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Tele Vue TV-76 Review

Pre-2005 Tele Vue TV-76 on Panoramic mount.

Tele Vue more or less started the small refractor revolution with telescopes like the Oracle and later the Pronto, small scopes that were rugged and easy to mount; scopes that were light and cooled quickly, that you could get viewing with at a moment’s notice and travel with too. Famous reviewer Ed’ Ting got started with a Pronto; me too.

Despite looking like its predecessors, the TV-76 was different, though: the first small Tele Vue you could really call an apochromat, with its ED doublet objective. When it was introduced, apochromatic refractors were rare and expensive. Now that they are cheap and everywhere, is the TV-76 still worth its high asking price?

 

At A Glance

Telescope

Tele Vue TV-76

Aperture

76mm

Focal Length

480mm

Focal Ratio

F6.3

Length

14.5” (363mm)

Weight

~2.7Kg

 Data from Tele Vue.

 

Design and Build

When Tele Vue replaced the Pronto with the TV-76, nothing changed; from the outside at least. In terms of the lens, though, the TV-76 is a proper apochromat whilst the Pronto was really an achromat, despite using a cheap ED glass (mainly, I’ve heard, for marketing purposes).

Optics

Like all Tele Vue refractors, the objective is permanently collimated in a simple cell which keeps helps keep the tube slim. The cell is held on by three dome-head fasteners and factory collimation is achieved by nudging the cell into perfect alignment. It’s a simple system that’s used on all TVs, but it works.

The lens coatings, as you would expect, are top quality.

The Tele Vue TV-76, has a 76mm (!), F6.3 doublet objective lens, with the crown positive element made of a high-quality ED glass (probably FPL53). This justifies it being called an apochromat, but as with other fast ED doublets we have to be a bit careful. Not all apochromats are equal.

An apochromat is a lens that reduces false colour fringing (chromatic aberration) to a minimum, but it’s also one that reduces the effects of spherochromatism – the tendency for an objective to vary its spherical aberration (so effectively optical quality) with wavelength (i.e. colour).

With a fast doublet like the TV-76, designers have to choose which wavelengths to correct – like life, you can’t have it all. And often those designers prioritise blue so O-A stars don’t bloat on images. So fast doublets are often poorly corrected at longer (red) wavelengths. The human eye isn’t very sensitive to red light, so in many cases this doesn’t matter. Except on Mars.

Meanwhile, a longer focal length doublet (like the F8 Takahashi FS-78 shown below), especially if it uses fluorite instead of ED glass, isn’t troubled so much by this problem. You can see this effect in these two graphs of Strehl (an indicator of overall aberration level – 1.0 is perfect) against wavelength for two scopes.

Two 3” apochromatic refractors: Tele Vue TV-76 and Takahashi FS-78.

Strehl at different wavelengths for an F6 doublet, like the TV-76

Strehl at different wavelengths for an F8 fluorite doublet, like the FS-78.

Tube

TV-76: Not much longer than a book, but chunky and heavy!

The other way in which Tele Vue go about making their scopes compact (and they are, the TV-76 is much smaller than the FS-78, or just about any other 3” APO – 14.5” long and a bare 3” diameter) is to use a flocking material in the tube to combat stray light, rather than the traditional knife-edge baffles which need a fatter tube. As far as I can see, the material Tele Vue use is essentially matte black painted coarse sand paper, but again … it works!

The TV-76 is certainly compact, but it isn’t really lightweight for its size. Though the basic OTA weighs about 2.7 Kg, once you add the clamshell ring it comes close to the weight of some much larger scopes (the FS-78 is much bigger but similar in weight). The reason is that the TV-76 is extremely solidly and ruggedly built. When you pick it up it feels, as a friend vividly expressed it, “like one solid chunk”.

The general build quality and style of the TV-76 is the same as other Tele Vue refractors of the last 25 years or so. The tube is powder coated in attractive (and durable) pebble powder-coat and the focuser and sliding dew-shield are black anodised (later versions are satin black). The lens cap is another TeleVue standard: heavy, solid metal and screw-on; it looks great but can be fiddly (and screechy) to fit at the end of an observing session.

I reckon the TV-76 is one of the most attractive ‘scopes out there and certainly the heft, palpable build quality and simplicity give it an “heirloom” feel. It may not have the very finest lens, the very best Crayford focuser, or any gold leaf or brightly coloured anodising, but overall quality is as good as it gets and highly functional.

