Premium Refractors: Having It All
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Excerpts from Premium Refractors: Having It All review of Tele Vue NP-101 by Alan Dyer, from May 2002 issue of Sky & Telescope magazine
Nagler's latest entry in the premium-refractor market is the NP 101. Like some previous Tele Vue refractors, the NP 101 is a four-element design with a full-aperture doublet objective up front and subaperture doublet near the back. . . . While a field flattener is an add-on accessory with some apos, with the NP 101 a flat field is an integral part of the design, and the scope delivers pinpoint star images across wide-field eyepiece views and on 35-mm film. . . . As I discovered at first glance through its optics, the NP 101 improves upon the now-discontinued Tele Vue-101 and Genesis models by completely eliminating chromatic aberration. And it achieves this ultimate level of apochromatic performance in a tube about 6 inches shorter than those earlier models.
Fitted with Tele Vue's remarkable 31-mm Nagler eyepiece, the NP 101 showed pinpoint stars across a vast 4½° field. . . . This is a great combination for panoramic 'rich-field' views of the Milky Way.
Great optics are easy to evaluate — the NP 101 showed no sign of any aberrations, period. End of review! But to elaborate -- under a star test at high power I saw no color, no astigmatism, no spherical aberration, not even any asymmetry in extrafocal patterns from sphero-chromatism. Bright stars appeared as clean, white disks right through focus, with no magenta or cyan fringing inside or outside of focus. In focus, stars appeared as tight, sharp Airy disks, surrounded by a subtle inner diffraction ring and no spurious fuzz — a textbook-perfect pattern.
Saturn appeared etched into a dark sky. Differences in ring shading were obvious, as were several of the planet's faint moons. Jupiter's disk looked clean white with no discoloration from unfocused wavelengths or filtering effect of glass or coatings. Here was pure unadulterated light, just what an apo refractor should deliver.
The tube's internal blackening worked well. Low-power views showed no sign of flares or ghost images from bright objects just outside the field. This is clearly one of the world's best telescopes, able to match or exceed the performance of any other premium apo of this aperture.
Tele Vue NP 101 is a no-compromise design that performs well for all visual and photographic purposes. It can cruise effortlessly from superwide-angle scenes to high-resolution planetary views. Although it carries a premium price, the NP 101 may be all the telescope many observers ever want.
— Dyer, A. "Premium Refractors: Having It All." Sky & Telescope. (May 2002): 50, 51.