Focal length: 20mm
Barrel Diameter: 31.7mm (1.25″)
Apparent Field: 50°
Eye relief: 14mm
Field Stop Diameter: 17.1mm
Review This is a very good medium power eyepiece for lunar observing, resolving globular clusters, picking up detail in emission and reflection nebulas, etc.
The rubber grip give sure grip and makes it comfortable to use in cold weather.
The comfortable 14mm eye-relief is suitable for those wearing glasses .
Like all TeleVue Plossls it has filter threads to fit your filters and blackened lens edges as well as being parfocal.