Tele Vue-NP101is Telescopes > Tele Vue-NP101is > Development

For 30 years, Tele Vue has pushed the boundaries of APO refractors, as well as eyepieces, to the recognized pinnacle of performance. We were gratified but not surprised that Backyard Astronomer's Guide said of the NP101: "optics don't get any better than this." No wonder Sky and Telescope rated the NP101 tops and selected it as the test instrument for its landmark review of the SBIG STL11000 CCD camera . The "is" versions of the Tele Vue-60, NP101, and NP127 retain the exemplary wide field and planetary visual capability while adding new features to make imaging easier and more flexible.

Tele Vue-NP101is
Tele Vue-NP127is

We were determined to make the NP series optically, mechanically, and functionally as perfect as possible for imaging up to 50mm diagonal chips without penalty to its near ideal visual operation. (Reviewer Note.) How? By applying the developments created for the Tele Vue-60is to the new NP101is and NP127is and then going beyond.

Imaging System scope...
Imaging System scope with DSLR camera on Vixen Sphinx mount. Accessories shown include Focusmate Driver and Digital Indicator Kit.

The NP101 (540mm, f/5.4, 4") and NP127 (660mm, f/5.2, 5") maintain their optical specifications yet with redesigned 4-element optical systems. Larger rear lens groups absolutely minimize vignetting in formats up to 50mm diagonal. For these large chips an optional field corrector was developed (Reviewer Note.) so the corners of the newly brightened edges would virtually be as perfect as the center of the field.

Next, to take full advantage of the larger lenses, we developed a larger focuser and draw tube having a 3" front aperture and 2.4" rear aperture. This eliminates any restriction of the larger diameter converging light cone. We build and test the rack and pinion focuser to hold 12 lbs. of weight, yet still permit extremely fine focusing control via a 10:1 dual speed pinion assembly. This new draw tube also permits quick change from visual to imaging operation and allows full camera rotation without focus change. In addition, it has the capability to correct for any residual focal plane tilt and accepts a "position stop" for our digital micrometer to allow repeatable focus measurement to 0.0001".

To maintain squareness to the optical axis while changing camera orientation, the draw tube has three lock screws that tighten against a taper on the "imaging insert" ring. This insert is threaded to accept Tele Vue's new Imaging System accessories including large diameter extension tubes, optical accessories, and camera and CCD attachments, all with mating threads. (Reviewer Note.)

The Focusmate 10:1 planetary ball type reduction focuser provides extremely sensitive focus adjustment, measurable with the optional Digital Micrometer Kit to better than 1/10,000". Also, the optional Focusmate Driver permits electronic motor control of the focusing process. The Focusmate Driver has direction push-buttons and adjustable speed. A tap on the button permits vibration-free focusing in steps as small as approximately 0.0005".

Tele Vue has been known for producing visual instruments "even better than you imagined." We aim to achieve the same with our imaging equipment. Our dedicated local machinists and in-house staff are as committed as ever to deliver on these quality and performance goals. (Reviewer Note.)

Related Links

Tele Vue-NP101is Operating Guide
Tele Vue-NP127is Operating Guide
Tele Vue Eyepieces for Tele Vue Refractors
Tele Vue APO Design and Build 'Secrets' (blog post)

Tele Vue set about addressing the concerns of high-end astrophotographers when it designed the "is" line. I feel the company exceeded its goals.

— Di Cicco, Dennis, "Tele Vue’s Flagship Imaging System." Sky & Telescope, July 2007

There's no accolade I can offer about the visual performance of the TV-NP127is that others haven't already bestowed on it. The scope has it all: high-contrast, color-free, textbook-perfect images spread across a remarkably flat field. The Moon , planets, double stars, and bright deep-sky objects are all rendered exquisitely in the eyepiece.

If you expect better from a 5-inch f/5 refractor, you probably haven't been living on this planet.

— Di Cicco, Dennis, "Tele Vue’s Flagship Imaging System." Sky & Telescope, July 2007

The scope also performs superbly for imaging. Fitted with the Large Field Corrector (the only way I tested the scope), the TV-NP127is delivers pinpoint stars across a field the size of a 35-mm film frame with only a little more than 10% light drop due to vignetting at the edge of the frame's long axis.

Just as stars visually snap into focus with quality optics, I found it easy to tell when the TV-NP127is was in perfect focus for imaging. The faintest stars appeared as mere pinpricks, and brighter ones were sharply defined dots. Indeed, star images were so crisp that my colleague Sean Walker and I would hunt for tiny galaxies in wide-field images by looking for "stars" that were ever-so-slightly fuzzy.

I saw no focus shift when switching between standard red, green, and blue filters used for conventional tricolor imaging -- a tribute to the TV-NP127is's superb color correction.

— Di Cicco, Dennis, "Tele Vue’s Flagship Imaging System." Sky & Telescope, July 2007

The TV-NP127is has all the mechanical hallmarks of previous Tele Vue refractors: solid, well made, and beautifully finished.

Tele Vue's inclusion of a tilt adjustment on its focuser shows an unusual level of commitment to making the "is" scopes imaging friendly.

— Di Cicco, Dennis, "Tele Vue’s Flagship Imaging System." Sky & Telescope, July 2007

There's no such thing as an all-purpose optical system for astrophotography, but if you're looking for a 5-inch f/5.2 refractor that can cover today's 37-mm-square CCDs, then you'll be hard pressed to do better than the TV-NP127is.

— Di Cicco, Dennis, "Tele Vue’s Flagship Imaging System." Sky & Telescope, July 2007

Accessorized Telescopes on Tele Vue Mounts
TV-NP101is telescope outfitted with Starbeam unit-power finder, and 10mm Delos eyepiece. Gibraltar-HD4 Mount and Eyepiece Caddy set.

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