TeleVue NP101is APO Refractor Imaging System

TeleVue NP101is APO Refractor Imaging System

Concept: CCD cameras have challenged telescope optics beyond anything ever placed at the focal plane. I knew our APO objectives were up to the Tele Vue challenge, and with the proper tweaks would be extraordinary tools for the imager. With Tele Vue Imaging System ("is") telescopes, we have refined our instruments and optional equipment beyond anything a CCD chip has seen. We started small (literally) in 2005 with the Tele Vue-60is and available Digital Micrometer Kit. Achieving critical acclaim with the 60is, we were encouraged to further develop "is" telescopes and accessories to maximize aperture, real field coverage and performance, and to make the processes easier for the imager. - Al Nagler

For 25 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 (May & June 2002) and selected it as the test instrument for its landmark review of the SBIG STL11000 CCD camera (July 2004). 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.

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. 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") 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.

In order to take full advantage of the larger lenses, a non-vignetting focuser was developed to prevent any restriction of the larger converging light cone. The draw tube has a 3" front aperture and 2.4" rear aperture. 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 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.