Never one to rest, Tele Vue took the opportunity to tweak the scope in small but meaningful ways. Both the optical and mechanical designs have been revised to reduce atmospheric defocusing sensitivity (visually the difference is virtually indiscernible). The new lens prescription delivers smaller spot sizes over a broader wavelength range than previously, while a new stainless steel front cell helps provide better thermal stability in extreme climates. Advanced multi-coatings are applied to maximize contrast and transmission. Still the fastest in the industry, there is just no competitive comparison considering its f/5.2 speed and flat-field.
The instrument has also been mechanically updated from its longer captive dew shield to its new 10:1 focuser pinion assembly, made for Tele Vue by Starlight Instruments. Along with an all new gloss black anodized metalwork treatment, the handsome new shapes of the dew shield and rear cell bring a refined elegance to this high performance APO refractor.
The non-vignetting focuser retains its 3" input and 2.4" output to reduce bulk and permits imaging across the largest commercially available CCD chips (52mm diagonal). No need for a heavier, more cumbersome 3" focuser. Every 2.4" focuser we make is tested to hold and drive a minimum of 6 lbs of weight in vertical orientation.
Except for a new Focusmate Driver attachment (available shortly), all other Imaging System accessories fit as previously.
Just what makes the TeleVue NP-127is so special? The standard by which it is built. The four-element air-spaced Nagler-Petzval system begins with a precision machined 660mm focal length optical tube that's fully internally blackened to prevent any stray light inflections. Then it's combined with a 127mm aperture extra low dispersion glass doublet as the primary lens with a with a secondary field-flattening/aberration-correcting extra low dispersion glass doublet at the opposite end. All optical surfaces receive index matched multi-coatings. This design offers up diffraction-limited apochromatic peformance - simultaneously correcting for field curvature, astigmatism, spherical aberration, coma, secondary spectrum and spherochromatism.
Televue was determined to make the NP127is 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 Televue-60is to the new NP101is and NP127is and then going beyond. The NP101 (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 52mm 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.