C-7 Home Page C-7 News Products and Services Product Lines Order Consignment Library

TeleVue Distribution History TeleVue Index News Notes & Interesting Articles Pricing Products

Accessories Eyepieces/Oculars Mounts Starbeam Sight Telescopes

TeleVue 76 SD Doublet Apochromat Refractor (3.0" aperture)

"among the most perfectly made, compact and highly versatile refracting telescopes"

Above: TeleVue 76mm telescope optical tube assembly in Ivory finish shown with lens shade retracted. Focuser is model as provided on late 2005 and later models, shown with drawtube retracted.

History: In the Fall of 1986 TeleVue announced a new telescope, the 76mm "Oracle". The 560mm f7.4 Oracle would set a new standard of versatile excellence for very compact refracting telescopes. Prior to this there had been short focal ratio telescopes on the market, but few rivaled the Oracle particularly when operating at the high magnifications necessary to study the planets. The Oracle was a 76mm Apochromatic telescope made in a triplet design (three lenses matched to work as one) with TeleVue's 2 inch focuser; this combined with wide angle eyepieces provided the light gathering capacity coupled with extraordinary wide field of view ability (showing up to 4.9 degrees!) to reveal the entire Messier Catalog of deep sky wonders or be employed for panoramic viewing of a seashore or countryside. And the Oracle also had the high power clarity to see the major changing features on the planets, and still it was carry on luggage portable! The Oracle became a choice first telescope for astronomers, and a good compact second telescope for those who owned instruments too inconvenient to set up routinely. The "Oracle" would also introduce the TeleVue name to the birding community. However, the difficulties of producing high performance triplet apos, and rising costs resulted in the discontinuation of the "Oracle".

In March 1993 TeleVue introduced the 70mm "Pronto", an ED doublet refractor telescope. While highly successful for birding and accepted by the astronomy community as a whole, Company Seven believed that a need was not being met for a telescope of improved performance for astronomy. The Pronto has the field of view and versatility for many uses however, it's design limits it to about 150X and so we judged this to be just below the threshold necessary to routinely obtain meaningful views of the planets. Martin Cohen of Company Seven and others regularly asked Al Nagler at TeleVue to develop the idea of an about 80mm f7 well corrected Apochromatic telescope, with a 2 inch focuser and degree of correction that would result in performance suitable for observing the "Messier Catalog", and the planets, while also retaining good portability. Well, Al Nagler listened and in June 1998 he responded by introducing the "85" telescope!

In the Summer of 2001 TeleVue announced the "TeleVue 76" telescope. At first we at Company Seven (geared mostly for astronomers - but tolerating birders and nature watchers) were somewhat mystified since we are very happy with the TeleVue 85. The 85 telescope has become so well regarded in many applications, and so many customers are buying the 85 as a first telescope, or as a versatile traveling second telescope.

Left: TeleVue 76mm telescope with lens shade extended, with optional TeleVue Panoramic Mount Head with Handle and TeleVue 22 mm Nagler Type 4 eyepiece. Focuser shown as provided on late 2005 and prior models (93,422 bytes).
Click on image to see enlarged view (141,672 bytes).

But as Al Nagler has done before, he looked into his Crystal Bowl (probably made of some exotic glass) and has again seen the future - he predicted there was a market for a highly perfected compact telescope, superior to the well regarded Pronto and many other spotting telescopes, more compact than the reference standard TeleVue 85, and more versatile than the best traditional spotting telescopes. The TeleVue 76 has also become popular as a high quality wide field capable visual and imaging "Super Finder" for installation onto larger astronomical telescopes.

PERFORMANCE

The 76 is among the most perfectly made, ultra compact, and highly versatile refracting telescopes. While at first glance the compact 480mm focal length TeleVue 76 apochromat appears nearly identical in appearance to it's cousin the achromatic 480mm "Pronto", the 76 a more sophisticated optical design affording improved color correction and a 15% increase in light gathering power with notably higher useful magnification. It is closer to being thought of as a scaled down TeleVue 85.

The objective lens of the 76 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. This design allows very good color correction - comparable to the TeleVue 85, and markedly superior to the traditional achromatic and older triplet apochromat designs. The chromatic performance is the best that is possible in a doublet design with the best glass obtainable today. The spherical correction is very good also, with the air gap contributing to this correction. Images of the birds and wildlife, and of stars and the planets are presented in their natural colors. Daytime targets viewed at commonly used magnifications will appear quite three dimensional and sharp and high contrast without annoying purple fringes (secondary color) common to less sophisticated refractors. The efficiency of light throughput is very high, and so this telescope is likely to present images that appear brighter than those provided by many of the larger aperture traditional spotting telescopes.

