[Entropy]

How does one go about choosing an appropriate camera for a particular scope ?
I have downloaded CCD Calculator, but i do not know what type of bandwidths i should keep things like Image Scale in between.
What is considered to high a arcsecond/pixel value ? And can you go too low ? is there a sweet spot ?
Will a good 'nebula' camera also be good at planetary imaging ?
Im mainly after a camera for DSO images, but would also like to take the occasional photo of jupiter/saturn ?
Im looking at buying a lx200ACF 10". And was tentatively tossing up between a QHY8, SBIG ST-7 or a canon 40d.