CCD cameras

[OzStarGazer]

Hello,

I was just wondering if there is a huge difference between normal cameras with a CCD sensor and the CCD cameras specifically sold for astronomy. I have read that many of the cameras sold for astronomy have an IR filter. Is this the main difference?

[barx1963 (Malcolm)]

"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

[OzStarGazer]

Thanks for the great explanation, Malcom. I was curious because I saw a few threads mentioning "CCD cameras", and I bought a Canon point-and-shoot camera about a month ago which also has a CCD sensor. It is not the latest model though. The latest models seem to use the CMOS sensor you mention.

[OzStarGazer]

Sorry, one more question... I have read that they say to use an IR-cut filter to take pics when using an UHC filter. Do I need an additional IR-cut filter or is the one that apparently comes with all normal/standard cameras enough? It looks like the pics taken when using an UHC filter are not so nice (although the real view through the telescope is much better), so I was wondering if it is because I need an additional IR-cut filter? Or does that statement only refer to astronomical CCD cameras without the IR-cut filter?