TS Optics UWAN 4mm 82° 1.25″ Eyepiece
The TS Optics UWAN 4mm eyepiece combines a short focal length with a surprisingly wide 82° apparent field of view. Standard planetary eyepieces give you a narrow slice of sky. The UWAN 4mm gives you space - a planet or globular cluster does not sit pressed against the centre of the field, but appears as part of a natural scene with its surroundings visible around it.
Wide-angle optics built for serious planetary work
The UWA optical design uses 7 elements in 4 groups, which delivers solid correction all the way to the edge of the field. This is where many wide-angle eyepieces struggle, but the UWAN 4mm maintains clean, well-corrected views across the full 82° field.
The barrel is filled with an inert gas. This prevents internal fogging when you move between different temperatures - a practical benefit during night sessions when the temperature drops quickly.
Comfortable to use - even with glasses
For a 4mm focal length, 12mm of eye relief is above average. You do not need to press your eye close to the eyepiece to see the full field. The fold-down eyecup lets you adjust the eye relief to suit whether you observe with or without glasses.
A built-in filter thread lets you attach standard planetary or narrowband filters directly to the eyepiece - no adapters needed.
Fits most telescopes straight away
The standard 1.25″ barrel fits the vast majority of telescopes available today. The eyepiece is 98mm tall with a 45mm barrel diameter and weighs 164g. It is a solid, well-balanced build that will not noticeably shift the balance point of your telescope when inserted.
Key specifications
| Parameter |
Value |
| Focal length |
4mm |
| Apparent field of view |
82° |
| Barrel size |
1.25″ |
| Optical design |
UWA, 7 elements in 4 groups |
| Eye relief |
12mm |
| Eyecup |
Fold-down, adjustable |
| Filter thread |
Yes, standard 1.25″ |
| Gas-filled body |
Yes, inert gas |
| Height |
98mm |
| Barrel diameter |
45mm |
| Weight |
164g |
Who is this eyepiece for?
The TS Optics UWAN 4mm suits observers who want high magnification without giving up field of view. It works well for planetary detail, globular clusters, and any object where you want both close-up power and a sense of the surrounding sky. The comfortable eye relief and adjustable eyecup make it a practical choice for extended observing sessions.
What can you expect to see?
- Fine surface detail on planets such as Jupiter, Saturn, and Mars
- Resolved stars across globular clusters
- A wider, more natural view than a standard planetary eyepiece at the same magnification
- Clean, well-corrected images from centre to edge
Typical magnification examples
The magnification you get depends on your telescope's focal length. Divide your telescope's focal length by 4 to find the magnification this eyepiece will give you. For example, a telescope with a 1,000mm focal length gives 250x magnification with this eyepiece.
