| This Nikon wide power range zoom eyepiece is supplied as standard equipment with the 60mm and 82mm 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 wide magnification ranges of 13-40x with a 50mm Fieldscope, 20-60x with a 60mm Fieldscope, and 25-75x with an 82mm Fieldscope (or older 78mm model). Keep in mind that the highest magnifications with each of these scopes have very small exit pupils in the 1mm size (1/25th of an inch) range. Such small exit pupils require brightly lit observing conditions to reveal the fully saturated colors that bring out all the performance of which the scopes are capable. For average seeing conditions, you’ll probably find that using somewhat less than the maximum magnification possible will provide the most consistently satisfying images.
A power ring on the eyepiece barrel allows quick magnification changes. The power ring is marked with the minimum and maximum magnifications for all three scope sizes – 50mm, 60mm, and 78/82mm. Intermediate powers are not marked. 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 marks are 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 twist-up rubber eyecup is standard. Twist up for use without eyeglasses; twist back down for eyeglass use.
With a 50mm Fieldscope . . .
The zoom at 13x has a 157' field at 1000 yards and 14.1mm eye relief.
At 25x it has a 91' field and 12mm eye relief.
At 40x it has a 69’ field and 11mm eye relief.
With a 60mm Fieldscope . . .
The zoom at 20x has a 105' field at 1000 yards and 14.1mm eye relief.
At 40x it has a 61' field and 12mm eye relief.
At 60x it has a 52’ field and 12mm eye relief.
With a 78mm or 82mm Fieldscope . . .
The zoom at 25x has an 84' field at 1000 yards and 14.1mm eye relief.
At 50x it has a 49' field and 12mm eye relief.
At 75x it has a 42’ field and 12mm eye relief.
The specified eye relief of 14.1mm at low power will show some vignetting for many eyeglass wearers. While the 14.1mm 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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