Baader Planetarium Hyperion 21mm 68° eyepiece - 2″/1.25″
If you are looking for an eyepiece that shows you the night sky in all its beauty and also gives you real technical flexibility, this is the right choice. The Baader Planetarium Hyperion 21mm eyepiece with a 68° apparent field of view is designed as a truly universal eyepiece for your telescope - and that is not just a marketing phrase. The Hyperion series was built from the very beginning with the diverse needs of the modern astronomer in mind, whether for visual observation or astrophotography.
Optical design and image quality
At the heart of this eyepiece is an 8-element optical system arranged in five groups. This design delivers a 68° apparent field of view with excellent sharpness across the entire image area. All optical surfaces are treated with a multi-layer FMC anti-reflection coating (Phase FMC), which guarantees a clean, neutral white image free from colour aberrations and unwanted reflections.
The internal blackening of the barrel is also very effective, eliminating stray light - something you will especially appreciate when observing bright objects or when working under light-polluted skies. The eye relief is a comfortable 20mm across all focal lengths in the Hyperion series, making extended observing sessions pleasant and relaxed.
Modular construction - two eyepieces in one
One of the most interesting features of the Hyperion eyepiece is its modular design. By unscrewing the negative front element, you convert it into a full 6-element 2″ Erfle eyepiece with a significantly longer focal length. This is ideal, for example, for wide-field views of large objects such as nebulae or open star clusters.
This feature makes the Hyperion an exceptionally good value for money: for the price of one eyepiece, you essentially get two different optical instruments with different focal lengths.
Ready for afocal photography
The Baader Hyperion eyepiece is fully prepared for afocal photography. The output section has two integrated camera threads - M54 and M43 - which are protected by rubber caps as standard. With the available adapters, you can connect practically any camera on the market. The rubber fold-down eyecup ensures comfortable eye placement during visual observation and easy camera attachment during photography.
Who is this eyepiece for?
The Hyperion 21mm is an excellent choice for astronomers who want panoramic views of large deep-sky objects - nebulae, star clusters, or galaxies - without making any compromise on image quality. Photographers experimenting with the afocal method will also find it very suitable. Compatibility with both barrel sizes (2″ and 1.25″) makes it a great companion for virtually any amateur telescope.
Key specifications
| Parameter |
Value |
| Focal length |
21mm |
| Apparent field of view |
68° |
| Optical design |
8 elements in 5 groups |
| Coating |
FMC multi-layer anti-reflection (Phase FMC) |
| Eye relief |
20mm |
| Barrel diameter |
2″ / 1.25″ |
| Camera threads |
M54, M43 |
| Modular design |
Yes - converts to 6-element 2″ Erfle eyepiece |
| Eyecup |
Rubber fold-down |
Summary
- Wide 68° field of view with sharp, colour-accurate images
- Multi-layer FMC coating on all optical surfaces
- Modular design - works as two different eyepieces
- Built-in M54 and M43 threads for afocal photography
- Compatible with 2″ and 1.25″ focusers
- Comfortable 20mm eye relief for extended observing sessions
