RAW vs JPEG

[MartinB]

The big advantage with RAW is that the images typically are 12 bit depth as opposed to 8 bit. This means that each pixel can hold far more information. This is particularly important in astrophotography because most of the data is held a low light levels despite long exposure. 12 bit allows much more detail to emerge when the histogram is stretched to brighten the image

[x6gas]

You get a lot of performance from cooling the chip. The dedicated astro CCD camera is the way to go, if you're really serious about DSO imaging.

That's a really good point. My experiments looking at amp glow on the D40 and D40x show a big dependance on ambiant temperature and this is, of course, in addition to the senor being noisier at higher temperatures...

I've seen some extremely modified DSLRs where the IR cut filter is replaced with a baader filter and they are cooled and re-housed but I can't really see the point given the ATiK cameras seem quite reasonably priced (especially the Titan). Fair enough if you're starting with a £10 webcam but is it worth the effort with a DSLR that cost a couple of hundred quid or more... especially if you can't use it for normal photography...

I think I'll make do with my Nikons but if and when I do feel the need for cooling then I think it'll be a dedicated astro CCD...