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Old 15-08-2012, 02:51 PM
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gregbradley
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Join Date: Feb 2006
Location: Sydney
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Hi Rolf,

Isn't the deep mag 24 a result of the long total hours rather than the number of subs?

Each time you do a sub the signal has to rise above the noise floor to be added to the signal. So faint details may in fact be lost as they are never recorded in the first place in short exposures. Adding exposures doesn't work unless the signal rises above the noise floor otherwise the faint signals are lost in the noise.

The limiting factors are more tracking accuracy, QE, mono versus one shot colour, weather, well depth, cooling power of the ccd to get noise lower and total exposure time.

In the end we need highest possible QE with lowest noise and signal recorded above the noise floor of the system to detect a signal.

Same chip in different cameras can perform slightly better with the correct supporting low noise electronics and more powerful cooling. Most of the modern camera makers are now quite close with their top of the line cameras for the same chip. It used to be a larger gap between some.

Level of seeing and long or short focal length comes into it but thats really a different topic of matching CCD camera to your optical system. Some work much better with some setups than others. Look at STL11/FSQ106 images for example. They match really well. So does the 16803 chip with just about anything. 8300 chip is also very good but more suited to faster focal lengths.

Greg.
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