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NP127 - f5.2 Nagler-Petzval Apochromat Refractor (5.0 inch aperture)The first, first rate TeleVue 5 inch Apo!
Introduced to the world as the NP127 by Al Nagler at Company Seven in January 2003, the NP127 was in 2006 replaced by this even more capable NP127is.
Responding to the growing aspirations of those pursing astrophotography and CCD imaging, the NP127 is replaced by the 'NP127is' Imaging System telescope. FIRST GLIMPSE
Martin Cohen, Company Seven
Left: Beaming with the pride of a new father, Al Nagler finally reveals his new telescope to the public at Company Seven's showroom 30 January 2003 (111,487 bytes).
The TeleVue NP127 telescope is an f5.2 flat field, four element apochromatic refractor. It can be simplistically looked at as being an upscaled NP101 - TeleVue's highly regarded 4 inch Apo telescope. The NP127 telescope is engineered primarily for the astronomer who seeks very high performance and a versatility that can be provided only by fast apochromatic refractors as this. The NP127's advantages include ease of use and rugged portability similar to fast 4 inch Apos, with the proportionate increase in light gathering power and resolution over those smaller Apo telescopes. Fast Apos such as this are the most versatile of telescopes and they are also the most costly and difficult to produce well. Since the NP127 can provide visual fields of view as wide as 4 degrees at only 12X magnification, its practical uses include panoramic terrestrial applications. At the low to middle magnifications its 1.6X fold increase in light gathering power over the 4 inch Apos provides views and photographs of star clusters, galaxies and nebulae which are striking. While the telescope is also at home in the role of a high magnification, high resolution instrument for observing subtle details on the planets, moon, or double stars.
The NP127 telescope fits neatly into the same 38-1/2 x 10-1/2 x 9-1/2 inch hard-shell carrying case as that provided with the TeleVue NP101 and 102 four inch Apos. In a departure from the conventional TeleVue case arrangements, the 2 inch Everbrite Mirror Diagonal is removed from the telescope and stored in a compartment within the lid of the carrying case; this space can accommodate several other accessories including eyepieces and or camera adapters. The air spaced objective of the NP127 is installed more near the forward edge of the Front Cell to assure a good fit of the OTA in the TeleVue carrying case. We performed visual resolution tests of the NP127 telescope using a variety of eyepieces including the new TeleVue 2.5mm Nagler Type 6 (with and without a Barlow lens!), all results were consistently in line with our good experiences with the smaller proven NP101.
TeleVue developed a new, larger version of the popular "Gibraltar" Alt-Azimuth mount (illustrated below) which is intended for use with the NP127 telescope. The new head is engineered to fit onto the ash tripod as is now provided by TeleVue on the "Gibraltar" mount, but the machined aluminum trunion and carriage arrangement has been enlarged to better accommodate the NP127 telescope. The ash wood tripod is functional and attractive.
Company Seven hopes to eventually display a NP127 telescope as another addition to our "Martin C. Cohen Memorial Telescope Museum Collection"!
While it was first announced to the world at Company Seven on 30 January 2003, we began making the first deliveries of this new telescope just in time for the Mars Opposition of August 2003.
DEVELOPMENT
Compared to other popular telescope designs (reflecting and catadioptric) the well made Apo refracting telescopes offer most natural, high contrast, and three dimensional views of the brighter objects. They also offer the greatest span of visible actual fields of view from low to extreme high magnifications. The shorter Apo telescope tube generally weighs less, impart less torque, and be managed on lighter weight and more compact mounts than achromatic telescopes.
Viewing through a fast Apo is an experience where you are more often able to view the entire painting.
The fast and versatile flat field 4 and 5 inch aperture telescopes pioneered by TeleVue were the first to prove the value of using a refractor for deep sky observing and for imaging. Up to the early 1980's most refracting telescopes were relatively high magnification achromatic instruments typically of f12 or f15 with .965 or 1.25 inch diameter eyepieces which afforded relatively narrow fields of view. These telescopes were physically quite lengthy, and required taller and massive mounts to deal with their torque. By the 1980's optical glass and fluorite crystal lens design innovations made it possible to manufacture comparatively fast apochromatic telescopes of about f9. These faster designs combined with a capability to accept 2 inch diameter oculars permitted the wider fields of view (as much as 2.9x the area of 1.25 inch eyepieces) better suited to deep sky observing. Imagine being able to visit Paris to see the "Mona Lisa", and upon entering the gallery you are fitted with an eye patch on one eye and a soda straw attached over the other - you would be able to see any small area of the painting and as closely as you wish, but you would never be able to see the entire painting - that is life with most other telescope designs! Viewing through a fast Apo provides an experience where you are more often able to view the entire painting.
