The Baader Planetarium 28mm Hyperion Fine Tuning Ring will allow you to easily change the focal length of your Hyperion eyepiece! Simply install it between the front element and the main body of the eyepiece. The Baader 28mm Hyperion Fine Tuning Ring is made to match the Hyperion finish and are fully internally sharp v-threaded and blackened to eliminate stray light reflections from the internal surfaces. The Baader 24mm Hyperion Eyepiece will not accept the Fine Tuning Rings due to a difference in optical design. With the addition of Baader's Fine Tuning Rings, your Hyperion eyepiece can now function as not one, but four eyepieces with the addition of the Baader 14mm Fine Tuning Ring. Both the 28mm Fine Tuning Ring and the 14mm Fine Tuning Ring have an outside diameter (OD) of 2" and are threaded with a M48 (filter thread) on each end, so they can be installed in between the removable front negative element and the main body of the Baader Hyperion eyepiece. The added spacing decreases the focal lengths (increases magnification), according to the table below. The Baader Fine Tuning Rings are made to match the Hyperion finish and are fully internally sharp v-threaded and blackened to eliminate stray light reflections from the internal surfaces. Another novel way to change eyepiece focal length is to use a Baader 2" Filter in between the Hyperion negative element and main body, just like a small Fine Tuning Ring. The 8.5mm thickness of the filter cell will have