Tele Vue NP101is APO Refractor Telescope

Tele Vue-NP101is

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.

The NP101 (540mm, f/5.4, 4") maintains its optical specifications yet with a redesigned 4-element optical system. Larger rear lens groups absolutely minimize vignetting in formats up to 50mm diagonal. For these large chips, an optional field corrector was developed 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 more than 5kg 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 drawtube has four 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.

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". The Focusmate Driver can be remotely computer-controlled with Focusmaster Computer Interface.

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.