Hey Greg,
Heres a reply from Terry.
"It will be a firmware difference, rather than a hardware one. The light edge will be caused by a minor transient voltage change as the line readout begins.
I can't be sure which version didn't show this, but I might be able to locate it. However, it is a very low level effect and is completely removed if you subtract a bias frame."
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Nah I use MaximDL's AO Guider feature. I've been thinking about trying CCDSoft, but havnt got around to trying it out yet.
Looks like Reduction Groups is CCDSofts option?
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*added Bias frame to the above images.