Quote:
Originally Posted by gregbradley
I think you have made an error there. QE determines sensitivity not pixel size. That's what QE means - what percentage of photons hitting the pixel result in a signal.
Pixel size determines resolution.
It will be more sensitive than the 9 micron cameras with 60% QE. I have both 16803 and 8300. They both have 60% QE. The 8300 is 5.4 mcirons, the 16803 is 9 microns. I don't see any difference in sensitivity. The seem much the same on several different scopes. The resolution is different as is the FOV and more importantly the smaller wells make it more sensitive to bright stars and losing colour and halos around bright stars.
There may be a slight loss with smaller pixels due to the antiblooming channels around the pixel resulting in a larger percentage of surface area taken up by them. Also perhap QE of these sensors may vary with F ratio of the scope in that super fast scopes may give a steeper light cone less suitable for a pixel receiving light.
SBIG ST10XME has been the highest popular QE camera and it has 6.6 micron pixels (and non antiblooming).
Greg.
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Thanks for the response Greg.
There is no error. The number of detected photons (the signal) depends on the quantum efficiency and the number of photons actually entering the pixel - this depends entirely on how big the pixel is - a big pixel intercepts more photons than a small one with a given scope. That's how binning works - it makes bigger effective pixels to increase the sensitivity. Sampling is maybe the single the most important determinant of how sensitive a system is and yet it seems to be often relegated to being a minor afterthought.
Regards Ray
For confirmation, the following is a quote from the Apogee website at
http://www.ccd.com/ccd113.html
note that the assumed seeing is somewhat worse than I have worked on, but the message is the same.
"
Pixel Sensitivity
The larger the pixel, the more sensitive the camera will be for any given focal length. This is also a sampling issue. Under excellent seeing conditions, a camera with 24µ pixels on a telescope of 2000 mm focal length will produce images that are very close to being undersampled. For faint deepsky objects, however, these large pixels will outperform (in terms of sensitivity) a camera with 9µ pixels on the same telescope. This is because a camera with 9µ pixels being used on a telescope with 2000 mm focal length will produce images that are nearly oversampled. That is, there are too many pixels making up each star image. The result will be reduced sensitivity, but better resolution."