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NP101 - f5.4 Nagler Petzval Apochromat Refractor (4.0" aperture)
Introduced in 2001, this was replaced in April 2011 by the improved TeleVue NP101 with Feather Touch®
This is among the finest 4 inch Apo refractors sold by Company Seven! While most other manufacturers have missed the boat on making a 10 cm Apo easily portable, or require their instrument be disassembled for travel, TeleVue NP101's claim to fame (in addition to its superb optical properties) is that it is so compact and lightweight that it can be carried on as baggage to a commercial airplane. Although the airlines often employ a template limiting packages to about 22 inches, this 26 inch long telescope in its narrow optional carrying bag will usually be permitted onto an airplane. This brings the number to only TWO four inch Apos that that Company Seven offers which afford this degree of transportability.
DEVELOPMENTCompared to the other popular telescope designs (reflecting and Catadioptric) the well made refracting telescopes will offer the most natural, high contrast, three dimensional views of the brighter objects; these have certainly have been the choice of professional visual astronomers. The 4 and 5 inch aperture telescopes pioneered by TeleVue proved the concept of using a refractor for deep sky observing, and for imaging. If one could build a large enough mirror telescope to show what details a comparable refractor could show, then the field of view through the mirror systems would be relatively narrow. However, most refracting telescopes up to the early 1980's were relatively high magnification instruments affording relatively narrow fields of view. Optical glass (and crystal) design innovations of the 1980's resulted in relatively fast consumer telescopes of f9 or so, compared to the previous typical f12 to f15 ratio Achromat this afforded wider fields of view better suited to deep sky observing. And shorter telescope tube weight less and can be managed on lighter weight and more compact mounts. Since the best apochromatic refractors such as the NP101 are the most difficult and costly in raw materials to make consistently well, the Apo refracting telescope will cost notably more than competing designs - but the waiting lists and high resale values testify to the confidence that the astronomy community has in telescopes such as these.It was an original first generation TeleVue "Renaissance" telescope (Serial No. 1019) evaluated in the March 1985 issue of "Modern Photography" magazine that earned "excellent" ratings on resolution tests, and "High" ratings for contrast with praise that included "with image quality beyond ordinary camera lens". Knowing the new NP101 reflects dramatic improvements in the state of lens making technology, we can only wonder how such a modern telescope might be reviewed. And to our surprise in 1986 "Audubon" magazine rated the original "Renaissance" as the top refracting telescope in a comparative survey of birding telescopes (the "Questar Field Model" a compact Maksutov-Cassegrain telescope was rated top choice over all); but we found it hard to believe that too many birders would haul a 4 inch Apo telescope very far - until the NP101 arrived. The "NP101" is a sixth generation TeleVue four element design. It follows the original TeleVue 5 inch "MPT" system introduced in 1982, the beautiful brass 4 inch aperture f5.5 "Renaissance" telescope introduced in 1984, the "Genesis" 4 inch f 5 telescope of 1988, and the "SDF" 4 inch f5.4 of 1993, and the "101" and "Renaissance 101" telescopes of 1996. Al Naglers patented four element designs are based on the original "Petzval" concept, this is an arrangement of refractive elements where a two element air spaced objective lens (housed at the front of the telescope) passes the light through to a second doublet lens positioned at the rear of the telescope and before the focuser. The doublet lens group usually functions to 1) reduce the effective focal length, and 2) reduce or eliminate curvature of field.
In prior TeleVue telescopes, one could remove the rear doublet lens and use the telescope with the objective lens alone in place. But the NP101 is a departure from traditional TeleVue Petzvals. Incorporating TeleVue's best 101 mm aperture air-spaced "SD" special dispersion doublet lens with what appears to be a simple doublet telecompressor/field flattener, the NP101 provides flat field wide angle views. But in fact this is a more complicated design where neither lens group can function independently without the other to form a good quality image. Accepting 1-1/4" or 2" accessories including the highly regarded TeleVue Radian, Nagler and Panoptic eyepieces, magnifications as low as 10X and a tack sharp field of view of as wide as 4.9 degrees are possible! A multi layer anti reflection coating process of the lenses, and on all the TeleVue eyepieces prevents light reflection off the surface of, or between the lenses. The result is a very fast, wide and flat-field system so well corrected that panoramic nature or star and planetary images are breathtaking. A collapsing lens shade aids portability. Its' uses include birding, video and film photography as well as astronomy. The TeleVue "NP101" telescopes introduced in August 2001 are the first large TeleVue Apochromatic refractors which Company Seven found to be truly competitive if not superior in optical and mechanical performance to the best 4 inch aperture Apos ever made. These provide false color-free, sharp, clear and high contrast images. The TeleVue NP101 also remains the worlds fastest, mechanically compact, flat field apochromatic 4 inch telescope.
