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Tele Vue 21 mm Ethos 2" Eyepiece - ETH-210

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SKU: TLV-ETH-210
 

Free Threaded Eyepiece Case with Purchase!

Free Eyepiece Case

Receive a free eyepiece case when you buy this eyepiece from High Point Scientific! You will love the way the two piece “bolt-style” case threads together to securely protect your new eyepiece from dust, moisture, and scratches during storage.

Tele Vue 21 mm Ethos 2" Eyepiece

The concept for this eyepiece series was proposed by Tele Vue President David Nagler, with performance parameters giving it the fundamental characteristics (the ethos) of a Tele Vue eyepiece: high contrast, comfortable eye relief and full field sharpness. Control of astigmatism, field curvature, lateral color, angular magnification distortion correction, and low pupil sensitivity for daytime use were specified criteria.

The 21 mm focal length completes the logical set of 21 mm/13 mm/8 mm and nicely juxtaposes the 17 mm/10 mm/6 mm combination. Each step within these two sets approaches a 3x field area gain. The 21 mm's effective field stop diameter is 36.2 mm, bringing its true field close to the 35 mm Panoptic. Its true field is also larger than the 26 mm Nagler.

Example use: In an f/4 Dobsonian, the exit pupil is just 5.25 mm using the 21 mm Ethos instead of 8.75 mm with a 35 mm Panoptic, or 6.5 mm with a 26 mm Nagler.

Following Tele Vue's philosophy of pushing the state of the art, long-time Tele Vue employee and optical design protégé Paul Dellechiaie took up the challenge and designed the basic eyepiece form. Under Al's guidance, Paul tweaked his design to fulfill the original goals. Sharp images are inherent to the optical design, but contrast is maximized through the intelligent use of flat finished baffles and ultra low reflectance, high efficiency coatings tuned to the composition of each element. Apparent Field of View provided will be 100° or 110°, depending on the model chosen.

Tele Vue Ethos Eyepiece Specifications:

  • Focal Length: 21 mm

  • Barrel Size: 2"

  • Apparent FOV: 100°

  • Eye Relief: 15 mm

  • Field Stop: 36.2 mm

  • Weight: 2.25 lb