When comparing a 4 or 5 inch Apo to a mirror or catadioptric telescope in terms of detail and field of view, one could not build a large enough mirror telescope to rival the refractor without having so large an aperture that the field of view observed through the mirror systems would be comparatively narrow - this is where the Apos are unrivaled. And to attain the upper limits of magnification for studies of the planets, double stars, etc., one can simply employ any of the new TeleVue high performance short focal length eyepieces. Or with a negative lens in the form of a TeleVue Powermate (available in 2, 2.5 or 4X), the NP127 becomes a compact high resolution platform outperforming much larger instruments - which most of us do not wish to carry out too often!
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 and now the NP127 reflect 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 4 inch "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 ultra compact NP101 arrived.
While some of us recall the limited production TeleVue 140 telescope of some years ago, the NP127 is closer to an evolution of the NP101 which 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 pass the light through to a second doublet lens at the rear of the telescope. The doublet lens group functions to reduce the effective focal length and to reduce or eliminate curvature of field.
Compact and rugged, versatile and high resolution - the reasons why well made fast Apos are the choice of demanding visual astronomers.
In prior TeleVue telescopes one could in theory remove the rear doublet lens and use the telescope with the objective lens alone in place. But the NP101 and NP127 are a departure from traditional TeleVue Petzval derivatives. Incorporating TeleVue's best air-spaced special dispersion doublet lens with what appears to be a simple doublet telecompressor/field flattener, the NP127 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 12X and a tack sharp field of view of as wide as 4 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, CCD or video imaging, and film photography as well as visual and astrometric astronomy.
The TeleVue NP101 and the NP127 telescopes 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 Apos ever made. They occupy a unique niche in the telescope inventory since no other telescopes exactly duplicate their out of the box versatility and ease of use. These telescopes provide false color-free, sharp, clear and high contrast images. And since the best apochromatic refractors are among the most difficult and costly in raw materials to make consistently well, these 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.
Left: TeleVue NP127 Front Cell w/Lens Cover. Note the unprecedented transparent lens cover, this makes it lighter weight than a fully machined cover - and adds some "way cool" factor (68,652 bytes).
The system's 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 NP127 telescope are engineered to match the characteristics of each glass type and curve radii. This process improves color rendition, 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 about 300 times the light gathering power of the unaided human eye - about the same as typical 5 inch doublet systems. On most nights, the settling down time for the optics will be the order of minutes; from room temperature to freezing it rarely will require more than 45 minutes to an hour for the optical tube assembly 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 at times eclipsing one another! 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 mm "Nagler" or 6mm "Radian") take a walk on a apparently three dimensional Moon, resolving objects as small as 3.5 km in diameter. Or follow the lunar terminator throughout the phases; optional neutral density filters are offered by Company Seven to attenuate brightness and make observing more comfortable.
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 surrounding the Sun, and the sheer curtain-like Prominences as they erupt from the Sun out into the blackness of space!
Right: TeleVue NP127 Telescope 2" Focuser for models up to mid 2005 (72,315 bytes).
Studied under a higher magnification M13 (the "Messier" catalog 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 multi purpose 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". Read that book and then consider the 60 per cent improvement in light gathering power that the aperture advantage alone of the NP127 should provide!
The NP127 compares favorably against many telescopes in field of view, but in fairness the cost of the NP127 like most other serious Apo's (equipped with either an optional Alt-Az or Equatorial mount) is positioned at a higher cost than most amateur telescopes. And as a practical matter for some applications in astronomy the nominal match of the NP127 exit pupil to an average dark adapted human eye will be obtained at magnifications of between 18X and 25X. The best performance and viewing comfort will be obtained at all magnifications if a wise choice of good quality oculars is made however since the NP127 telescope incorporates a field flattening element then it is technically compatible with several of the simpler eyepiece designs. Most of our NP127 customer employ an optional good quality Barlow lens or a TeleVue "Powermate" amplifying (negative) lens, or optional wide angle "Nagler" or 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.
For film photography, the telescope (with our optional camera adapters) becomes a super sharp 660 mm f5.2 ultra telephoto lens, showing about 3.7 degrees across the diagonal of a 35mm camera film plane. And for CCD imaging operations the telescope at prime focus can show an area about 0.7 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 NP127 can operate on any of a number of suitable optional German Equatorial mounts including:
This is a telescope one may not outgrow, but 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 one will not feel trapped by the cost of accessories for the second telescope. It has been argued by many experienced observers that while no one telescope can do it all, the Apo refractor is most versatile. And it can be complemented by a large 18 to 22 inch aperture Dobsonian telescope such as those we offer by AstroSystems.
The NP127 has a fully machined aluminum front cell to house the objective lens. Changes since mid 2005 include the new 2" focuser where the cell with its housing and drawtube are 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. The NP127 does incorporate a retracting Dew Shield/Lens Shade.
Also provided is a thread-on Lens Cover of machined aluminum outer frame with a transparent acrylic window. A hand knob is provided at the center of the window with a rubber grip grip ring. This design notably reduces the weight of the otherwise heavier machined aluminum cover. And it is another innovation so far unique to the NP127!
