The TeleVue 8mm Ethos eyepiece raises the bar for shorter focal length eyepieces. It expands the apparent field of view to an astonishing 100°, while matching all the key performance criteria of its highly-acclaimed 13mm big brother.
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. With a usable eye relief of 15mm, the 8mm Ethos might normally somewhat vignette the field of view for some 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 8mm Ethos has all the virtues that 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 composition of each lens element.
Compared to any longer focal length eyepiece (even the 13mm Ethos), the higher magnification of the 8mm Ethos provides a darker sky background, with fainter stars becoming visible and more detail showing in all deep sky objects. With its incredible 100° field, the 8mm Ethos gives you dramatic views that are simply not possible with a similar focal length eyepiece, no matter what telescope you use. In addition, the smaller exit pupil of the 8mm reduces eyesight limitations due to astigmatism when compared with longer focal length eyepieces.
The 8mm 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. A rubber grip ring provides a sure grip in cold weather when wearing gloves or mittens.
The 8mm Ethos has a maximum barrel diameter of 53.4mm, making it usable in many binoviewers for the majority of (but not all) observers. In a binoviewer, a pair of 8mm Ethos eyepieces provides the ultimate in virtual 3-D "spacewalk" observing.
The 8mm TeleVue Ethos eyepiece will accept TeleVue Dioptrx eyesight astigmatism correcting lenses. It is parfocal with TeleVue Radian, Plössl, Type 6 Nagler, and 1.25" Panoptic eyepieces.
