ΠΡΟΣΟΦΘ.ΤeleVue NAGLER ΖΟΟΜ 3-6mm

I did not set out to design a zoom eyepiece, per se. David and I were discussing characteristics we'd like in a superior "planetary" eyepiece, and the zoom feature answered one of the major goals; how to obtain the highest possible useful magnification on a given night considering the ever-changing atmosphere. There were other aspects of equal importance and only the combination of all would satisfy our ethos in creating a "planetary" eyepiece: full field sharpness for any speed telescope, high contrast and transmission for natural color rendition, low scatter, and comfortable eye-relief. Being a zoom, we also concerned ourselves with making sure it was parfocal through the zoom range as well maintaining a constant apparent field of view. The one aspect we were not too concerned with was giving the eyepiece a wide AFOV.

Limiting the AFOV to 50° and the eye-relief to 10mm, we were able to create a compact physical design employing only five elements to reach the optical goals. Like other "Naglers," it utilized a negative lens group ahead of the focal plane. This permitted relatively long eye-relief for very short focal lengths. By independently moving the upper and lower lens groups, we achieved constant focus (parfocality), constant apparent field of view, and essentially constant eye-relief. Just by rotating the upper barrel, you can zoom through the power range. Click stops offer known power points for reference without needing to look at the barrel and instantaneously choose the optimum magnification for the given observing conditions.

I was sufficiently confident in the design and purposely decided to attach my name to the zoom, despite the common association between "Nagler" and 82° AFOV. I felt it was more important to stake our reputation on overcoming the "degrading zoom reputation" than maintaining the 82° assumption for "Nagler" designs.

— Al Nagler

Why Choose Tele Vue Eyepieces

"Your eyepiece is half the telescope, use the best -- Tele Vue" - said Jack Marling, founder of Lumicon Co. "Fast" telescopes (f/4-f/6) of all types -- refractors, reflectors, Schmidt Newtonians, Mak-Newtonians require the finest eyepieces for sharp, full field viewing. Every Tele Vue eyepiece is personally tested at f/4 by our quality control staff to ensure the sharpest full field possible. It is the nature of optics that being the best in fast scopes also always assures the best performance in "slow" scopes. While every Tele Vue eyepiece type will yield the critical center sharpness so necessary for planetary viewing and splitting double stars, observers get the added bonus of a sharp wide field and comfortable eye relief with the different design models. The Tele Vue 50° Plössls are patented to be sharper over a larger field than any competing brands of Plössls or Orthos. Tele Vue 62° DeLite, 68° Panoptics, 72° Delos, 82° Naglers and 100° Ethos are the eyepieces of choice, along with the 50° Nagler 3mm--6mm zoom, for full field sharpness. The finest performance requires the finest materials such as high index lanthanum and fluorite type glasses, in some cases costing up to 15x more than ordinary glass types. At Tele Vue we ask "how can we make it better", rather than "how can we make it cheaper." We think you'll agree that the views are worth it.

Design

An optical design incorporates a number of lens elements utilizing different glass materials and shapes. Elements cemented together are called a group. Each Tele Vue design is configured to achieve the sharpest full field, with the number of elements and groups minimized, while yielding the largest possible true fields and eye relief. Some design types are "scaled", that is, one form is "scaled" to provide a range of focal lengths. Note that eye relief, size and weight "scale" along, but image quality and apparent field remain constant. Examples of "scaled" Tele Vue designs are Plössls, Panoptics and the Nagler type 5. Other designs set a particular characteristic, such as eye relief, and tailor each focal length in the series as individual designs. The size, weight and number of lens elements will vary little within a given series. Examples are: DeLite and Delos, with 20mm eye relief, Nagler type 4 models with approximately 18mm eye relief, Nagler type 6 eyepieces with 12mm eye relief, and Ethos eyepieces with 15mm eye relief.

We are gratified that Tele Vue eyepiece designs over the past 35-years have reached almost iconic status. New innovative designs, improved materials and coating techniques have allowed Tele Vue to continually produce what many consider to be the best eyepieces available in the world. As a result, discontinued eyepieces, such as the "Wide Fields" and original Nagler and Nagler type 2 models, have often become collector items that can sometimes sell for more than their original cost. The "Backyard Astronomers Guide" notes: "Al Nagler has introduced more innovations in telescope eyepiece design than anyone else in the history of amateur astronomy." Indeed, every Tele Vue Plössl, Wide Field, Panoptic, and Nagler eyepiece is based on patents by Al Nagler. Other accessories -- such as Barlows, Powermates, and the Paracorr (coma corrector for fast Newtonians) -- are also original Nagler designs. Paul Dellechiaie, long-time Tele Vue employee working under Al's guidance, designed the Ethos, Delos and DeLite series.

Construction

Every Tele Vue eyepiece is fully multi-coated, has blackened lens edges and anti-reflection threads for maximum contrast. Chrome plated barrels, which resist scratching and marring better than black anodized barrels, include safety undercuts and threads for filters. Upper barrels are black anodized aluminum with a rubber grip ring, engraved identification, and fold down rubber eyeguards. All Nagler type 4, DeLite, and Delos models include an adjustable eyeguard for ideal eye positioning. Protective caps are included for top and bottom. Many of the 1¼" Plössl, DeLite, Delos, Panoptic and Nagler models are parfocal for convenience.

Manufacture and Quality Control

All Tele Vue eyepiece designs are proprietary and are manufactured in factories in Japan and Taiwan that do not make competitive products. To assure outstanding manufacturing and flawless image quality, our in-house NY staff performs optical and cosmetic testing on every eyepiece made, using our patented 5" f/4 flat field "MPT" test refractor. We even ship Japanese made eyepieces to our Chester, NY facility for 100% quality control and then re-ship them back to our Tele Vue Japan distributor for sales in Japan. In fact, focal length control is so uniform that we have never seen a mismatch that would affect use in a binoviewer, when using any vintage version of a given eyepiece model with a newer one of the same model.