Tele Vue’s signature screechy thread-on lens cap.

Focuser

The focuser on my TV-76 has been out of production for many years. It is the original-style Tele Vue focuser with a chrome draw-tube and glossy anodising. It comes with the classic and much copied Tele Vue ‘Mag Wheels’. A basic rack and pinion unit it might be, but this old-style TV focuser is incredibly smooth and free from play or image shift. It also looks good.

The modern units are more solidly constructed to take heavier cameras and have dual tensioners which create less image shift on lock-up. My experience is that they have a different feel that is not as fluid, but perhaps more solid and less likely to rack out under load. The most recent versions come with a dual-speed Feathertouch pinion unit built in. I should also point out that a conversion to a 2” Feathertouch, that replaces the main focuser body with an adapter, is available and looks attractive (though you would lose the serial number plate).

Tele Vue make an after-market dual speed focuser pinion called the ‘FocusMate’. It works well, but I don’t recommend it: I know of people (no, not me) who have damaged draw-tubes, cross-threaded screws and lost vital shims (creating image shift) trying to fit it.

Mounting

Mounting is via a clamshell which has three ¼-20 threaded holes. The centre one is for a photo tripod (the TV-76 is small enough), whilst the others are for Tele Vue’s own mounts.

If you want to mount the TV-76 via a Vixen or EQ5-type dovetail, then Tele Vue make a dovetail plate which bolts straight on the clamshell and which has the clever feature of replicating the Tele Vue pattern threads on its base so you can easily move from one type of mount to another.

The clamshell is super-slim and intended to stay-on. You can adjust tension via a winged nut, but it doesn’t hinge and you need an Allen key to remove it.

For these tests I mounted the TV-76 on Tele Vue’s Panoramic and TelePod mounts and a Vixen GP.

Mounting ring base with ¼-20 threads.

Tele Vue’s EQ5 (Vixen) dovetail plate that then bolts straight on a TV mount as well.

TV-76 on Panoramic mount.

TV-76 on Tele Pod mount (with Rolly the cat).

Accessories

The TV-76 comes with a carry-on soft case with room for accessories. If you opt for the package you get a 2” dielectric diagonal (of the highest quality) and a 20mm Plossl eyepiece, as well as the clamshell ring.

If you want a red-dot finder, Tele Vue make one of the very best – the StarBeam (see Panoramic mount photo above) that has a flip mirror so you can use it without craning your neck. The StarBeam attaches to a purpose-cut dovetail slot on the clamshell.

Of course, Tele Vue will sell you as many superb eyepieces as you can afford!

If you buy a Tele Vue scope, Naglers (Ethos, Delos etc) are sure to follow.

 

In Use - Daytime

The TV-76 works superbly as a daytime spotting or birding scope, delivering beautifully crisp, bright, wide views with no significant in-focus false colour. It’s quite compact enough too, though sufficiently heavy that you’d need a good solid tripod and head with a large (preferably fixed) plate (most quick-release plates will be too small and not stable enough).

Since Better View Desired said nice things about the TV-85 many years ago, TVs have developed quite a following amongst birders and with reason – it’s hard (if not impossible) to get a scope containing roof or porro prisms to perform to this level and makes them ideal for spotting that last nuance in plumage. Of course, the TV-76 isn’t waterproof and a standard diagonal gives a mirror-reversed image.

 

In Use – The Night Sky

General Observing Notes

That less-than-perfect graph of Strehl against wavelength (see above) rarely makes itself felt on the night sky. Mostly the TV-76 is free from false colour and delivers wonderful, sharp and contrast-filled views of everything. All aberrations are well-controlled, so stars are nice and sharp to the edge with a good eyepiece.

Cool Down

The TV-76 cools very quickly and benignly so you can use it straight from a warm house up to moderate powers. This surprised a friend when we did a test against his Questar (which takes much longer being a Maksutov). Quick cool-down makes the TV-76 great for grab-n-go.

Star Test

My TV-76 has a decent star test with a bit of under-correction. Reports suggest Tele Vue achieve a good solid ‘better than diffraction limited’ quality with their lenses – maybe 1/5th wave PV. Takahashis are, I think, usually a bit better – often up to 1/8th wave PV. Can you notice the difference? Generally I think not, but perhaps for critical high-power planetary use.

