Binorum Advanced 20mm 66° FMC 1.25″ Eyepiece

Binorum Advanced 20mm 66° FMC 1.25″ Eyepiece

A 20mm eyepiece with a 66° field of view is one of the most versatile choices for astronomical observation. Used with telescopes of standard focal lengths, it delivers a wide, open view of star clusters, nebulae and larger planetary objects. This wide-angle SWA eyepiece with a 1.25″ barrel fits the vast majority of telescopes on the market - no adapters or reducers required. The combination of a longer focal length and a wide field of view makes it an excellent tool for sweeping the night sky.

Comfortable viewing - even with glasses

The 17mm eye relief lets you position your eye comfortably without pressing close to the lens. You can relax and focus fully on the object you are observing. This is especially welcome during longer sessions on cold nights, when every bit of comfort matters. The eye relief is also sufficient for spectacle wearers, who often struggle with restricted field of view or awkward head position when using shorter eyepieces. The SWA (Super Wide Angle) optical design minimises distortion at the edges of the field and keeps the image sharp right to the edge.

FMC coatings for sharp, high-contrast images

Fully multi-coated (FMC) optics on every optical surface significantly reduce reflections and suppress stray light that would otherwise lower image contrast. In practice, this means that even faint objects - subtle detail in nebulae or stars near the edge of the field - remain clearly visible rather than washing out in unwanted scatter. FMC coating is today's standard for quality astronomical optics, and its presence on every lens surface - not just the outer ones - ensures consistent image quality throughout. The resulting image looks natural, with no yellow or blue cast that is typical of lower-quality coatings.

Ideal for beginners and experienced observers alike

The Binorum Advanced 20mm suits beginners looking for their first quality accessory as well as experienced observers who want a reliable eyepiece for wide-field surveys. It works with refractors, reflectors and catadioptric telescopes alike - the standard 1.25″ barrel makes it compatible with almost every telescope available. This survey eyepiece with a 20mm focal length is the natural starting point at the beginning of an observing session, when you need to locate the right area of sky before switching to a higher-magnification eyepiece. Simply put, this will become one of the most-used eyepieces in any collection.

About Binorum

Binorum is a Czech brand founded by active astronomers who know exactly what an observer needs in the field. The brand's philosophy is straightforward - astronomical optics and accessories should be high quality, affordable and designed with real observing conditions in mind. The Binorum range covers a wide variety of products, from eyepieces and filters to observing accessories, so you can build a complete setup from one trusted source. Every product goes through careful selection and testing, meeting the standards that its creators - as astronomers themselves - apply to their own optics on every clear night.

Technical specifications