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Mar 6, 2003 Ghost Image


If the cloud was there, it should have showed up on the images that I took the next night [Mar 7] as well.
The CCD controller can give a "short circuit" signal or as they call it a reset signal to erase CCD contents. It's more like a capacitor discharge. This “short circuit” is based on transistors, which have resistance. It’s more like a resistor than a short circuit wire. It takes time to discharge. The default timing is enough for most applications. It must be a controller malfunction, and/or the user before me took a really very long bright exposure. I think it’s the first, a controller malfunctioned and didn’t apply reset as it should be or didn’t apply a long enough rest signal, or the reset signal was not received correctly by the CCD (most likely cause). Electric noise can affect controller’s signals, and thus misinterpreted by the CCD electronics.
One way to avoid this is by taking a short dummy image and through it. This does not happen very often.