"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.|The aspheric surfaces on the 31 mm Baader Hyperion Aspheric Eyepiece eliminates distortion without extra elements, weight|Supplied with a 2"" barrel and 1.25"" barrel|The 31 mm Baader Hyperion Aspheric Eyepiece threads onto the back of most SCT rear cells, producing a rigid connection for imaging|A wide 72-degree field of view and excellent eye relief are hallmarks of this great eyepiece|The Baader Hyperion Aspheric eyepiece offers freedom from blackouts, kidney beaning, and lack of distortion, and combine with long eye relief to produce a view that is uncommonly comfortable and natural for all users|The ultra-wide 72-degree field of view of these eyepiece is extremely flat and without distortion, and are virtually free of angular magnification distortion|Baader's renowned Phantom Group Multi-Coatings and thorough internal baffling produce an extremely bright and high contrast view that is free of scatter|The Hyperion Aspheric eyepiece accepts Televue's Dioptrx astigmatism correcting lenses|The 31 mm Baader Hyperion Aspheric weighs 13.8 oz or 390 g"