The precision TeleVue 2 inch focuser is a rack and pinion design with a tension/lock screw which helps to lock focus for uses including photography; this is one of the smoothest focusers made. The 1-1/2 inch diameter machined aluminum hand knobs resemble brushed aluminum mag wheels available for radio control model cars. The knob hand grips are rubber covered to facilitate operation in all extremes; even when wearing gloves all the controls on the telescope are easy to manipulate. The set screw has an easy to grip knurled head, this permits one to adjust resistance of the focuser to its draw tube thereby compensating for heavy loads that might otherwise cause an unintended shift of focus.
New Focuser for 2005: in 2005 TeleVue changed the mechanical design of their focuser and this is how all NP127's sold by Company Seven will be delivered. 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 draw tube arrangement consisted of a machined aluminum collar bolted onto the chromed draw tube barrel by three short screws. Tension on the draw tube was applied by one set screw applying pressure onto an internal pad at 12 O'clock. In the 2005 model the draw tube is a one piece arrangement incorporating the non-marring collar clamp mechanism. There is also a clamp ring within the focuser body surrounding the draw tube, this provides uniform and more secure tension with less image shift when locking it down. The end ring is incorporated into the machined draw tube so there is no longer any way the payload can tilt at the end of the draw tube. We measured the focus travel distance of this focuser draw tube as 2 inches (52 mm).
Left: TeleVue NP127 telescope focuser (introduced in mid 2005) with draw tube fully retracted, showing the 2" diameter no mar clamp lock mechanism (51,070 bytes bytes).
The new 2 inch focuser is of a bead blasted aluminum construction, entirely black anodized in a lustrous finish. 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.
A machined aluminum bar is bolted on spanning the two mounting rings across the top to add extra rigidity, this does not seem to be necessary but no astronomer ever complained about too rigid a support system. 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
Right: TeleVue NP127 telescope mounting rings and stiffening bar (58,808 bytes bytes).
A machined aluminum mounting plate is provided installed at the 6 o'clock position on the mounting rings. The rectangular plate is provided with two 1/4 inch 20 tpi stainless steel studs installed with wing nuts which makes the NP127 ready to slip onto the TeleVue alt azimuth mounts. The mounting plate features several other tapped and threaded holes to facilitate installation of the NP127 onto other mounts or plates.
This ring and bar set is a good arrangement for those using the telescope for applications including visual, or light duty astrophotography or CCD imaging which demand extremely rigid support of the telescope. However, for those of our customers interested in employing heavier piggyback loads atop the NP127 (guide telescopes, large finder, etc.), then Company Seven can provide optional alternative rings and mounting plate hardware.
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 "Everbrite" mirror introduced in 1999 features a high technology dielectric coating developed originally for military optics used in hostile environments such as blowing desert sand. This TeleVue 2 inch diagonal has no aluminum or other reflective metal coating. Instead, the reflective element consists of about fifty layers of thin film oxides similar to those used in antireflection coatings. These coatings are deposited into the glass 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. This coating will provide optimum performance and a lifetime (or more) of use.
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.
A TeleVue 2 inch to 1.25 inch reducer adapter is furnished to permit the use of 1.25 inch diameter accessories. The reducer is engineered with a collar to prevent long barreled eyepieces even with one filter attached from "bottoming out" against the mirror. This diagonal permits an observer to employ any of a broad selection of 2 or 1.25 inch diameter oculars. The lock screw with a knurled head that is at the proximal (to the operator) end of the female 2 inch barrel adjusts tension to retain accessories such as the 2 to 1.25 inch reducer or lenses.
The telescope objective (front) lens cell, retracting dew shield, lens cover metal frame, focuser housing, 2 inch mounting collar, and diagonal are anodized in a lustrous glass beaded black satin; the preproduction model we first evaluated was gloss black anodized. The barrel is powder coated in a textured neutral Ivory; the powder coat feels like a thick 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 antireflective 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 very lightweight formed ABS case has and compartment in the lid with a hinged door revealing extra space to accommodate the 2" Everbrite diagonal, and several 1.25 or 2 inch oculars (up to the massive TeleVue 31mm Nagler Type 5 eyepiece - nicknamed by the amateur community the "TermiNagler"), or camera adapter. The case will fit technically 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 fellow passengers when you take up an entire overhead space, and so you might ask a Flight Attendant to store the telescope for you - possibly in the garment bag storage area.
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. If you wish to travel with your NP127 then ask Company Seven about out 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.
In addition to our own ATA cases, Company Seven will offer optional padded soft cases to our customers in order to facilitate transport of the telescope.
* The telescope is capable of operating at magnifications greater than listed in this briefing above.
Above: Company Seven ATA Case custom fitted for a TeleVue NP101 telescope and accessories (138,840 bytes).
Features include:
Please contact Company Seven for additional information and pricing.
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