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101 mm f5.4 Apochromat Refractor (4.0" aperture)
Discontinued April 2001, replaced in August 2001 with new NP101 telescope.
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. Recent optics innovations had resulted in relatively fast telescopes of f9 or so, compared to the previous common f12 to f15 ratio Achromat this afforded wider fields of view better suited to deep sky observing. Since the best apochromatic refractors such as the 101 are the most difficult and costly in raw materials to make well consistently, these 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 "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 101 is a notable improvement we can only imagine how such a 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. The "101" and "Renaissance" telescopes are a fifth generation TeleVue four element refractor design succeeding the original 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. Al Naglers patented four element design is based on the "Petzval" concept where a two element air spaced objective lens 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 functions to 1) reduce the effective focal length, and 2) reduce or eliminate curvature of field.
Incorporating TeleVue's best 101mm aperture air-spaced "SD" special dispersion doublet lens with a fluorite doublet telecompressor/field flattener this provides flat field wide angle views. 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! A multi layer coating process of the lenses, and on all the TeleVue eyepieces prevents light reflection off the surface of, or between the lenses; 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 caused by internal reflection. 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 "101" series telescopes introduced in 1998 are the first large TeleVue Apochromatic refractors which Company Seven found to be truly competitive in optical performance with the best 4 inch aperture Apos ever made; providing visually false color-free, sharp, clear and high contrast images. The TeleVue 101 remains the worlds fastest, flat field apochromatic 4 inch telescope - while the brass "Renaissance 101" also remains the world's most beautiful.
PERFORMANCEThe objective lens of the 101 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) common to less sophisticated achromatic refractors, and better than a number of older triplet and modern doublet apochromat designs. A fluorite doublet telecompressor/field flattener lens group provides flat field, wide angle capability. Spherical correction is very good also with the air gap 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 objective's four air to glass surfaces have a multi-layer anti-reflection coatings that improves overall light transmission across the visual wavelengths and from 400nm to well beyond 700nm. Overall the complete system provides about 180 times the light gathering power of the unaided human eye. On most nights, the settling down time for the lens is on the order of minutes: from room temperature to sub-freezing conditions it rarely requires more than 30 minutes to acclimate. The lens is so well figured that the consistency between telescopes is quite good, and each is capable of operating at very high magnification cleanly (with "Barlow" or "Powermate" optional lenses). This telescope reaches that threshold necessary to routinely obtain meaningful views of the planets showing several bands and their shades of color (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 101 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 has since been replaced by the improved 101 and 102 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 7mm Nagler eyepiece (71X, 1.08 AFOV), and a TeleVue Barlow lens to increase the magnification by 1.8X. The 101 compares favorably against many telescopes in field of view:
In fairness, the cost the TeleVue 101 (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 "101" 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 101 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 use able magnifications which are necessary for observing small bright objects including planets, and double stars. The telescope includes the TeleVue 2 inch diameter "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 new TeleVue 2 inch diagonal has no aluminum or other reflective metal coating. Instead, the reflective surface consists of 52 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 ED ultra telephoto lens, showing about 4.54 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 the planets, or of wildlife at much higher magnifications. With optional 2" and 3" long x 2" diameter extension tubes, it is possible to observe at close distances for use as a "long distance microscope". The TeleVue 101 can operate on any of a number of 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 CONSTRUCTIONThe 101mm has a fully machined aluminum front cell to house the objective lens and focuser housing. 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 101 telescope incorporates a retracting Dew Shield/Lens Shade. Also provided is a thread-on Lens Cover of machined aluminum in a tube assembly that has an overall length of only 33 inches with it's 2 inch diagonal attached. 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 model car brushed aluminum mag wheels. 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. The lock screw that is in the draw tube ring at the proximal (to the operator) end of the draw tube adjusts tension to retain accessories such as the 2 inch diagonal, or a camera; this set screw is captive so it will not easily come out.
The mounting collar is a two piece bracket. On one side of the collar is an Allen head screw (wrench provided - but not necessary), while on the other side is a tension adjustment knob. 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 101 require that this collar be snugged tight to reduce or eliminate undue wavering of the telescope in the collar. For those interested in applications such as astrophotography or CCD imaging, Company Seven can provide optional conventional mounting rings (by the pair) which will also 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. A 2 inch to 1.25 inch reducer adapter is furnished to permit the use of 1.25 inch diameter accessories. 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; this set screw is captive and so it too will not easily come out.
The objective (front) lens cell, focuser housing, mounting collar, and diagonal are anodized in a lustrous black satin. The barrel is powder coated in the customers choice of either a mottled Forest Green, or textured neutral Ivory (as illustrated above). 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 is 38-1/2 x 10-1/2 x 9-1/2 inches in dimension, and it has extra space to accommodate several 1.25 or 2 inch oculars, camera adapter, etc. And in a nice touch the case has a cutout provision for the "Starbeam" or "Qwick-Point" 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 "oversize" packages 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.
The telescope, in itsw case is well padded and then packaged for delivery within one box, and then this is placed into another box. We suggest that telescopes such as this be sent by a priority air service (Fedex,ÊUPS, U.S. Mail, etc.) to reduce risks of loss or damage in shipment.
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 with black trim, or a walnut finish with solid brass journal and plated brass trim. (Yes, ash is the hard wood used to make baseball bats). 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.
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Right: TeleVue Ash Gibraltar Mount with optional 101 telescope, Starbeam sight, oculars and SkyTour CPU on accessory tray.
