The Baader Planetarium 31 mm Hyperion Aspheric Eyepiece is one of the world"s first to incorporate aspheric surfaces. This new technology has allowed Baader to eliminate eyepiece aberrations without the usual penalty of extra lens elements, excessive size and weight, or higher .The clever use of 2" x 24 tpi SCT threads for attaching the 2" barrel permits the Hyperion-Aspheric to directly thread onto the rear cell of popular SCTs. This results in the highest rigidity possible for imaging. Two barrel sizes are provided with each Hyperion Aspheric. The standard 2" barrel provides the full 72-degree field of view and a special wide field 1-1/4" barrel provides the maximum true field ever in this barrel size, with a field stop of 1.265" (32 mm) - perfect for extracting every bit of field possible in 1.25" focusers or bino-viewers.