Originally posted by mutedphotos Votesh - What exactly are you looking for in terms of night photography? The shutter speed max will be the same regardless of the camera, so are you just needing better high ISO performance? If that's the case and you're looking at the D700 vs 5D, I'd say go for the D700. Not only is its noise performance on par with, or even a little better than the 5D, but Nikon also does a tremendous job of minimizing chroma noise so the resulting images have a more pleasing monochromatic noise pattern (looks more like film grain to me, instead of blotchy digital color noise).
What I'm mainly looking for as far as night sky shots go is better high ISO performance, but also the ability to use wide angle lenses as wide angle lenses. These would both help for the star shots I'm looking for. The shutter speed length for the same combination of aperture and ISO will indeed be the same, but by using a wider lens that does not further have a decreased FOV due to APS-C cropping, a longer exposure can be done while maintaining stars as points.
For example, if I got a 5D the first lens I would get would probably be the Mark I version of the 24mm f1.4. With this FL a shutter speed of 25 seconds would keep the stars a points. On the other hand, with my 31mm the longest shutter speed I can use on my K10D would be about 13 seconds to get the same effect. So with both lenses at the same aperture(say f2.0 because they both perform fairly well at this aperture from what I've seen), not only would I be able to capture twice the light but I'd have a wider FOV and better high ISO performance so I could kick up the ISO for even more light capture.
Like I've said though, this isn't the sole reason I'd get a 5D. I'm just in the market for a new body(I have pretty much everything I want as far as lenses go for Pentax, so my gear buying has to shift somewhere
). I have a feeling the 5D(which I'm heavily leaning towards just due to price) or D700(I've mostly ruled this out just because of the price of it and Nikon lenses in general) will be a much bigger improvement over the K10D than the K7 will. I'll have to get some new lenses, but there are plenty of lenses available for the Canon or Nikon systems that Pentax has no available competition for so I wouldn't be buying duplicate focal lengths for dual systems or anything like that. I'd really love to have the previously mentioned 24mm, and I'd probably get a T/S lens as well.