Tele Vue NP101Is 4" f/5.4 Nagler-Petzval apochromatic refractor

The Backyard Astronomer's Guide said of the original TeleVue NP101, "optics don't get any better than this;" while Sky & Telescope gave the NP101 top honors (May and June 2002) and selected it as the test instrument for its landmark review of the SBIG STL11000 CCD camera (July 2004). Featuring a new enlarged 2.4" focuser and redesigned optics, this new TeleVue NP101is (Imaging System) improves and extends the photographic capability of the original NP101.

The new TeleVue NP101is sets new optical and mechanical quality standards in a moderately small and highly portable apochromatic refractor for the serious observer and astrophotographer. TeleVue first reinterpreted the incredible design flexibility of the time-proven Petzval portrait lens into an astronomical objective over 20 years ago. They've been refining the design ever since. Nagler-Petzval optics permit the optical designer greater freedom to simultaneously correct for coma, astigmatism, field curvature, secondary spectrum, spherical aberration, and spherochromatism than any other commercial optical design.

This newest 4" four-element air-spaced Nagler-Petzval system has a 101mm aperture ED doublet at the front of the scope, with a second field-flattening/aberration-correcting ED doublet at the rear. This combination of materials and design gives the TeleVue NP101is diffraction-limited apochromatic (spurious color-free) performance across the entire visual spectrum. In addition to exceptional visual performance, both inside the solar system and beyond, it has been optimized for deep space imaging, particularly with CCD cameras having large format detector chips with diagonals up to 50mm across. Every optical and mechanical element has been optimized to work as a single integrated unit, with new features to make imaging easier and more flexible.

For visual use, the scope's 540mm focal length is long enough, using a 1.25" TeleVue 2.5mm Nagler eyepiece, to provide 216x for high magnification observations of the Moon, planets, and binary stars; yet it will also produce a huge 4.1° field at 15x, using a 2" TeleVue 35mm Panoptic eyepiece for wide field observing.

Its image quality, easy set-up, and airline portability make it a scope you will use often. Manufacturing advances in lens finishing, including interferometric monitoring of all surfaces, and TeleVue's stringent made-in-the-USA telescope assembly and quality control, insure uniformly excellent results with every telescope, and a level of manufacturer-direct service that's all too rare.

Whether you are interested in terrestrial nature studies, astronomical rich-field or planetary observing, or photography of the earth and skies, just put in an optional star diagonal and eyepiece or attach a camera and the TeleVue NP101is will satisfy your observing desires right out of its case.

This Telescope's Optical and Mechanical Systems . . .

Nagler-Petzval apochromatic refractor optics: 4" (101mm) aperture, 540mm focal length, f/5.4 apochromatic four-element air-spaced optical system. ED (Extra-low Dispersion) glass elements in both the front and rear doublets of the system provide images that are free from spurious color and other optical aberrations.

The newly-redesigned optics feature a field-flattening rear lens group that is larger than that in the original - and still available - NP101. The larger second optics group minimizes vignetting in photographic formats having up to a 50mm diagonal. In addition, for CCD cameras using a detector chip with a 35mm or larger diagonal, an optional large field corrector is available so that the stars in the newly brightened non-vignetted corners of the image are virtually as tightly-focused and sharp as those in the center of the field. 

The new front lens cell is made of stainless steel. This provides better thermal stability in extremes of heat and cold and when taking your scope from a warm house outdoors to observe on a cold winter's night.

Multicoated optics: Fully coated on all surfaces with multiple layers of antireflection materials for high light transmission and good contrast.

Dual-speed rack and pinion focuser: The newly-designed focuser has a non-vignetting internally-tapered drawtube with a 3" entrance aperture and a 2.4" exit aperture. This tapered design prevents any restriction of the larger converging light cone from the scope's larger field-flattening rear lens group. The drawtube terminates in an end ring that has a tilt capability to correct for any residual focal plane tilt. This is particularly important with the more stringent focus requirements of CCD cameras. Four lock knobs on the end ring hold the supplied 2" accessory adapters firmly in place with no possibility of tilting under the weight of camera or accessories. The end ring also accepts a "position stop" for an optional digital micrometer that allows repeatable focus measurements with a 0.0001" accuracy.

The imaging adapter is threaded to accept TeleVue's new Imaging System accessories - including large diameter extension tubes, optical accessories, and camera and CCD attachments, all with mating threads. The separate visual adapter has a 2" non-marring brass clamp ring with two lock knobs to hold a 2" star diagonal or other visual accessories firmly in place.

Fine focus system: The focuser is equipped with a Focusmate 10:1 reduction ratio dual-speed fine focus system on the right focus knob. This precision focuser is made for TeleVue by Starlight Instruments, makers of ultra-premium Feather Touch focusers.While the left focus knob still provides TeleVue's standard focusing speed, the Starlight Instruments Focusmate on the right knob provides extremely sensitive 10:1 ratio fine focusing for imaging. Focus changes are measurable with an optional Digital Micrometer Kit to better than 1/10,000" for precisely repeatable focusing. Both the standard focus and the Focusmate use large knurled focus knobs that are easy to operate, even while wearing gloves or mittens in cold weather.

An optional Focusmate Driver permits pushbutton electronic motor control of the focusing process. The Focusmate Driver has directional pushbuttons and adjustable speed. A tap on a pushbutton permits vibration-free focusing in steps as small as approximately 0.0005". The Focusmate Driver can be remotely computer controlled with software under development.

Optional photographic accessories: Optional photo accessories include the following: a Digital Indicator Kit for digital readout of the focuser position for repeatable focus points; a Focusmate Driver electronic vari-speed motor control for the Focusmate fine focus mechanism; a Large Field Corrector for optimized edge performance with large diagonal CCD chips; extension tubes of various lengths to bring various CCD and 35mm cameras to focus; an adapter to connect the SBIG STL11000 CCD camera; an adapter to connect a standard 35mm camera using a T-Ring; an adapter to connect a Canon EOS or digital SLR using a wide mouth Canon T-Ring; and a 0.8x focal reducer for wider field imaging.

Sliding captive dew shield: The new, longer retractable dew shield slows the formation of dew on the lens to extend your undisturbed observing time. The longer dew shield also improves visual and photographic contrast by shielding the lens from off-axis ambient light (the neighbor's yard light, moonlight, etc.) For transport, the retractable lens shade keeps the overall length of the optical tube to a manageable 25.5" when it is retracted.

Mounting rings: No mounting rings are supplied for the 101mm diameter optical tube. The optional TeleVue #MRS4 dual 4" mounting ring set is designed specifically for installing the NP101is on wide variety of equatorial mounts and mounting adapters.

Finderscope mounting point: No finderscope is supplied. However, dovetail accessory mounting slots for a finderscope and other accessories (such as a piggyback camera mount) are provided on the optional TeleVue #MRS4 dual mounting ring set.

Carrying case: A custom foam-fitted locking hard shell case is standard. The case has a large accessory compartment built into its lid.

• Lens shade
• Dust cover
• Hard case
• Visual adapter ring
• Imaging adapter ring