Tele
Vue NP-127 IS Review
One thing I have in
common with Ed Ting, that paragon of telescope reviewers, is an interest in
playing keyboards. With Ed’ it’s the piano; with me it’s the pipe organ.
A pipe organ is a big
thing. In Bach’s heyday – the early 1700s – the organ was the biggest and most
complex machine ever built and a small one, say 25 stops, is still as big as a
bus today. The computer changed all that. I have a 27 stop Allen, that plays
and sounds just like the real thing, but is the size of Ed’s piano. How? Well,
of course my “pipe organ” is really just a computer with digital samples
instead of pipes.
This got me to
thinking how wonderful it would be if you could get a telescope like that: push
a button and it’s an RFT; another and it’s a big long focus refractor for
planets; another and you’ve got a Ritchey Chretien astrograph; a fourth and you
get a super-fast, flat field imaging refractor. And all in a package the size
of a TV-76. Dream on: this just isn’t possible – blame Scotty’s unbreakable
laws of physics. But if one telescope comes closest to this do-anything ideal
it must be TeleVue’s expensive-but-delectable NP-127.
At
A Glance
|
Telescope |
Tele Vue NP-127
IS |
|
Aperture |
127mm |
|
Focal
Length |
660mm |
|
Focal
Ratio |
F5.2 |
|
Length |
~800mm |
|
Weight |
9 Kg |
Data from Tele Vue.
Design
and Build
Perhaps more than any other brand, Tele
Vue scopes have a consistent design and finish that extends from early examples
like the 1980s Oracle right up to this current range-topping NP-127: cream
pebble-coat tubes, CNC rings and in-house focusers, slim sliding dew-shields
and thread-on caps.
Originally, you could get the NP-127
with a basic TV focuser, but more recently it’s been equipped with a special
‘Imaging System’ (I.S.) focuser intended for larger CCD cameras.
Optics
The NP-127 has a
four-element (quadruplet) optical system, known as a Petzval, a system it
shares with the NP-101.
For full details of the
Petzval design, see the NP-101 review. Here I will just say that a Petzval has
four lens elements, rather than the usual two or three: a long focal length
(about F11 in this case) ED-glass doublet up front and a doublet field
flattener/reducer lens at the back (in the focuser).
The Petzval concept means
the freedom from chromatic aberration of the F11 doublet, but with a much shorter
tube and an effective focal length, along with excellent correction for other
aberrations such as coma and field-curvature. This means the NP-127 has very good correction for CA, but with an F
ratio of just 5.2 – faster than the NP-101’s F5.4 - and a very flat field to
boot.
The Petzval system has
four main advantages over a normal doublet plus a bolt-on reducer/flattener:
1)
You can still use the scope visually
without swapping components in and out. No swapping of expensive glass bits
isn’t just more convenient, it’s less risky too.
2)
Having the reducer built in and
in-front of the focuser means less messing with spacers and extensions to get
perfect placement and focus.
3)
You get the very good freedom of
chromatic aberration of a long focal length doublet with a much shorter tube.
4)
The spaced doublets cool a bit faster
than a triplet would (and by this size, triplets typically take a long time to
cool).
This ‘I.S.’ version of
the NP-127 has a larger reducer doublet (3” vs the original 2”) in order to
prevent vignetting (fade off in brightness) on large CCD chips, which can be an
issue with Petzvals.
Sounds good? Why don’t
we see more Petzvals, then? The answer is that with
more glass surfaces to figure and tight assembly tolerances, they will always
be expensive to make (in manufacturing terms, an NP-127 is a five
inch APO and a three inch APO in one tube).
Like all of Tele Vue’s
scopes, the NP-127 has a fixed objective lens cell: you can’t adjust
collimation. This has the advantage of lighter weight and a narrower tube (the
OTA is only a few mm wider the lens itself). The disadvantage is that if the
scope goes out of collimation, you can’t fix it.
Coatings of all
elements appear excellent.
NP-127 objective fills
the tube.
Petzval flattener/reducer
lens at the front of the focuser.
Tube
The NP-127’s
tube is typical Tele Vue. It has a powder-coated cream finish on the outside
and matte-black flocking paper on the inside that looks a lot like sandpaper;
there are no internal baffles. Both focuser and sliding dew-shield are finished
in satin-black, though later versions appear to have reverted to
gloss-anodising which I prefer.
Tele Vues have always had screw-on caps, but on this version of
the NP-127 they have gone a step further to make the centre part funkily
transparent; what’s more it has a logoed knob in the middle to make it harder
to fumble and drop it. Sadly, in my view, the latest version has returned to a
solid metal cap. As with many
Tele Vues it is close to the glass and you have to be
careful not to mark the lens when removing it.
Both the
focuser and lens cell are attached by screws or rivets that have been domed off
– they are not thread-on as they are with many more expensive telescopes. The NP-127
isn’t especially big (though much bigger than, say, my FLT-123 which approaches
it in aperture), but it is heavy at 9 Kg.
Personally, I
don’t like the styling of this version of the NP-127, with its heavy focuser
and stubby lens cell. More recent versions have a longer dew-shield and look
more balanced.
