Some known CCD3-controller features

• Structure in x-direction seen especially in bias (full) frames.
  
  The average column of a combined master bias frame. The master bias was combined from 11 frames using iraf/zerocombine. The vertical black line indicates prescan and overscan region, red horizontal lines show the read noise for a given read-out-speed and the yellow line (zero) is to guide eye.

Bias structure

The bias structure is slightly different if only a portion (in x-direction) has been read out.
When reading only a window a few electron gradient is expected to be seen. However the structure appears to be stable. The "full frame" plot shows 24 bias frames, "window xsize=750" 14 and "window xsize=500" 17 frames (however see below about "window xsize=500").

Window the first pixel in x

As shown above the "window xsize=500" appears to have variable bias structure.
The above plot shows the bias profile when the position of the window has been moved from left to right. The profile in x-direction is almost identical when the first pixel is either 800 or 1500, however for the x1=10 window the profile is clearly different. This can be seen also from the "bias structure plot" (above).