PERFORMANCEThe objective lens of the NP101 is of an SD air spaced doublet design where two lenses (crown and flint) are matched to work as one; the positive element is of a fluorocrown substitute with special dispersion glass. In fact this design allows excellent color correction without annoying purple fringes (secondary color) or spherical aberration common to less sophisticated achromatic refractors, and better than a number of older triplet and modern doublet apochromat designs. A matched doublet lens group at the rear compensates for some design characteristics of the objective lens. The system provides a flat field, wide angle capability. Spherical correction is very good also with the air space of the objective contributing to this correction. Images of the stars and the planets are presented in their natural colors, daytime objects viewed at commonly used magnifications will appear quite three dimensional and sharp and contrasting.The system's eight air to glass surfaces have a multilayer antireflection coatings that improves overall light transmission across the visual wavelengths and from 400nm to well beyond 700nm. The coatings used on the NP101 telescope are in fact engineered to match the characteristics of each glass type and curve radii. This process virtually eliminates ghost images and flare and it improves color rendition. All of this achieves a dramatic increase in image contrast and actual light transmission, with a corresponding reduction in flare which might otherwise originate by internal reflections. Overall the complete four lens system provides about 180 times the light gathering power of the unaided human eye - about the same as typical doublet systems. On most nights, the settling down time for the optics are on the order of minutes: from room temperature to sub-freezing conditions it rarely requires more than 30 minutes to acclimate. The lenses are so well figured that the consistency between telescopes is quite good, and each is capable of operating at very high magnification cleanly (even with optional "Barlow" or "Powermate" lenses). This telescope crosses that threshold necessary to routinely obtain meaningful views of the planets, showing several bands and their shades of color (from creamy whites to beige, tan, browns) on Jupiter - observe the four largest moons of Jupiter and their shadows cast on the surface as distinct discs as they transit across the planet! Study the Cassini division and banding on Saturn, the polar cap and dark markings on a fiery red Mars. With an eyepiece that shows 1/2 degree field or so (such as a 5 or 6mm "Radian") take a walk on our apparently three dimensional Moon possibly resolving objects on the Moon as small as 4.4 km in diameter. Or follow its' terminator throughout the moon phases (a optional neutral density filter is suggested to tone down its brightness). With an optional white light solar filter (such as our Baader AstroSolar film) observe Faculae and Sunspots on the Sun! With our optional Hydrogen Alpha filters (either the DayStar ATM or University series) observe Faculae, Sunspots, the Peach-fuzz like photosphere on the Sun as well as the sheer curtain like Prominences as they erupt from the Sun out into the blackness of space!
With TeleVue's 2" focuser and a matched wide angle ocular the NP101 reveals its extraordinary wide field of view ability showing up to 4.88 degrees at 10X to reveal the entire "Messier Catalog" of deep sky wonders, or to be employed for panoramic viewing of a seashore or countryside. Imagine a telescope that at a dark sky site has the combination of resolving power and field of view to sweep the Milky Way, see the Double Cluster in Perseus (NGC-869), find the Andromeda galaxy (M-31) and see it's ellipsoid shape, and with no doubt see the distinct forms of large Nebulae such as the Veil and North American Nebulae! With a wide angle eyepiece the TeleVue 101 can reveal all three stars of Orion's belt, closer in it reveals the jewel like stars of the Trapezium - a birthplace of stars, with a sweeping wisps of greenish gas clouds surrounding it. With a higher magnification M13 (the Hercules star cluster) takes on a three dimensional "salt and pepper" appearance even from suburban skies on a clear night. By the time one finds a large enough aperture Catadioptric, reflecting, or achromatic refractor to see similar detail, then one can only see a fraction of their area due to the relatively high focal length of these competing telescopes; with other telescopes it would be something like trying to observe the night sky through a straw! In fact, one of the finest advertisements ever published for a telescope concept is the book Deep-Sky Companions: The Messier Objects where the author Stephen O'Meara sought to keep the drawings relevant to the