NP-127 is a
big, heavy scope compared to other Tele Vues, but no
larger than a Takahashi FS-102!
NP-127’s
fancy, transparent dew-cap.
Focuser
In order to support
large cameras, the NP-127 has a big 3-inch rack-and-pinion focuser with a
micro-focuser as standard and twin lock-screws. The visual back has no less
than four set screws to tighten the clamp-ring. The visual back incorporates a tilt-ring,
adjustable with three set-screws, to allow you to fine-tune camera alignment.
There is no rotator, though, unfortunately.
The focuser is
reasonably smooth and accurate and will take heavy loads; it has plenty of
travel too. But I did notice a bit of image shift when racked out. Overall,
it’s not as smooth and fluid as a Feathertouch. It
also lacks sufficient travel for the very longest focal-length eyepieces.
Unlike a Feathertouch, the focuser is not baffled – it is lined with
that black sandpaper again!
Imaging-system with
micro-focuser and tilt-ring.
Focuser is flocked,
not baffled like a Feathertouch.
Mounting
The NP-127 weighs in
at nearly ten kilos, once you add in rings and diagonal and finder, so it needs
a medium mount or larger. Tele Vue
sell a bigger version of the TelePod head to
accommodate the NP-127, with bigger bearings and a wider yoke. The head goes on
a standard Gibraltar mount.
Rings are not included
with the price of the NP-127. The ones Tele Vue sell are beautifully
CNC-machined, but suffer from the usual Tele Vue clamshell drawback that you
need an Allen wrench to secure them. What’s more, they won’t fit in the case,
making tear down and set-up times much longer than they need to be. The rings
attach to a special plate that in turn bolts onto the Gibraltar 5 head (or a
TV’s Vixen dovetail plate).
For
astrophotography, I mounted the NP-127 straight onto the big 18” flat plate on
my AP 1200 mount via a set of custom tube rings from Parallax with the AP hole
pattern. This arrangement held it very securely and orthogonally.
NP-127 in the
dome, mounted directly on 18” fixed plate with Parallax custom rings.
Accessories: Starbeam finder, Tele Vue CNC rings and plate, Gibraltar 5
mount.
NP-127 ships
in a quality hard case.
Accessories
The NP-127
comes with the same quality hard case they used to use for the NP-101 as well.
Various
accessories are available, including the CNC rings and special Gibraltar 5
head, as described. The Starbeam finder fits straight
onto the rings and of course there are TV’s huge range of eyepieces which work
perfectly with the short focal length of the NP-127 (which some 3rd
party Eps, such as Pentax XWs, may not).
Collimation Problem
I bought my NP-127
used from a UK dealer and though it was properly packed, the shipping carton
was damaged on arrival. The first time I used it – a quick look at Orion - I
knew something was wrong. A friend thought it was fine, but for me it lacked
the wow factor that marks the NP-101 and even Genesis. Star fields just weren’t
quite the diamond-dust I was expecting. A brief look at Mars didn’t look quite
right either, with a spike of flare on one side of the planet.
I had to wait a week
for some custom rings from Parallax to arrive, but when they did
I was able to mount the big Tele Vue up on my AP1200 for a proper evaluation.
Held rock steady, it took moments for me to do a star test and realise that the
NP-127 was out of collimation. It wasn’t badly
out of collimation, but just enough to make diffraction rings bunch up a little
on one side.
To cut a long story
short, the NP-127 was sent back to Tele Vue and eventually returned. Packed in
all the original materials it was like receiving a brand new one. I believe the
entire optics set had been replaced. So how was the scope in its fixed form?
Let’s find out ...
In
Use – Daytime
Like the optically
similar NP-101, the NP-127 works superbly as a terrestrial scope, with its
combination of high optical quality, perfectly flat and coma-free field and lack
of false colour. The view with a 40mm Pentax XW is sensationally wide and
bright and crisp. The definition and resolution, even at just 17x
magnification, is amazing. It makes a superb telephoto lens for nature
photography as well:
Cropped photo of a
pair of chilly Jackdaws, taken with NP-127.
Moon, out of
focus behind snowy branches.
In
Use – The Night Sky
General
Observing Notes
I did much of my
testing with the NP-127 mounted on the AP 1200. The result is laughably stable:
you can drum on the side of the focuser at high power without seeing the
slightest movement; perfect imaging focus can be obtained using the manual microfocuser, even at very large image scales, with no
electric focuser required.
Mounted like that I
could easily and quickly do a star test and a high-power check on Jupiter and
fortunately the collimation problem had been completely fixed. The star test
was now spot on.
Perfect focus is an
absolute snap, marked by the smallest touch on the focuser. That focuser
generally smooth and sweet and shift free.
You would expect the NP-127
to be a great deep-sky scope, but it turned out to be really good on planets
too, though you need short focal-length Eps to get the necessary high powers -
it has a focal length of just 660mm, but will usefully take 200x magnification
and more, so the 3-6mm Nagler zoom is ideal. At the other extreme, the NP-127
will deliver a four-degree true field with eyepieces that have the maximum 2”
field stop.