The objective's four air to glass surfaces have a multilayer antireflection coatings that improves overall light transmission to greater than 94% in the visual wavelengths. So, the system has about 113 times the light gathering power of the unaided human eye making it through the objective lens. On most nights, the settling down time for the lens is on the order of minutes, and even in subfreezing conditions it rarely requires more than 20 minutes to acclimate from typical room temperature.

The lens is so well figured that it is capable of operating at 200X or more cleanly with optional lenses; this 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, the Cassini division on Saturn, the polar cap on a fiery red Mars. With an eyepiece that shows 1/2 degree field or so, take a walk on our apparently three dimensional Moon! or follow its terminator throughout the moons phases (optional neutral density filter suggested to tone down its brightness). It should resolve objects on the moon as small as 5.9 km in diameter; it will see the four largest moons of Jupiter and their shadows cast on the surface when they transit past the planet! On days where the seeing conditions permit it, magnifications much higher than 60X (common to most of the best traditional spotting telescopes) are practical; this makes the 76 a good compact telescope for long distance observing of birds of prey, or distant nesting birds. The versatility is made possible in large measure by the f which is capable of accepting the broadest possible selection of 1.25 or 2 inch eyepieces, Barlow (negative) and some positive lenses, camera adapters, and filters.

Configurations: Since many people who will buy this telescope already own some components that are compatible, and others wish to buy only the optical tube for use as a super "finder" or photo guidescope for a larger telescope, TeleVue makes the 76 available in two basic hardware configurations:

• Optical Tube Only - the 76 telescope with 2 inch focuser (as shown above), with fitted carrying bag.

  and

• Complete Telescope - as above but also with Mounting Collar, 2" Everbrite Diagonal, 2" to 1.25" Reducer.

Each is available with the optical tube finished in either textured Green or in Ivory.

Customers who own no telescope accessories usually should buy the complete telescope package since it is usually not cost effective to buy all other accessories "Ala Carte". Customers who already own a telescope with accessories, and who are willing to share a diagonal and eyepiece may do well to buy the optical tube only with optional mounting hardware.

All "Complete" 76 models include the TeleVue 2 inch diameter "Everbrite" diagonal (or "zenith") mirror. The "Everbrite" mirror 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 antireflection 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 5 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 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 prism should be suitable.

With TeleVue's 2" focuser and a matched wide angle ocular the 76 reveals its extraordinary wide field of view ability showing up to 5.48 degrees at 9X to be employed for panoramic viewing of a seashore or countryside, or to reveal much of the Messier Catalog of deep sky wonders. 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 see the form of large Nebulae such as the Veil and North American Nebulae! With an optional low magnification eyepiece our TeleVue 76 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 "salt and pepper" appearance even from suburban skies on a clear night.

The 76 with its' tack sharp, wide fields of view will be most often be used for birding or nature watching or wide sky astronomy. Typically it will be best to start off with at least one optional eyepiece in the 20 to 30X or so range; this may provide an actual field of view of from 2 to 3.7 degrees. Optional eyepieces for panoramic views may provide as wide as 5.5 degrees, and useful high magnifications of more than 200x comparing favorably against many telescopes:

• 1.9 degrees at 22X for a common 3 inch achromatic refractor,
• 3.8 degrees at 20X for the most sophisticated 3 inch spotting telescopes, which are most commonly limited to magnifications of 60x or so.
• 1.3 degrees at 32X for an 3-1/2" Maksutov-Cassegrain.

In fairness, the cost the 76 (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 "76" exit pupil to an average dark adapted human eye will be obtained at magnifications of between 11X and 15X, while the best performance will be obtained at all magnifications if a wise choice of well corrected oculars is made - this is not attainable with several of the simpler eyepiece designs. An optional good quality "Barlow" amplifying (negative) lens, or long eye relief TeleVue "Radian" ocular (introduced in 1999), or ultra wide angle Nagler eyepiece is suggested to attain the highest useable magnifications.

For film photography, the telescope (with our optional camera adapters) becomes a 384 f5 Apo ultra telephoto lens, showing about 6.4 degrees across the diagonal of a 35mm camera film plane. And for CCD imaging operations the telescope at prime focus can show about one 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 distances of as close as about ten feet for use as a "long distance microscope".

