For 30 years, Tele Vue has pushed the boundaries of APO refractors, as well as eyepieces, to the recognized pinnacle of performance. It was not surprising 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, 102i, 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 was 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. 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, Tele Vue 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. They 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 Tele Vue's 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 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 the Focusmaster Computer Interface.
- Type: APO (Nagler-Petzval) Refractor (Elements/Groups: 4/2)
- Objective: 101mm
- Focal Length: 540mm
- Focal Ratio: f/5.4
- Drawtube/Focuser: 2.4-inch, Focusmate dual-speed rack/pinion
- Length OTA: 25.5"
- Weight OTA: 10.65 lbs
- Maximum Visual Field: 4.9° (with 2-inch 55mm Plössl)
- Maximum Recommended Power: 250x
- Enlarged focuser with 3" entrance aperture and 2.4" exit aperture
- Focuser body has brass clamp ring with 2-lock knobs
- Accessory end-ring with tilt capability and 4-lock knobs
- Imaging insert threaded for Imaging System components
- 2" accessory insert for visual or other 2" accessories
- Focusmate dual-speed focuser 10:1
- Sliding metal dew shield
- Screw-on metal lens cover
- Hard-shell carry case