I walked around Oakwood this morning with the fisheye zoom lens while the sun was still fairly low. One issue using the fisheye lens when the sun is out is keeping your shadow out of the frame, which is actually impossible with the sun at your back. Another issue is keeping the bright sun out of the frame.
With both of these issues, trees are your friend. You can hide your shadow in the shadow of a tree and you can hide the sun behind a tree.
Here are some samples from this morning. I had more circular images that were good but were ruined by a bit of my shadow along the edge.