amateur. To produce the highly detailed drawings of these celestial objects Stephen chose to observe with the second generation TeleVue "Genesis" telescope (4" aperture, 500mm f5) which as glass technologies advanced has since been replaced by the improved TeleVue apochromatic telescopes. This book has become one of our best advertisements for the versatile, readily transportable fast 4 inch (10cm) refracting telescopes. Similarly to keep things simple, and relate as much as possible to the average amateur observer Stephen chose to use the telescope on the simple but sturdy TeleVue "Gibraltar" alt-azimuth mount with Ash Wood tripod. He equipped the telescope with only a modest selection of accessories: TeleVue 22mm "Panoptic" eyepiece (providing 23X, 2.85 Degrees Actual Field of View), a original 7mm Nagler eyepiece (71X, 1.08 AFOV), and a TeleVue Barlow lens to increase the magnification by 1.8X. In fact Stephen O'Meara recently commented "the TeleVue NP101 would now be my telescope of choice". The NP101 compares favorably against many telescopes in field of view:
In fairness, the cost of the NP101 (equipped with either an optional Alt-Az or Equatorial mount) is positioned at a higher cost than most of the above telescopes. And as a practical matter for some applications in astronomy the nominal match of the "NP101" exit pupil to an average dark adapted human eye will be obtained at magnifications of between 17X and 15X. The best performance will be obtained at all magnifications if a wise choice of good quality oculars is made however, since the NP101 telescope incorporates a field flattening element then it is compatible with several of the simpler eyepiece designs. Again consider that an optional good quality "Barlow" or "TeleVue Powermate" amplifying (negative) lens, or optional long eye relief TeleVue "Radian" ocular (introduced in 1999) will usually be put into use to attain the highest usable magnifications which are necessary for observing small bright objects including planets, and close double stars. The NP101 telescope includes the TeleVue 2 inch "Everbrite" diagonal (or "zenith") mirror. The "Everbrite" mirror introduced in 1999 features a very high-tech dielectric coating (developed originally for military optics used in hostile environments such as blowing desert sand) which provide optimum performance and years of use. This TeleVue 2 inch diagonal has no aluminum or other reflective metal coating. Instead, the reflective surface consists of about 50 layers of thin film oxides similar to those used in anti-reflection coatings. The coatings are deposited by an electron beam evaporator at a high temperature. The result is that reflectivity is above 99% over the entire 4000 to 7000 Angstrom photo-visual range. Thin film coatings have extremely low surface scatter compared to aluminum or enhanced aluminum coatings; examination with a laser source shows approximately a five fold improvement in surface scatter. The mirror diagonal provides a comfortable viewing position for the observer by diverting the image at the rear of the telescope off axis by 90 degrees to the side, with minimal degradation of image quality. The view when using the telescope as it is provided will appear to be right side up, and is reversed left to right; this is not usually a problem for astronomy or nature observing because the image quality provided by the high quality mirror and 2 inch diameters panoramic oculars is exceptional. While Company Seven does offer optional 45 degree inclined image erecting prisms, these prisms can only accommodate 1.25 inch diameter oculars. Furthermore, the erecting prisms will not provide image quality to equal that of a good mirror diagonal; this is particularly perceptible at higher magnifications. However, for moderate to medium magnification applications where one needs correct images (such as to read numbers, etc.) then the optional prism should be suitable. For film photography, the telescope (with our optional camera adapters) becomes a super sharp 540 f5.4 ultra telephoto lens, showing about 4.5 degrees across the diagonal of a 35mm camera film plane. And for CCD imaging operations the telescope at prime focus can show about 0.86 degree across the diagonal of a common 2/3" detector (such as that employed on some of our SBIG CCD systems. Optional techniques and hardware permit imaging of galaxies, nebulae, the planets, or of wildlife. The NP101 can operate on any of a number of suitable optional German Equatorial or for extreme ease of use or portability consider our alt-azimuth mounts including:
Furthermore, this is a telescope one can grow with since most of the accessories that one would buy for this telescope are upwardly compatible with any larger telescope that one is likely to buy at Company Seven.
