iMovie, Mac Mini, High Def video capture

I have a Intel Mac Mini and a Sony High Def video camera. The mac mini does not have a large hard drive on it, but does just fine for capturing standard def content and then moving the content to my NAS but high def content can take up 5-10 times more space which my mac mini does not have free on the local hard drive. I do have a WD 500gb My Book Pro external drive and also a 1.3TB NAS. Is there a way I can capture the high def content directly to the external firewire drive?