"The Baader Planetarium 17 mm Hyperion 68-degree Eyepiece offers world-class performance and unique photo-visual features. No longer do amateurs need to spend more on their eyepieces than their primary instrument in order to get true high-end performance in a wide-field eyepiece. Not just a different branded version of their highly regarded cousins, the Hyperion have been totally redesigned to deliver better transmission, contrast and useful new features.Baader Planetarium has worked hard to give the Hyperion the world's finest optical coatings, superb mechanics and their unique multifunctional design. As a visual eyepiece, the Hyperion delivers superb sharpness and color fidelity across their 68-degree wide, flat-field even in fast telescopes. In comparison to the Pentax XL eyepieces, the Hyperion matched the Pentax in every regard.From their superb on-axis and off-axis sharpness to their pitch-black high contrast field, the Hyperion really works. Viewing through a Hyperion is notably comfortable and relaxing due to their forgiving eye-position, 20 mm of eye-relief, extra-large eye lens and an optical design that is free of annoying 'kidney-beaning' and blackouts.|Consisting of 8 elements in 5 groups (3.5 mm - 21 mm), the Hyperion optical design delivers outstanding sharpness and color correction over a 68-degree wide apparent field (65 degrees for the 21 mm)|The Hyperion optical design has been chosen to deliver a exceptionally comfortable view, thanks to its 20 mm of eye-relief, large eye lens, and a pupil-free of the kidney-beaning and blackouts common in many wide field eyepieces|The new 24 mm uses a different optical design and delivers outstanding performance over its 68deg. wide apparent field. It is totally free of blackouts & other annoying exit pupil behaviors, delivers long eye relief (17 mm), virtually zero distor|Its flat focal plane is particularly suited to very fast newtonians that use coma correctors. The 29 mm field stop makes the 24 mm Hyperion the widest 24 mm eyepiece. The 24 mm Hyperion is also the smallest and lightest of the Hyperion|High grade water-white glasses are used throughout to deliver a crystal clear view with low scatter and excellent color fidelity, free of the yellow or bluish coloration imparted by many other eyepieces. Use of high-index glasses delivers low distort|Baader Planetarium has gone to great lengths to give the Hyperion the most advanced multi-coatings ever used on amateur telescope eyepieces|The Hyperion Phantom Group multi-coatings and coating equipment are proprietary to Baader and have been designed by German coating engineers specifically for the Baader Hyperion and optimized for each of the glasses used|These coatings are applied with the latest thin-film German coating equipment, training, and process controls. Users report that the Hyperion clearly shows fainter stars and darker sky than the competitive clones|The proprietary Hyperion housings have been engineered by Baader to incorporate careful opto-mechanical design and execution of internal baffling to eliminate stray light and ghost reflections|Uncapping the eye lens reveals a pitch black interior with no distracting and contrast-robbing glints of light from unbaffled lens or metal surfaces|Superb fit and finish - eyepiece barrels are accurate to size, nicely machined, and hard anodized|Works in both 1.25" and 2" focusers. The 1.25" barrel is threaded for filters and kept short (0.94") to work well in binoviewers and spotting scopes. Baader's new housing incorporates a full-length 2" barrel (0.94" long)|In addition, the Hyperion field stop locations have been re-designed and optimized to give the shortest focus position possible|Soft folding rubber eyecups work for both normal and eyeglass users. Each Hyperion comes with protective lens caps and leatherette storage pouch|All Hyperion accept popular Astigmatism Correcting Lenses. The Hyperion eyelens housing is compatible with the full range of correcting lenses from 0.25 to 3.5 diopters|Observers with any astigmatism will really appreciate this feature, no longer needing to wear eyeglasses to see stars as true pinpoints|The long 20 mm eye relief of the Hyperion works particularly well with these corrector lenses, without forcing the observer to press their eye close to the lens in order to see the entire wide field|Removable Negative Lens Element permits variable focal lengths using Baader's new 14 mm and 28 mm Finetuning Rings (sold separately)|The optical design of the Hyperion enables them to work as an extremely sharp wide-field projection eyepiece for even large chip CCD and DSLRs|The eyelens barrel has been provided with two different external threads, M43 and M54 (these are covered by the removable rubber eyecups)|A wide variety of adapter rings enables cameras to be directly and rigidly close-coupled for afocal projection photography, or variably extended for classical eyepiece projection imaging with T-Adapters and Extension Tubes|The front negative lens element is designed to be removed (and exposes an M48 2" filter thread). This converts each Hyperion into a longer focal length high-quality projection eyepiece, giving the imager two choices of focal length with each eye"