Details
The Ethos 21mm eyepiece 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.
21mm Ethos Specifications
- Apparent field: 100°
- Focal length: 21mm
- Effective field stop: 36.2mm
- Eye relief: 15mm (accepts DIOPTRX eyesight astigmatism correctors)
- Barrel size 2"
- Weight: 2.25 lbs (36.0 oz.)
Additional Information
| Model | ETH-21.0 |
|---|---|
| Weight | 2.0000 |
| Custom Stock Status | |
| Eyepiece Apparent FOV | 100 |
| Eyepiece Apparent FOV2 | 0 |
| Eyepiece Barrel Size | 2" |
| Eyepiece Eye Relief | 15 |
| Eyepiece Eye Relief 2 | 0 |
| Eyepiece Field Stop | 36.2 |
| Eyepiece Focal Length | 21.0 |
| Eyepiece Focal Length2 | 0.0 |
| Eyepiece Elements | 0 |
