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Nice shot. Can I ask why you chose ISO400? It seems a bit slow.
I always used the maxium ISO like 1600 or 3200. 400 is taking too long, its like stopping down a F2.0 lens to F5.4.
I have hear dsome say ISO800 gives better depth. Perhaps that is true and but if oyu have darks and flats and bias to subtract then I say go the max and hit it at ISO1600 or 3200.
Just be careful with DSLRs as they often show the stars as all white whereas there should be a variation in colour. I think that is because the star overexpose first so you can go too long. I have heard expose to 1/3rd of a histogram meaning that the hstogram is 1/3rd the screen or expose to the limit of your light pollution as that will hit a ceiling before the object will.
So at a dark site you go longer and higher ISO especially in summer and at a light polluted area you go shorter and more of them and use a light pollution filter.
That's where the 40D comes into its own with the 14 bit converter, stars are more likely to have colour.
Greg.
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