plot the counts vs time as you can see from the plot I present here.   Notice that the asymptotic error of the linear fit is of the order of 0.39% or about +/- 12 ADU. 

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