A particular joy of this instrument (and the TeleVue 85) is that even when equipped with an optional suitable mount the set is well within the limits for those who prefer a completely "carry-on luggage" degree of portability. A few larger refractors may be carried on, but then these will require a notably heavier mount that must be packaged and checked in separately. The TeleVue 76 can operate with a much lighter weight camera tripod, ideally with a well designed alt-azimuth head such as the TeleVue "Telepod" as illustrated above; such a head design maintains the telescope well balanced throughout its travel to zenith and this head has adjustable elevation ad azimuth clutches. 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 CONSTRUCTION

The 76 mm has a fully machined aluminum front cell to house the objective lens and focuser housing, and a retracting dew shield/lens shade which is threaded for our optional filters. Also provided is a thread on lens cover of machined aluminum in a tube assembly that has an overall length of only 17-1/2 inches with its 2 inch diagonal attached. The objective lens is permanently aligned to the barrel as is the focuser assembly. Unless subjected to gross abuse this telescope can provide several 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. Company Seven does offer optional highly perfected protective and polarizing filters that can provide protection to the front element of the TeleVue 76. But while dew and typical evening frost will not harm the telescope (optional heaters can prevent these nuisances from prematurely shutting down your evening session) the telescope and conventional eyepieces are not waterproof immersible. Customers who anticipate exposing their telescope to very harsh environments which may include high humidity, mildew, immersion in water or other contaminants, or shock and extreme vibration may wish to consider our 100g shock rated Leica Televid spotting telescopes.

The precision TeleVue 2 inch focuser is of a rack and pinion design with a tension/lock screw; this is one of the smoothest focusers made. The 1-1/2 inch diameter machined aluminum hand knobs resemble model car 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. Its construction is extremely rugged and will allow it to withstand handling that is typical of airline travel. However, some care should be taken to protect the focuser pinion of this or any similar telescope from impact.

Right: TeleVue 2 inch Focuser as provided on the 76 through late 2005 (shown here on a TeleVue 85 telescope) without accessories. Notice the no mar clamp lock mechanism (53,195 bytes).

The focuser lock 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 and so it will not easily come out.

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).

For convenience and safety the 2005 model focuser adds a second clamp knob on the drawtube lock, and another for the 2" accessory clamp. These are provided so that the observer may find at least one lock convenient to reach regardless of where the telescope is pointed. The second screws also adds a measure of safe redundancy and distributes the pressure over two screws around the clamp making it a bit easier to attain a grip on heavier accessories. The lock screws provided on the new focusers which adjust tension to retain accessories such as the 2 inch diagonal and those which apply drag or lock the drawtube can thread compeletely out of their boss; these are not captive as on the prior model.

Left: TeleVue 76 Apo Telescope 2" Focuser (late 2005 model) with drawtube fully extended. Shown with provided TeleVue 2" right angle Everbrite mirror diagonal (65,032 bytes).
Click on image to see enlarged view (174,960 bytes).

The new 2 inch focuser is of 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 is a two piece bracket provided with the complete TeleVue 76 telescopes, optional for TeleVue 76 optical tubes sold alone. 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. For photography, 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 "Piggycam" piggyback photography mount.

As mentioned above the complete telescope is furnished with a TeleVue 90 degree 2 inch diameter "Everbrite" precision mirror diagonal (1/10th wave P-V quoted). The male 2 inch barrel is threaded to accept 48mm photo and visual filters. The interior is fully anti reflection ribbed and coated.

Right: TeleVue Everbrite 2" Mirror Diagonal and TeleVue 2" to 1.25" Reducer showing no mar clamp lock mechanisms (64,909 bytes).

A TeleVue 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 front lens cell, focuser housing, mounting collar, and diagonal are finished in a lustrous black satin anodizing. The barrel is powder coated in the customer's choice of either a mottled "Forest Green" or powder coated in a neutral Ivory finish. The optical tube assembly is finished internally with an efficient antireflective method unique to TeleVue telescopes.

The telescope is furnished with a dense polyester foam lined nylon carrying case with a zippered lid. This case has extra space to accommodate a selection of 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.

TELEVUE 76 mm TELESCOPE SPECIFICATIONS

Every U.S. registered buyer of this new telescope will receive The Next Step - Finding and Viewing Messier's Objects! A copy autographed by the author Ken Graun will be mailed by TeleVue to any U.S. customer who buys and registers any TeleVue telescope after 15 September 2005 at no cost.