The Moon

The TV-76 does deliver excellent views of the Moon. The good correction for false colour means you get true a lunar monochrome - greys and whites and buffs. At similar powers an achromat like the Pronto spoils with a false-colour purple wash. A Nagler 5mm gives just under 100x and makes an ideal Lunar eyepiece for the TV-76 - the whole Moon fits pleasingly into the field whilst revealing a lot of detail. Plug in a 2x or 2.5x Barlow (or even better, Tele Vue Powermate) and your DSLR will give great photos of the Moon as well, at fast exposures so that tracking isn’t required.

When I tested the TV-76 against a Sky-Watcher Equinox 80, they were generally very similar, but I found that the Equinox produced a fringe of diffuse light around the bright lunar limb at high power that the TV-76 avoids. This (subtle) effect was repeated by the larger Equinox I tested – due, I suspect, to a finer level of polish or perhaps better glass in the Tele Vue.

Planets

I have had very fine views of Jupiter with the TV-76, especially when mounted and tracking on a good equatorial mount. I’ll say it again – a stable mount really matters for seeing planetary detail. In good seeing a 3.5mm Nagler at 137x yields much Jovian pleasure: multiple belts, dark festoons and storms, the Great Red Spot (now faded to a pale buff) and shadow transits are all within the TV-76’s grasp.

Saturn looks similarly fine on nights of good seeing, crisp and aberration free at high power: a perfect tiny ringed planet floating in a black void with subtle shading on the planet and ring shadow in stark relief. A fine 3” APO is the smallest size that will reliably show you the Cassini Division in my experience.

Why then have I never been able to get very satisfactory views of Mars with the TV-76 (and believe me I’ve tried when for years it was my main grab-n-go)? The answer goes back to those graphs at the beginning. Fast ED doublets like the TV-76 tend not to be so well corrected at the red-end of the visual spectrum. Consequently, Mars always looks a bit bloated, with a bit of colour fringing and I can never quite seem to get perfect high-power focus. Compared with the Takahashi FS-78 (which is a great small scope for Mars) this is particularly noticeable.

If you love Mars, then an F6 doublet – TV-76 included - may not be your ideal APO; go for an F8 fluorite doublet or a premium triplet instead.

Deep Sky

The TV-76 works particularly well for low power sweeping and open clusters, with a stunningly wide field (up to 5.5 degrees with a 2” eyepiece like a Nagler 31mm or Pentax 40mm), perfect pin-point stars and no false colour. Unlike some fast APOs, field curvature and coma are very well controlled in the TV-76 and never intrusive. Tele Vue’s push-pull Panoramic mount is great for this kind of viewing.

A 3” scope may have a modest aperture, but it’s already enough to be enjoyable on deep sky (in a way that a 60mm is not) and the TV-76 allows good medium-power views of planetary nebulae, but with a wide enough low-power field for really extended targets, such as the Andromeda Galaxy and the North American nebula.

If you want to image with the TV-76 (and its short focal length and lack of false colour are ideal), Tele Vue make a dedicated field flattener, the TRF-2008, which converts it to F5.

 

Summary

The TV-76 is a wonderful, no nonsense, do-anything small refractor that helped to define the genre. But these days there’s a problem. Sure, it’s beautifully made in that artisanal way, but it’s expensive for a small ED doublet – compared to a Chinese equivalent, but also compared to a Japanese-made fluorite Borg. Even Takahashi’s cheaper FC-76 model can be had for less.

Of course, if you buy a cheap Chinese apochromat you simply don’t get the guarantee of high optical quality you get with Tele Vue. Some Chinese lenses are good to excellent, others less so. Even if you get a good one, chances are it has had a lower level of hand finishing and polishing; it definitely won’t have been individually checked like a Tele Vue.  Consequently, it may suffer more flare, may take high powers less well.

But to survive in the scope market and keep charging super-premium prices, I think Tele Vue need to move towards the kind of absolutely premium optical quality of Takahashi (Borg, TEC and AP too). I would be very sad if Tele Vue stopped making their unique and special small refractors.

The TV-76 is highly recommended as a grab-no-go or travel scope, but not at exorbitant UK new prices – buy used or maybe on your Stateside holiday!

Updated by Roger Vine 2018

 

 

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