Tele Vue NP127 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 NP127.
At A Glance
Tele Vue NP127 IS
Data from Tele Vue.
Design and Build
The NP127 has much in common with Tele Vue’s other refractors, past and present, including the Genesis, Renaissance and NP101; except of course that it’s bigger!
Originally, you could get the NP127 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.
The NP127 has a four-element (quadruplet) optical system, known as a Petzval, a system it shares with the NP101.
For full details of the Petzval design, see the NP101 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 NP127 has very good correction for CA, but with an F ratio of just 5.2 – faster than the NP101’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 NP127 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 NP127 is a five inch APO and a three inch APO in one tube).
Like all of Tele Vue’s scopes, the NP127 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.
NP127 objective fills the tube.
Petzval flattener/reducer lens at the front of the focuser.
The NP127’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 NP127 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 NP127 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 NP127, with its heavy focuser and stubby lens cell. More recent versions have a longer dew-shield and look more balanced.
NP127 is a big, heavy scope compared to other Tele Vues.
NP127’s fancy, transparent dew-cap.
In order to support large cameras, the NP127 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.
The NP127 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 NP127, with bigger bearings and a wider yoke. The head goes on a standard Gibraltar mount.
Rings are not included with the price of the NP127. 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 NP127 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.
NP127 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.
NP127 ships in a quality hard case.
The NP127 comes with the same quality hard case they used to use for the NP101 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 NP127 (which some 3rd party Eps, such as Pentax XWs, may not).
I bought my NP127 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 NP101 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 NP127 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 NP127 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 NP101, the NP127 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 NP127.
Moon, out of focus behind snowy branches.
In Use – The Night Sky
General Observing Notes
I did much of my testing with the NP127 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 NP127 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 NP127 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 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 NP127 has a lot more glass and air to cool than an NP101 and this shows, making it less ideal as a quick-look scope.
The star test, post fix, was excellent.
The Moon looks great through the NP127, 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 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).
Even before fixing, the NP127 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 NP127 is than a 4”.
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.
The NP127 delivered perfect, miniature Cassini-probe images of Saturn, with subtle banding on the planet and the Cassini division clear and stark.
The NP127 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 NP127 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 NP127 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 NP127. 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 NP127).
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 NP127 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 NP127’s repair – still good for an unprocessed image with a cheap DSLR (EOS450D).
Crop of prime-focus Moon through NP127 – good despite small original image scale.
The NP127 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 NP127 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 NP127 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 NP127 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 brother, the NP101.
· The focuser needs more travel and a rotator would be a very useful addition.
The NP127 is highly recommended and could be a very satisfying only-scope.