Omegon Premium Flatfield 15.5mm 65° Eyepiece (1.25 inch): flat field of view with ED optics
The Omegon Premium Flatfield 15.5mm delivers on its name: a flat field of view where stars remain point-like even at the edges. The middle focal length of the series, with a wider 65-degree field.
The series corrects the field curvature that makes most eyepieces blurry at the edge, and the ED lens element keeps the color reproduction pure. Even on fast Newtons around f/5, the edge remains sharp.




Flat field, high contrast
The optical construction with an ED element and multi-layer coating on all air-to-glass transitions delivers a sharp image with high contrast. Objects that drift to the edge retain their shape and sharpness.
Pleasant insight, parfocal series
With an interpupillary distance of 16 mm, you can observe relaxedly, without black shadows if your eye is slightly off-axis. The series is parfocal: changing the focal length requires hardly any refocusing.
The 1.25-inch barrel has filter threads for moon and color filters.
What do you see with 15.5 mm?
On a 150/750 Newtonian, 15.5 mm gives a magnification of 48x, and at a focal length of 1200 mm, it's 77x. The moon with its surroundings, double stars, and bright nebulae are rewarding targets.
The flat field also makes this focal reducer strong for open star clusters: each star remains a point.
Featured accessories
The Premium Flatfield series ranges from 5.5 to 25mm and is parfocal: two or three focal lengths form a complete set. An Omegon moon filter (1.25 inch) dims the bright moon image at longer focal lengths.
For whom yes and for whom no
- ✓ Observers with fast telescopes (f/5) who value edge sharpness
- ✓ To see stars as pinpoints to the edge instead of smeared
- ✓ Owners of multiple focal planes in the series: parfocal switching
- For those seeking the widest field of view: the SWA and Redline series offer 70 degrees
- ✗ Smart telescopes without interchangeable eyepieces
Specifications
| Focal length | 15.5 mm |
| Apparent field of view | 65 degrees |
| Eye relief | 16 mm |
| Optical design | Flat field with ED lens element, multi-layer coated |
| Mount | 1.25 inch (31.7 mm), with filter thread |
| Special feature | parfocal within the series, flat field of view up to f/5 |
| Series | Omegon Premium Flatfield |
You can find more accessories for this merk at the Omegon merk Page.









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