TS Optics Erfle 20mm 70° 1.25″ Eyepiece with Crosshair Reticle
Looking for an eyepiece that combines a wide, comfortable field of view with the ability to centre objects precisely? The TS Optics Erfle 20mm eyepiece with crosshair reticle is exactly what you need. The classic Erfle design delivers relaxed viewing with minimal distortion across the full image area. The built-in crosshair reticle opens up precise centring and measurement - whether for visual observation, mount alignment, or basic astrometry.
Wide field of view and versatile magnification
The 70° field of view places this eyepiece firmly in the wide-angle category, giving you a broad view of the sky while keeping the image natural and comfortable to look at. The 20mm focal length provides a versatile magnification that suits most mid-focal-length telescopes. It works especially well for open clusters, nebulae, and planetary overviews.
Multi-layer coatings on all optical surfaces reduce reflections and maximise light transmission. This makes a real difference when observing faint objects under light-polluted skies.
Crosshair reticle - precise centring and alignment
The integrated crosshair reticle is invaluable for anyone who needs to centre objects accurately, calibrate a mount, set up polar alignment, or measure object positions visually. The reticle can optionally be illuminated - the illuminator is not included as standard but is available as optional accessory. This makes the eyepiece fully usable even against a faint background sky.
A standard 1.25″ filter thread is built in, so you can attach any 1.25″ filter without adapters.
Comfortable to use - with or without glasses
The fold-down rubber eyecup lets you switch quickly between observing with and without glasses. The generous 17mm eye relief means you can see the entire field of view without pressing your eye close to the eyepiece. There is no need to search for the exact eye position - the view is there immediately. The 1.25″ barrel fits the vast majority of amateur telescopes available today.
Who is this eyepiece for?
This eyepiece suits astronomers who want a single eyepiece that combines a wide, comfortable field of view with a precise crosshair reticle - without compromising on optical quality or ergonomics. Use it for visual observing, mount setup, or as a practical tool for more accurate sky measurement. It delivers reliable results every time.
Key features at a glance
- Classic Erfle design - wide field with minimal distortion
- 70° apparent field of view
- 20mm focal length - versatile for most telescopes
- Built-in crosshair reticle - optionally illuminable
- 17mm eye relief - comfortable for glasses wearers
- Multi-layer coatings for maximum light transmission
- Fold-down rubber eyecup
- Standard 1.25″ filter thread
- 1.25″ barrel - fits virtually all amateur telescopes
Technical specifications
| Parameter |
Value |
| Design |
Erfle |
| Focal length |
20mm |
| Apparent field of view |
70° |
| Eye relief |
17mm |
| Barrel diameter |
1.25″ |
| Filter thread |
1.25″ standard |
| Reticle |
Crosshair, optionally illuminable |
| Coatings |
Multi-layer |
| Eyecup |
Fold-down rubber |
