What makes the Tele Vue NP101is a "flat field" refractor?
The NP101is uses a 4-element Nagler-Petzval optical design. Many doublet and triplet refractors need a separate field flattener for imaging. In the Nagler-Petzval layout, a rear doublet widely spaced from the front doublet is part of the objective itself and flattens the field. Tele Vue only adds the LCL-1069 corrector for 35mm and larger formats or pixels under 6µm.
Can I use the NP101is for visual astronomy, or is it just for imaging?
It is a full visual instrument as well as an imager. Its fast f/5.4 focal ratio and 101mm aperture deliver bright, wide-field views of large deep-sky objects. With a 2" 55mm Plössl eyepiece, you reach a 4.9° true field. At the same time, its 1.1 arc-second resolution and color correction hold up on planets and double stars at high power.
What kind of mount do I need for the Tele Vue NP101is?
The optical tube weighs 10.7 lbs. For alt-az use, the Gibraltar-HD or Gibraltar5-HD are recommended for their sturdy legs, with the RS4-8004 ring. For imaging, the MRS-4011 dual ring set is best suited, and Tele Vue makes adapter plates for popular German equatorial mounts; size the mount for the tube plus your camera train.
How does the optional 0.8x reducer (NPR-2073) change the NP101is's performance?
The NPR-2073 reducer converts the NP101is into a faster, wider imaging system. It changes the telescope's specifications from 540mm at f/5.4 to 432mm at f/4.3. This 25% wider field of view is ideal for capturing large nebulae like the North American Nebula (NGC 7000) or the Andromeda Galaxy (M31) on a full-frame sensor, and f/4.3 needs about 64% of the exposure time of f/5.4 for the same signal on extended objects.
What is the purpose of the focuser's tilt adjustment on the NP101is?
The end ring is pre-set parallel to the focal plane. If your images show tilt, find the part of the field that reaches focus first when racking out, loosen the three jam screws, jack the end ring out to match it (a quarter turn moves 198 microns), then lock it. Make these adjustments during an imaging session, by trial and error.
Do I need extension tubes to reach focus with the NP101is?
For visual use with a standard 2" diagonal, the NP101is will reach focus with all Tele Vue eyepieces without any extensions. For imaging, it depends on your specific camera and accessories. The manual recommends threaded extension spacers that limit drawtube extension to about 0.75" (20mm). You will need to calculate the required spacing based on your camera's back-focus distance.
What is the best eyepiece for viewing the Orion Nebula (M42) with the NP101is?
To frame the entire Orion Nebula complex, from the Trapezium core to the fainter outer loops, a wide-field, low-power eyepiece is best. A Tele Vue 27mm Panoptic would yield 20x magnification and a 3.2° true field, easily containing the nebula. For a more immersive "spacewalk" view, a 17mm Ethos would provide 32x and a 3.1° field, darkening the sky background and enhancing contrast on the faint nebulosity.
Does the NP101is require collimation?
No user collimation is needed. The front doublet is aligned at the factory with three alignment screws that you should never touch; contact Tele Vue if the scope ever needs re-collimation.
Is the included hard case suitable for airline travel?
The custom hard-shell case is built for carrying and storage: the telescope in its case weighs 19 lbs. Always keep the two accessory bags in the lid when carrying, because they hold the telescope down; Tele Vue does not state airline suitability.
How does the focuser hold 12 lbs without slipping?
Each focuser is tested to hold 12 lb without flex. Two tension screws on top of the focuser body press on a brass clamp ring, which cinches down on the drawtube's Teflon sleeve. This allows you to add significant resistance to prevent slipping under heavy loads, and even when tight, the knobs, including the 10:1 Focusmate, can still drive the draw tube. Tighten the two screws in unison to avoid focus shift.