The only serious
niggle is lack of focus travel. TeleVue’s own 55mm
Plossl won’t quite come to focus (even in TVs own diagonal) – a bit of an
oversight, surely!?
Cool
Down
Cool-down
takes perhaps half an hour – slower than a smaller doublet, but faster than a
triplet of similar size. Until cooled, Venus looked a bit of a
mess with tube currents spoiling the view: the NP-127 has a lot more glass and
air to cool than an NP-101 and this shows, making it less ideal as a quick-look
scope.
Star
Test
The star
test, post fix, was excellent.
The
Moon
The Moon looks great
through the NP-127, with lots of fine detail a smaller APO doesn’t show and
with dense black shadows and cold greys: no false colour anywhere. Again, the
difference to a smaller telescope is stark, even at lower powers. Rilles and domes and peaks and craterlets, subtle rays and
wrinkle ridges are just apparent when they wouldn’t be in a smaller telescope
(I compared my TV-76 to be sure).
Venus
Venus showed a
perfect, dazzling crescent, with a hint of the ashen light and some
indentations in the terminator due to the clouds (that Schroter
thought were mountains).
Mars
Even before fixing,
the NP-127 showed significant detail on Mars: as much as my TMB-175 on all but
the best nights. Again, I am reminded how much more powerful (in the general
sense) a 5” refractor like the NP-127 is than a 4”.
Jupiter
Jupiter (on a night of
good seeing first time out – lucky!) was a mass of whirls and spots and festoons;
the red spot jumped out at me.
Saturn
The NP-127 delivered
perfect, miniature Cassini-probe images of Saturn, with subtle banding on the
planet and the Cassini division clear and stark.
Deep
Sky
The NP-127 gave superb
views of every DSO I found. The Pleiades were gorgeous: sparkling jewels
embedded in nebulosity. The Orion nebula showed masses of detail and the Trapesium was an easy split. The Dumbbell Nebula stood out
from the background, surrounded by stars and looking almost 3D, likewise the
Ring Nebula. M81 was much brighter than usual and the open clusters in Auriga
just beautiful. M13 was lovely, with masses of pinpoint stars resolvable. For
most deep sky, I stuck with the 13mm Ethos - giving 52x and 1.9° true field - which
seems a perfect match for this telescope.
For
visual astronomy, the NP-127 is one of my favourite scopes and a wonderful
all-purpose instrument with much of the convenience and all the crisp wide
fields of a small APO, but with a lot more reach and resolving power.
In
Use – Astrophotography
If the NP-127 had been
designed mainly as a visual instrument, I would be very happy with it. However,
to see it in context, you need to realise that it is really an astrograph
moonlighting as a visual ‘scope.
Under my fairly dark
skies, it’s scarily easy to take nice photos with the NP-127. Stick a DSLR in
the back and even quite short exposures produce near-magazine quality images of
brighter DSOs when stacked. The combination of big aperture and short focal
length (so wide FOV) gives great results on M31, even without stacking. With a
top-quality CCD, careful setup and focusing and tracking on a stable mount like
the AP, I am sure it would produce images up there with the very best. Not
having to mess about with flatteners is a real bonus.
The I.S. focuser,
whilst not quite as good as a Feathertouch, is very
smooth and stable for supporting a heavy camera and the micro-focuser allows
very fine adjustment (it needs to, given the very small difference between in
and out of focus on the NP-127).
The only fly in the
ointment is that reduction of illumination towards the field edge, despite that
oversized Petzval lens, so it’s probably not going to cover a medium-format
sensor.
The
NP-127 makes a first-class astrograph for chips up to full-format, with a large
aperture, fast focal ratio and natively flat field.
Single frame of Orion taken prior to NP-127’s
repair, 1 minute at ISO 1600 with a Canon EOS 450D APS-C.
After repair, star images are better
off-axis in this single frame of the Pleaides, one minute at ISO 800 with a
Nikon D5100 APS-C.
Crop of prime-focus Moon through NP-127
– good despite small original image scale.
Summary
The NP-127 is one of
the very few telescopes out there that will do pretty much everything. It has
enough light grasp to start giving interesting views of DSOs, but still has a
wide enough FOV to view and image just about any object you can think of.
Almost uniquely among
imaging refractors, the NP-127 has the optical quality and resolution to see real planetary and Lunar detail. The now discontinued Pentax
125 EDF also had a very fast, flat field (another Petzval design), but even
Pentax admitted it wasn’t designed for high-power visual use; the new Takahashi
FSQ-130 is probably similar (and much more expensive).
Of course, this type
of versatility doesn’t come cheap from Tele Vue either and the NP-127 is an
expensive telescope by other standards, though you do get Tele Vue’s generally
superb build quality and (as I discovered) service to compensate.
Forgetting the
teething troubles I encountered, the NP-127 has very
few significant drawbacks. Perhaps the only serious ones are:
·
The OTA weight and the design of the rings
limit its portability somewhat, especially when compared to its smaller sibling,
the NP-101.
·
The focuser needs more travel and a
rotator would be a very useful addition.
The NP-127 is highly
recommended and could be a very satisfying only-scope.
