Excessive noise with 7D and astrophotography

My friend has a nice telescope that he uses to do some astrophotography. He typically uses his Nikon D80 and multiple long exposures. He then stacks them later on. This last weekend we were using my 7D. The shots were were getting with the 7D were substantially more noisy than with his D80. Both cameras were shooting raw with all noise reduction turned off. I was using about ISO1600 most of the time but so was he at times. From what I have read the 7D should be much less noisy than the D80 since it is higher end and newer. Am I doing something wrong?