| This 9mm Vixen Lanthanum eyepiece uses seven optical elements in four groups to achieve an exceptionally long and eyeglass-friendly 20mm of eye relief. The 9mm Vixen eyepiece is designed for unvignetted medium to medium high magnification viewing with short focal length refractors and fast focal ratio/short focal length reflectors. It is starting to get into the range of being more or less regularly useful with long focal length refractors, reflectors, or catadioptric scopes (Schmidt- and Maksutov-Cassegrains) under good seeing conditions. While this eyepiece can perform well with these long focal length/long focal ratio scopes, don’t expect it to do so every night. Merely average seeing conditions (the kind you’ll experience most nights) can still limit its performance. The optical performance and width of field are quite good for a short focal length eyepiece, on a par with that of a good Plössl. There is a slight loss of contrast when compared to a Plössl, however, due to the additional optical elements needed to achieve the long eye relief of this Vixen. The loss is minimal though, and this Vixen still has the benefit of much longer and more comfortable eye relief at a cost half that of other 20mm eye relief eyepieces. |
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