I'm down close to 12 inches now and I think I'm going to call it good. After that, I'm NEVER digging another hole in this yard again! The ground here is horrible and it's like trying to dig through a freeway. Time to look for a good deal online for power cable and some CAT6 (or possibly 6a) cable. I feel so far behind with this project.
Here is a low angle, dramatic shot (makes it look really deep).