MECHANICAL CONSTRUCTIONTeleVue NP101's claim to fame beyond the already very good optical properties of its predecessors is that the NP101 is so compact that it can be carried onto a commercial airplane. There are few other first rate telescopes of this aperture. Fewer still are so compact that they can be carried onto a commercial aircraft; but some of these require the user disassemble the telescope into components. It has been our preference that customers not be made to disassemble telescopes in order to make a telescope as portable as the TeleVue NP101, or the Astro-Physics "Traveler" telescopes are. And so the TeleVue NP101 brings the number to two four inch Apos that can make this claim which Company Seven offers. The NP101 has a fully machined aluminum front cell to house the objective lens, and focuser housing is similarly constructed. The objective lens is permanently aligned to the barrel as is the focuser assembly. Unless subjected to gross abuse this telescope will provide many lifetimes of service with no need for any other than cleaning of the front surface of the objective lens using common camera lens cleaning techniques. Its construction is extremely rugged to allow it to withstand all the handling that is typical of airline travel. However, some caution should be practiced not to damage the focuser pinion of any telescope; our experience with this focuser is that with routine handling this will not happen and in its hard shell case is routinely transportable. We find most competing 4" Apo telescopes to be bulkier and heavier than we would like regardless of how good the optics may be. For an example of this consider the now discontinued Carl Zeiss 105 APQ, it is a wonderful telescope modeled after the Astro-Physcis 105 "Traveler", but the APQ was made relatively wide, pig heavy, and bulky with no easy provision for removing and compactly storing its' lens shade. The NP101 does incorporate a retracting Dew Shield/Lens Shade. Our experience is that most customers appreciate the convenience of a retracting lens shade, or one that can be removed then turned around and slid back over the tube into a stored position. Also provided is a thread-on Lens Cover of machined aluminum, in a tube assembly that has an overall length of only 26 inches without diagonal, or 29 inches with it's furnished 2 inch diagonal attached. This is four inches shorter than its predecessor.
Right: TeleVue NP101 telescope focuser (2004 and prior models) without accessories, showing no mar clamp lock mechanism (75,974 bytes).
New Focuser for 2005: in 2005 TeleVue changed the mechanical design of their focuser, the goal of this change is to improve the rigidity and payload capacity of the focuser. This focuser is particularly beneficial to those who entertain CCD or film imaging with the heavier cameras; this design was tested so far with loads including an SBIG STL series CCD camera which approach 5 lbs. (2.3 kg). The former chromed drawtube arrangement consisted of a machined aluminum collar bolted onto the chromed drawtube barrel by three short screws. Tension on the drawtube was applied by one set screw applying pressure onto an internal pad at 12 O'clock. In the 2005 model the drawtube is a one piece arrangement incorporating the non-marring collar clamp mechanism. There is also a clamp ring within the focuser body surrounding the drawtube, this provides uniform and more secure tension with less image shift when locking it down. The end ring is incorporated into the machined drawtube so there is no longer any way the payload can tilt at the end of the drawtube. We measured the focus travel distance of the 2005 model focuser drawtube as 1.93 inches (49 mm).
Left: TeleVue NP101 Apo Telescope 2" Focuser (2005 model) with drawtube fully extended. Shown with provided TeleVue 2" right angle Everbrite mirror diagonal (46,940 bytes).
The new 2 inch focuser is of a bead blasted aluminum construction, entirely black anodized. Aesthetically the difference between the 2005 and prior focuser models is a matter of taste, but there is a practical improvement in performance. This focuser will be gradually phased in on all TeleVue telescopes provided with the 2 inch focuser.
The mounting collar provided for the optical tube assembly is a two piece bracket, machined of aluminum stock and black anodized. On one side of the collar is an Allen head screw, while on the other side is a manual tension adjustment knob so that the use of a wrench is not necessary. This design permits one to adjust the grip on the barrel so that the telescope may be easily moved back and forth to compensate for changes of accessory loads that may affect the balance of the telescope on a mount. However, telescopes with the length and weight of the NP101 require that this collar be snugged tight to reduce or eliminate undue wavering of the telescope in the collar. For those using the telescope for applications including astrophotography or CCD imaging which demand extremely rigid support of the telescope, Company Seven can provide either a second TeleVue clamp. Or Company Seven can provide conventional mounting rings (sold by the pair) with platforms which will accommodate options including photo guide telescopes. The fabric lined mounting collar has three 1/4"-20 tpi threaded sockets in the base to facilitate mounting the telescope onto a variety of tripods and mounts. At the 10:30 and 1:30 o'clock positions on the top of the collar there is a dovetail platform to accommodate a variety of TeleVue options including the "Starbeam" sight, or a
The telescope is furnished with a TeleVue 90 degree 2 inch diameter "Everbrite" precision mirror diagonal (1/10th wave P-V quoted). This diagonal has a durable reflective coating described above. The male 2 inch barrel is threaded to accept 48mm photo and visual filters. The interior is fully anti reflection ribbed and coated.
Left: TeleVue Everbrite 2" Mirror Diagonal and TeleVue 2" to 1.25" Reducer showing no mar clamp lock mechanisms (64,909 bytes).
