now I see what type of photo your aiming at. Yes, that's the time where the light changes with every minute!
Reading your data, I wondered why you didn't reduce shutter speed to 1/50sec (at 28mm focal length) and opened the aperture to 5,6 or even 4. That should be enough to turn ISO down to 400 and give a nice low noise pic. To stabilize your shot, perhaps you can at least lean at your car.
Also you could zoom out a little more (wider) so that camera shake is less likely to ruin your shot. This type of pic comes out quite well, when you can see a lot of sky, also your depth of field increases with a wider focal length.
I did somethig similar, see here: http://www.flickr.com/photos/38912116@N00/373755621/
with 20mm F/3,8 1/60 ISO-200 (plus the built in flash for the tree...) on standard automatic. Although I admit that the lens has optical stabilization, but the 1/60sec should easily be enough.
Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews
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