Tele Vue 21mm Ethos Eyepiece - 2 inch
| Article number: | ETH-21.0 |
| Availability: | More on the Way to us |
| Delivery time: | More on the Way to us |
* The Televue 21mm Ethos Eyepiece provides a 100° apparent field for a true "spacewalk" view of the night sky.
* With an effective field stop diameter of 36.2mm, the true field of the 21mm Ethos is close to that of the much loved 35mm Panoptic.
* Televue 21mm Ethos Eyepiece provides a generous 15mm of eye relief for comfortable observing.
* Accepts DIOPTRX eyesight astigmatism correctors.
* The Tele Vue 21mm Ethos Eyepiece has a dedicated 2" barrel.
* Dramatic mid-level magnification views combine with stunning wide field backgrounds.
| 21-mm | |
| Model # | ETH-21.0 |
| Focal Length (mm) | 21 |
| Barrel Size (in.) | 2" |
| Apparent Field of View (deg.) | 100 |
| Eye Relief (mm) | 15 |
| Weight (lb / oz) | 2.25 / 36.0 |
| Field Stop (mm) | 36.2 |
“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.