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-n-go or travel
scope, but not at exorbitant UK new prices – buy used or maybe on your
Stateside holiday!