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.

SUGGESTIONS

• Panoramic Mount: Cradles the telescope at its center of gravity for ideal balance at any viewing position. Vertical travel from -17 degrees (below horizon) up to +85 degrees, with full 360 degree rotation. Head is precisely machined of black anodized aluminum, with brass bearings and clutches on both axes. American ash wood tripod, two section extension design, with accessory tray/leg brace.
  
  
• Telepod Head: Head provides vertical travel from -17 degrees (below horizon) up to +85 degrees, with full 360 degree rotation. It is precisely machined of black anodized aluminum, with brass bearings and clutches on both axes. Can be attached to most camera tripods.
  
  
• "Starbeam" Finder: beautifully machined and black anodized aluminum, on a quick release machined hardware. Battery powered illuminator is adjustable in brightness; it projects a 10 arc minute diameter red dot onto a transparent 40mm clear aperture window so that the dot appears to be over wherever the scope is pointed. Six arc minute accuracy makes "star hopping" easy.

• Eyepieces: Plossl, Orthoscopic, and traditional Erfle wide angle eyepieces show sharp images only in the center of the field when employed with relatively fast f/ratio telescopes such as this. These eyepieces may be acceptable to you as long as you realize this limitation and if find this unobtrusive. If you object to less than perfect images approaching the edge of the field, then Company Seven recommends the use of TeleVue designed "Nagler", "Radian", or "Panoptic" series eyepieces. These oculars provide tack sharp flat field images and will bring out the most in your "76" (and many other) telescope. A 22 mm to 35mm focal length eyepiece can also make the telescope also serve as your finder. Please refer to the brochure and the test report/data generated by Company Seven enclosed with our telescopes for descriptions of these items and additional accessories.
  
  
• Eyepieces: Company Seven provides excellent technical support and advice and in addition to the factory literature we include printed information with each telescope that will help you to make wise decisions. But basically speaking, the typical observer will want to be equipped with at least three magnifications. These may be accomplished by the proper selection of optional eyepieces, possibly with a magnification increasing lens that may double (or more) the magnification of the telescopes.
  
  
  • most people want to see changing features on the planets Jupiter, Mars, Saturn, and Venus. For these objects, it will be best to equip the telescope to operate at about 200X or so. The simple alt azimuth mounts such as the Telepod limit the observing to about 200X, so to exceed this we suggest the use of tracking, equatorial mounts.

  • For Deep Sky (and nature/terrestrial) observing, or for use as a finder telescope we suggest you equip the telescope with relatively low magnification wide field of view ocular.

  • Many people enjoy having an eyepiece that provides about 1/2 degree or so field of view since this can provide good close up views of the full Moon, the Sun (with optional solar filter), many deep sky objects, and terrestrial objects (on steadier days).

  Eyepiece designs such as the Plossl, Orthoscopic, traditional Erfle and wide angle eyepieces show sharp images only in the center of the field when employed with telescopes as fast as this. These are acceptable as long as you realize this limitation, and find this unobtrusive. If you object to less than perfect images at the edge of the field, then Company Seven recommends the TeleVue "Nagler", "Radian", or "Panoptic" eyepieces. Oculars such as these provide superb flat field images and will bring out the most in your 76 and many other telescopes.
  

• Equalizer: A slip fit machined bronze, heavy 2 to 1.25 inch diameter reducer adapter. Helps to keep telescope balance when switching to and from light and heavy accessories and eyepieces. Particularly helpful when using telescope with Alt-Azimuth mounts.

• Barlow Lens: Company Seven suggests you consider any of a number of 1.25 inch or 2 inch diameter Barlow lenses that we offer to double or more than triple your magnification. Contact us for suggestions on how to to best meet your goals.
  
  
• Field Flattener/0.8X Telecompressor: slides into the 2 inch barrel of the TeleVue 76 telescope focuser. This makes the telescope perform as a 384mm f5 Flat Field telescope, with only very slight vignetting at the extreme corners of the film negative. Requires only an optional "T-Adapter" ring for Nikon, Minolta, etc.
  
  
• TeleVue 1.25 Inch Prism Diagonal: 45 degree 1.25 inch diameter precision image erecting prism diagonal with high transmission coating. This is a good choice for those who must have an image erect and correct left to right view, and who do not intend to use the telescope at higher magnifications.

SOME TELEVUE EYEPIECE SPECIFICATIONS WITH THE 76: