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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Eyepiece | 7/7 | https://en.wikipedia.org/wiki/Eyepiece | reference | science, encyclopedia | 2026-05-05T09:47:24.682125+00:00 | kb-cron |
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 TeleVue 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 several 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 20 mm eye relief. The number of elements in a Nagler makes them seem complex, but the idea of the design is fairly simple: every Nagler has a negative doublet field lens, which increases magnification, followed by several positive groups. The positive groups, considered separate from the first negative group, combine to have long focal length, and form a positive lens. That allows the design to take advantage of the many good qualities of low power lenses. In effect, a Nagler is a superior version of a Barlow lens combined with a long focal length eyepiece. This design has been widely copied in other wide field or long eye relief eyepieces. The main disadvantage to Naglers is in their weight; they are often ruefully referred to as ‘hand grenades’ because of their heft and large size. Long focal length versions exceed 0.5 kg (1.1 lb), which is enough to unbalance small to medium-sized telescopes. Another disadvantage is a high purchase cost, with large Naglers' prices comparable to the cost of a small telescope. Hence these eyepieces are regarded by many amateur astronomers as a luxury.
== Electronic eyepieces == An electronic eyepiece, also called digital eyepiece or smart eyepiece, is a type of eyepiece that incorporates digital technology—such as cameras or electronic enhancements—and may also feature built-in lighting.
== Footnotes ==
== See also ==
== References ==
== Sources ==
== External links == Media related to Eyepieces at Wikimedia Commons EYEPIECE EVOLUTION Archived 2021-02-27 at the Wayback Machine A. Nagler – United States Patent US4286844 A. Nagler – United States Patent US4747675 A. Nagler – United States Patent US4525035 A. Nagler – Finder scope for use with astronomical telescopes The evolution of the astronomical eyepiece, in-depth discussion of various design and theoretical background John Savard's Eyepiece Page, a list of eyepieces with some details of their construction. United States Patent Office: Ultra wide ocular NAGLER.