Asked Mark Foster
CMOS (Complementary Metal-Oxide- Semiconductor) and CCD (Charge Coupled Device) are both types of sensors used in digital imaging. Both use slightly different methods of operation and setup, therefore have pros and cons for certain uses.
In general there is a small bias towards CCD in astrophotography. This is due to the signal-to-noise performance of the sensor. This allows them to be more accurate over long-exposure shots. This is also aided by a more uniform readout across the entire sensor, something that some CMOS chips struggle with. It isn’t all bad news for CMOS devices though as they in general have much faster readout times and it’s a much younger technology than CCD so improvements are being made much quicker.
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