Tele Vue 21mm Ethos Eyepiece - 2 inch
| Article number: | ETH-21.0 |
| Availability: | In stock |
| Delivery time: | In Stock |
The 21mm Ethos is a premium 2" eyepiece featuring a massive 100° field of view, ideal for deep-sky and wide-field observation. With 15mm of eye relief and fully multi-coated, 9-element optics, it delivers exceptional sharpness, contrast, and immersive views across the entire field.
Specifications
- Focal Length: 21 mm
- Barrel Size: 2" (50.8 mm)
- Apparent Field of View: 100°
- Eye Relief: 15 mm
- Field Stop Diameter: 36.2 mm
- Optical Design: Proprietary design with 9 elements in 6 groups
- Coatings: Fully multi-coated optics with blackened lens edges
- Weight: 36 oz (1020 g)
- Dimensions: Approximately 3" (7.5 cm) in diameter; 4.3" (10.9 cm) in length
- Filter Threads: Standard 2" filter thread (M48 x 0.75)
- Barrel Features: Safety undercut for secure locking
- Eyeguard: Fold-down rubber eyeguard
- Compatibility: Accepts Tele Vue Dioptrx astigmatism-correcting lenses
“You've got very innovative engineers always managing to break the laws of optics. This Ethos is out of this world!”
—J.G., France
The 21mm focal length completes the logical set of 21mm/13mm/8mm and nicely juxtaposes the 17mm/10mm/6mm combination. Each step within these two sets approaches a 3x field area gain. The 21mm's effective field stop diameter is 36.2mm, bringing its true field close to the 35mm Panoptic (38.7mm Field Stop diameter). Its true field is also larger than the 26mm Nagler with its 35mm effective field stop diameter. In an f/4 Dobsonian, the exit pupil is just 5.25mm using the 21mm Ethos instead of 8.75mm with a 35mm Panoptic, or 6.5mm with a 26mm Nagler.
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