Parallax errors are a common problem in stitched panoramic images.
On the Nikon 990, for example, the tripod mount is about two inches away from the axis that runs through the lens. Tripod heads that offset the camera so that it rotates around the axis are available from companies like Kaidan , but can cost several hundred U.S. dollars. Additionally, most of these heads are only designed to work with the camera in the portrait orientation. Because most of my stitched photographs are taken with the camera in the landscape orientation, and I rarely use the fish-eye or other auxilliary lenses that are popular with panorama photographers, I decided to make my own tripod head. As a guide, I used Judy Arndt's diagram showing the exact position of the nodal point for the Nikon 990.