This is a very good medium power eyepiece for lunar observing, resolving globular clusters, picking up detail in emission and reflection nebulas, etc. It has a rubber grip ring for a comfortable grip in cold weather. The 20mm is supplied as the standard equipment eyepiece with TeleVue refractors up to $3595 in price, giving you some idea of its quality. (You don't think TeleVue would risk killing a $3595 sale by putting in anything less than a superb eyepiece, do you?)
It provides an almost 4.5mm exit pupil with an f/4.5 Dobsonian reflector for rich field scanning of the Milky Way star clouds in Sagittarius. It's an excellent choice to complement the 40mm eyepiece provided with some go-to Schmidt-Cassegrains. It has a somewhat short eye relief that will limit the field for eyeglass wearers. Those who must wear eyeglasses while observing due to severe astigmatism would probably be better off using a Barlow and a longer focal length eyepiece with longer eye relief to reach this focal length, rather than buying this eyepiece for use on its own.
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