| This Nikon zoom eyepiece is supplied as standard equipment with the 50mm Nikon Fieldscopes. It is also a very popular eyepiece with those who own an older Nikon Fieldscope body – either as a replacement for a lost or damaged zoom, or as a zoom for those who only bought a single magnification eyepiece or eyepieces when they bought their scope originally. The zoom provides magnifications of 13-30x with a 50mm Fieldscope, 20-45x with a 60mm Fieldscope, and 25-56x with an 82mm Fieldscope (or older 78mm model). A power ring on the eyepiece barrel allows quick magnification changes. The power ring is marked with the minimum and maximum magnifications for both the 60mm and 78/82mm Fieldscopes, with one intermediate power also marked for each size. As with any zoom eyepiece, the precise focal length or magnification of the Nikon zoom at any given point in time is not all that important. The experienced observer invariably adjusts the zoom magnification to match the seeing conditions and object size as he looks through the eyepiece, rather than first setting the zoom to an arbitrary focal length value according to the scale on the side of the eyepiece and using it at that power no matter what the seeing conditions. The flexibility of a zoom to instantly match the magnification to changing lighting or seeing conditions is one of the zoom eyepiece’s chief advantages. Match that flexibility to Nikon-grade optics and you have an exceptional tool for any birder.
The eyepiece threads into place in seconds. A separate locking ring at the base of the eyepiece allows the user to orient the eyepiece so that the power indicator mark is at the most convenient location, then lock the eyepiece into place so that it does not rotate accidentally when the power ring is turned. To prevent accidental loss in the field, a rubber O-ring at the base of the eyepiece threads compresses as the locking ring is tightened. This locks the eyepiece in place to keep it from turning or loosening during use. The O-ring also seals the scope against the entrance of dust and moisture. A soft roll-down rubber eyecup is standard. Roll it up for use without eyeglasses; roll it back down for eyeglass use.
With a 50mm Fieldscope . . .
The zoom at 13x has a 157' field at 1000 yards and 12.9mm eye relief.
At 20x it has a 115' field and 11mm eye relief.
At 30x it has a 92’ field and 11mm eye relief.
With a 60mm Fieldscope . . .
The zoom at 20x has a 105' field at 1000 yards and 12.9mm eye relief.
At 30x it has a 77' field and 11mm eye relief.
At 45x it has a 62’ field and 11mm eye relief.
With a 78mm or 82mm Fieldscope . . .
The zoom at 25x has an 84' field at 1000 yards and 12.9mm eye relief.
At 38x it has a 62' field and 11mm eye relief.
At 56x it has a 50’ field and 11mm eye relief.
The specified eye relief of 12.9mm at low power will show some vignetting for many eyeglass wearers. While the 12.9mm measurement is technically correct, the actual usable eye relief typically measures somewhat less due to the recessing of the eyepiece lens to protect it from being scratched accidentally when the eyecup is in the down position for eyeglass use. A somewhat shorter eye relief than specified is typical of all spotting scope eyepieces.
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