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"Normal" cameras often don't use CCDs, they have CMOS sensors. Standard DSLR cameras and point and shoots as well have a filter that is designed to block infrared. This also has the effect of blocking Ha (hydrogen alpha) emission in the red part of the visible light spectrum that are a major component of the light coming from many emission nebula (Eta Carina, Tarantula, M42 etc all emit strongly in Ha). These cameras will still capture images but loose some detail as a result on those objects. They are still fine for objects other than emission nebulae, eg galaxies, PNs etc.
DSLRs can be modified to remove this filter (you see these referred to as here as "modded" DSLR's) or Canon currently sell the 60Da which is modded in the factory. This can have effects on their use as a regular camera so are often only used for astro work.
Astronomical CCDs as I understand have minimal if any filters. i am certainly not an expert on CCDs so will leave it to others to help with these!
Cheers
Malcolm
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