DELOS 17.3mm, Ø 31,8mm

It was natural to take lessons learned from the tremendously successful Ethos project and apply it going forward. In the fall of 2008, Paul Dellechiaie was tasked to investigate a long eye-relief eyepiece design in the 70° AFOV range, retaining the key performance goals met with Ethos. My father named Paul's design, "Delos." Delos is a beautiful Greek island which happens to be the mythical birthplace of Apollo, god of light. More importantly the name was chosen to give recognition to Paul, principal designer of both Delos and Ethos. — David Nagler

Tele Vue is pleased to introduce the Delos, mid-to-short focal length line of 20mm eye-relief, 72° apparent field of view eyepieces. Every optical, mechanical, and ergonomic aspect was rethought to achieve reference-standard performance for any visual application.

The Delos was conceived as a narrower field Ethos. Reducing the field to 72° allowed freedom to increase eye-relief, while controlling pupil aberrations, all without making the eyepiece too large. With Ethos performance standards as benchmarks, the Delos design achieves full field sharpness, virtually perfect f θ (theta) distortion mapping, and color neutrality. Image fidelity is maximized utilizing glass matched multicoatings and anti-reflection surfaces throughout the eyepiece.

Contrast is further enhanced with a new, continuously adjustable height eyeguard system that can be locked in any position. Since the Delos eye-lens measures a quite large 35mm in diameter, preventing stray light from reflecting off the first surface and extraneous light from entering your eye pays off in a nice increase in perceived contrast. The eyeguard's sliding action allows for positioning the soft rubber eyeguard at the ideal height to suit the observer's preference. Indicator marks on the eyepiece body are handy reference guides for setting your perfect position. The eye-guard can also rotate for Dioptrx users.

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.

Warranty

We are pleased to offer a Lifetime Limited Warranty on all eyepieces, Barlows, Powermates, and Paracorr products for the original owner and a 5-year warranty for all other products for the original owner. You also have the security of knowing that every current Tele Vue eyepiece can be repaired, serviced, or cleaned at the factory. Tele Vue eyepieces are also great investments, returning high resale values, when you want to upgrade or modify your collection.