The objective (front) lens cell, dew shield, lens cover, focuser housing, 2 inch mounting collar, and diagonal are anodized in a lustrous glass beaded black satin. The barrel is powder coated in a textured neutral Ivory; the powder coat feels like a textured smooth plastic covering which is quite comfortable to manage even in extreme cold or damp climates. The interior of the optical tube assembly is lined with an anti-reflective covering unique to TeleVue telescopes, which is then finished with anti reflective black paint.
Also included with the telescope is a die cut, foam lined hard shell carrying case with latch closures. This case dimensions are 38-1/2 x 10-1/2 x 9-1/2 inches. And it has extra space to accommodate several 1.25 or 2 inch oculars (up to the massive TeleVue 31mm Nagler Type 5 eyepiece - nicknamed by the amateur community the "TermiNagler"), camera adapter, etc. And in a nice touch the case has a cutout provision for the "Starbeam" or Rigel QwickFinder sights. The case will fit into the overhead storage area of most commercial aircraft (one exception being the L-1011). However, many airlines do not permit such an "oversize" package on board. Even if they do you will not be too popular with other passengers so you might ask a Flight Attendant to store the telescope for you - possibly in the garment bag storage area. By the Fall of 2001 we anticipate offering an optional padded soft case that will facilitate getting the NP101 telescope safely on all commercial aircraft.
The telescope, in its standard hard shell case is well padded and then packaged for delivery within one box, and then this is placed into another box. You should consider the practicality of simply shipping telescopes (and mounts) such as this ahead by a priority air service (FedEx, UPS, U.S. Mail, etc.) if you are concerned about cutting down the number of bags you can carry on or check in. Furthermore, shipping the telescope could reduce risks of loss or damage in shipment, and inconvenience and risks of managing bags through airport terminals. Company Seven does offer wonderfully engineered Airline Transport Association transport and shipping cases for telescopes, mounts, and accessories.
This is a convenient astronomy guide book written for those who may be newer to the hobby, or who appreciate a more fun approach to reading. This book is an interesting read for those who appreciate the historical insights to the life of Charles Messier (b. 26 June 1730 in Lorraine France, d. 12 April 1817 in Paris), the French astronomer who gave us the Messier Objects catalog of celestial wonders. The author performed extensive research in the USA and overseas to accumulate the knowledge that he conveys in a very readable format. A delightfully illustrated handy book with some beautiful color pictures, color illustrations and charts, and with black and white photo plates of the Messier Objects. The book features photos with visual descriptions by the author with a TeleVue 101 4 Inch f/5.4 and TeleVue 102 4 inch f/8.6 apochromat refracting telescopes.
Company Seven recommends this to those who wish to read an introduction to using amateur telescopes and learn how to use them to star hop or navigate into these first hundred or so deep sky objects. It is well illustrated, good and entertaining reading, and suitable for most children at Junior High/Middle School levels up to adults.
Please refer to our TeleVue News article of 15 September 2005 for more information about this free Ken Graun book promotion.
The mount head is made of fully machined of aluminum which is black anodized, with brass elevation bearings and azimuth nylon bearing providing smooth vertical travel from 10 degrees below the horizon up to 85 degrees overhead, and smooth full 360 degree rotation. Clutches on the elevation axis permits the operate to compensate for changing accessory loads, or with the Azimuth control to lock the telescope in place. The tripod is made of American ash, in a two section extension design providing a range of 3 feet up to 5 feet, with accessory tray/leg brace. The "Gibraltar" mount solved a problem of ease of use for those who are frustrated by the weight and relative complexity of equatorial mounts, and it provides a mount far better suited to terrestrial applications than an equatorial mount or common camera tripod would be. These mounts remain available with either a beautiful ash tripod in natural finish (Yes, ash is the hard wood used to make baseball bats) with black trim, or a in walnut finish. Since it's introduction the "Gibraltar" head has been engineered to accept optional encoders to feed a "Digital Setting Circle" CPU such as that offered by TeleVue and third party units; this helps one to navigate the sky and find objects that might be hard to find particularly from suburban settings.
Company Seven will offer TeleVue and Company Seven padded soft cases to facilitate transport of the telescope. These optional cases will permit one to safely navigate airport terminals and carry the telescope on board!
Above: Company Seven ATA Case custom fitted for a
Features include:
Please contact Company Seven for additional information and pricing.
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Gibraltar Mount Head and Ash Tripod: An incredibly rigid and portable 17 lb. (7.7kg), simple to use mount that cradles a telescope at its center of gravity for ideal balance at any viewing position.
