Nodal slide
When you use the panning function on a tripod head to produce images for stitching into a panorama, parallax errors can be introduced. This is because the point of rotation is under the camera, so the view shifts as you rotate the head. To stop this, the point of rotation needs to be where the light rays diverge – the nodal point. A nodal slide sets your camera back, so the nodal point sits at the point of rotation. To use it, first ensure your camera is mounted vertically and remains level as you rotate it. Then choose a point in the foreground or middle distance you can line up with a point in the distance and rotate your camera to the left and see if the two points are still lined up at the edge of the frame, rotate to the right and check to see if the two points are still in line. If not move your camera backwards or forwards on the slide until they stay in line as you rotate the camera.