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Good question. Each “pixel” on the sensor is a photo-site that has a “well depth”. Think of each photo-site as a bucket and think of incoming photons as droplets of rain.
Each ccd/cmos chip has a specific well depth, how many photons it can register before a bucket (photo-site) fills up and overflows (saturates).
For my ST7E ccd camera, I get saturation or star blooming spikes at around 58,000 photons, so when I take my Flats, I aim for an exposure which gives me a reading of around 15,000 to 20,000 which in my case, is shown by the camera control software, CCDSoft.
From memory, I think that my ST7E is a 16 bit camera so in theory the “bit depth” is 65,536, although it seems my “well depth” is only around 58,000 before the photo site overflows.
Cheers
Dennis
Last edited by Dennis; 30-05-2008 at 09:43 AM.
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