450D Vs 300D

Have never used the 450D, but it's basically just a step up from the 400D, where as the 40D was already a couple of steps above it. Better build quality, weather sealing, ISO up to 3200, also has a separate settings LCD. 450D only takes SD cards, so any Canon user with a stash of CF cards is screwed. 6.5 fps compared to 3.5 fps on the 450D.

If it was my money, I'd be getting the 40D, it's just a better all round camera. I have a 400D and a 40D and the 400D feels like a toy compared to the 40D.

I believe however that the 450D has a live view through the lcd to help with focusing

Keith..

Which is one up on the 400D Keith, but the 40D has it too.

I don't see any solid astro reason that the 40D is worth the extra cash, as for canon build quality, I wouldn't worry about it.
Lightweight is good for astro equipment and the 6+ fps is of no advantage to us.
The 3200 iso is the only advantage I see but I want to see dark frames (noise) to see if its useful.
As for price..... I have a 300D which cost me the bones of a grand, what would I get for it on the open market???, a mere fraction of what I'd pay for it I'd suspect, so little infact that its not worth selling

In fairness I did say it was the better all round camera. Considering what can be done on here with a webcam, I would imagine you wouldn't be using the 450D/40D purely for astro stuff.

Those are fair comments but I would be using the camera mainly but not solely for astronomy, I see no advantages in the 40D for my use.