A review in Sky & Telescope magazine gave the 13mm Ethos five stars, meaning “Sensibly perfect. No meaningful improvements possible.” The reviewer commented, “As revolutionary today as the original 13-mm Nagler eyepiece was when it was introduced in 1981, the 13-mm Ethos sets a new standard for wide-field observing. The on-axis performance is second to none, while the 100° apparent field is unprecedented for an astronomical eyepiece . . . if I were dropped on a desert island tomorrow with the 12-inch scope and only one eyepiece, I’d want it to be the Ethos.”
With a 13mm focal length that evokes that of the original and revolutionary 13mm Nagler eyepiece, the field of this new 100° apparent field Ethos eyepiece is nearly 50% larger in area than the 82° field of a “space-walking” 13mm Nagler. The TeleVue Ethos delivers the true field size of a longer focal length (but narrower apparent field) eyepiece, but has the benefits of the higher power and darker sky background that are inherent in a shorter focal length.
There is a soft rolldown eyecup to shield the eye from ambient light (from a neighbor’s security light, for example) and improve the image contrast. At a usable eye relief of 15mm, the 13mm Ethos would normally somewhat vignette the field of view for eyeglass wearers. However, since the 100° field is so wide that you can’t see the full field without having to move your head from side to side to take it all in anyway, vignetting in the conventional sense is not a problem.
The 13mm Ethos has all the virtues that professional and amateur astronomers have come to expect from a TeleVue eyepiece: high contrast, comfortable eye relief, and full field sharpness – with well-controlled astigmatism, field curvature, lateral color, angular magnification distortion correction, and low pupil sensitivity (kidney bean effect) for daytime use. While sharpness is inherent to the optical design itself, the contrast is maximized through the intelligent use of flat finished baffles and ultra low reflectance, high efficiency coatings that are tuned to the glass composition of each lens element.
The Ethos has concentric 1.25” and 2” barrels that allow it to be used in both 1.25” and 2” focusers and star diagonals without the need to change the diagonal or eyepiece adapter. A safety groove is machined into the 2” chrome barrel to engage your focuser thumbscrew. This will help prevent the eyepiece from falling should the thumbscrew accidentally loosen while observing.
The barrel diameter of the current version of the 13mm Ethos has been reduced slightly to 62mm, from the 63.5mm of the first versions to be shipped. This will allow the use of two 13mm Ethos eyepieces in a binoviewer, providing a minimum interpupillary distance of 62mm. This spacing will be usable for the majority of observers, but some people with narrower than average eye spacing may not be able to use this combination. If you are a very serious binoviewer astronomer, a pair of 13mm Ethos may be worth a try.
A commentary on a Cloudy Nights forum, quoted by TeleVue, said, “Forget about the 100-degree field (well . . . I know you can’t but . . .), this is quite simply the finest eyepiece I’ve ever seen – period! Contrast, sharpness, light-throughput, etc. are all just amazing. There is simply NO ghosting or other internal reflections . . . the background is jet-black and the stars (even in my 28” f/3.66) are absolute diamond-points to the very edge!(P> “I've owned and used all of the “gold standards” over the years and NOTHING I’ve seen can match this!
“Along with about a half-dozen other observers we did “A/B” testing with other top-of-the-line 13 and 14mm eyepieces (M-51, Thor’s Helmet and M-42 were the targets). EVERYONE agreed that the ETHOS seemed to add additional inches of aperture. The increased detail in all of the objects was instantly apparent!
”As a bonus, the fine detail on Saturn equaled or exceeded the best “planetary” eyepieces any of us had ever used. And, again, NO ghosting or internal reflections. This baby does it all.
“And, as for the 100 degree field, Vic said it best . . . ‘you feel like you're going to fall in’ . . . ‘the scope just gets out of the way and it’s like you're standing in space looking at the objects.’”
The 13mm TeleVue Ethos eyepiece will accept TeleVue Dioptrx eyesight astigmatism correcting lenses.