Invented by Albert Nagler and patented in 1979, the Nagler eyepiece is a design optimized for astronomical telescopes to give an ultra-wide field of view (82°) that has good correction for astigmatism and other aberrations. Introduced in 2007, the Ethos is an enhanced ultra-wide field design developed principally by Paul Dellechiaie under Albert Nagler's guidance at Tele Vue Optics and claims a 100–110° AFOV. This is achieved using exotic high-index glass and up to eight optical elements in four or five groups; there are five similar designs called the "Nagler", "Nagler type 2", "Nagler type 4", "Nagler type 5", and "Nagler type 6". The newer Delos design is a modified Ethos design with a FOV of 'only' 72 degrees but with a long 20mm eye relief.