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Vixen NA 140 Neo-Achromat OTA



The Orion NA 140 Neo-Achromat, which is made by Vixen in Japan, is a discontinued item, so this review is intended solely as a reference to armatures that might be curious about them. It is possible that it may be offered as a Vixen in the future, but a search of US dealer’s web sites does not currently list this model. I bought this particular one on closeout pricing from Orion, but I don’t think I ever saw it in their catalog, and I know that I have not seen one advertised for sale on Astromart, so I suspect that they don’t exist in the US in very large quantities. Based on my inability to find much about them on the web, they might actually be rather scarce, maybe even rare. Perhaps this review will uncover some of the reasons for that.

In some ways, I owe the purchase of this scope to my Losmandy GM8 mount. I love the mount so much that it bothered me to see it sitting empty. I sold the MN61 that I had on it over a year ago. I figured that I needed to get something on top of it, and I wanted that something to be another good quality, medium aperture, short to medium focal length scope. Some of the Mak Cass scopes in the 6 to 7 inch range just have way too long of focal lengths to make them good for all around use, and I wanted to keep focal length to 1200mm or less.

I was missing some of the MN61’s attributes. My NexStar 11 does great on deep sky objects, and on planets when the skies are VERY stable, but on many nights, the little MN61 did as well on planetary performance because it just wasn’t affected as much by poor seeing typical of my area. It also offered a wide field of view that is utterly unattainable with the N11. In addition, double stars were much more pleasing in the smaller scope… There were certain qualities of the MN61 that I did not like… First, the eyepiece was often in an awkward position. True rotating tube rings would solve this problem. Light throughput seemed low. This could be attributable to the fact that my MN61 was an older OTA with less than great coatings. Overall, though, I missed all of the important positive qualities. I started looking for another MN61, an MN68, or MN71. MN61s are not difficult to find used, but the others are. I have owned a couple of 6” achromats, and was also considering them. I considered the Meade and 6” ED scope, but they are hard to find new. Additionally, these are f/9 instruments, and I was worried about poor viewing position at zenith because of the long tubes, and the inability to produce really wide fields of view. I also considered the 6” achromat with a Chromacorr unit, but my reservations were around overall cost, still kind of longish focal length and low flexibility because of having to use 1.25 eyepieces as recommended with the Chromacorr), and quality of the underlying refractor optics.

Why a NA 140??? In truth, it was kind of an impulse buy. I stumbled upon it on the Orion web page by following a link to their bargain/closeout page… I didn’t even know that this scope was ever made, and could find out almost nothing about it on the web. There were several reviews on the smaller NA 120, but nada on the NA 140. Reviews were somewhat mixed, with everyone agreeing that the NA was no APO, but no one seemed to say that they were bad… Could this be a reasonable tradeoff between the various factors I was trying to take into consideration?

I bought the OTA only… Included with the OTA were metal lens cover, mounting rings with vinyl carrying handle, and a 50mm finder and bracket. The only thing that was not included (besides the mount, of course) was the 2” visual accessory adaptor. The standard back accepts 1.25” accessories, and there is a rather complex drawing that showed all the possible combinations of extender tubes, threaded adapters, and reducers that might be required for different configurations such as straight through visual, visual with diagonal (reverse the tube used to hold eyepiece for straight through viewing and insert diagonal into short end, and so on) photographic, and CCD work. While I will only probably ever use the 2” back with a diagonal, it did show me that this telescope system could be easily configured for photo or CCD work. The fit and finish of all parts was excellent, and there was a nice feel of quality to the telescope. The focuser is smooth and allows very fine movement. It is a little tight, but it will probably loosen with use, and because I use heavy 2” eyepieces, maybe tight is better. All of my eyepieces came to focus with room to spare. This included several Nagler T4’s, Radians, Plossls, and a few odd-balls. Weight is low, and the OTA is very easy to handle, much more so than the 6” achromats that I have owned in the past. Not that it should matter, but this is a particularly handsome OTA. It has a wonderful proportion that gives it a very cool look. Of course this doesn’t affect performance, but it does garner comment. The 50mm finder is really good, certainly one of the better finders I have owned. It could almost act as a tiny stand-alone scope.

I mounted the OTA on my trusted and favored Losmandy GM8, and I will say that the combination is a perfect one. The OTA is so short that I can observe even at zenith while sitting on a low stool. The combo is VERY solid even in minor wind gusts. The lightweight of the OTA makes it possible to move the mount from inside to outside (minus OTA of course) with the weights still on the declination shaft. OK, barely manageable, but possible (did I mention that I am 6’ tall, weigh 190 pounds, and am a Marine Corp Veteran? Don’t try this if you were in the Navy).

OK, enough of the yak, yak… You really want to know how the Neo-Achromat optics performed, eh? With all of the hype around high-end APO scopes, and the soaring prices, everyone wants to find reasonable substitutes. Even used APO scopes command unearthly prices. I feel that I am fairly well off financially compared to many armatures, but value for dollar DOES matter to me, and while I would love to have a 6” APO, I guess in the end, I am just too cheap to pay the astronomical prices for a used one. Would the NA 140 fill the bill??? Well, yes and no. I think it did fill the bill for me, but if color correction is your ultimate measure of telescope performance, the NA 140 surely can’t be considered as a viable substitute for a true mega dollar APO.

The OTA spec lists it as 140mm of aperture at f/5.7. That makes a focal length of 800mm. This is REALLY fast for a larger aperture refractor. With a 35mm Panoptic, I can get 23x with an almost 3 degree field of view. This alone makes telescope quite interesting. No point going lower because the exit pupil here is already at 7mm.

Collimation out of the box was dead on. Star testing on an in-focus star showed optics that appeared to be excellent. At 160x using a 5mm Radian, the airy disk on Mag 2 stars were just about perfect; a tiny dot, with a fine, VERY dim first diffraction ring. No violet color was evident. The NA 140 presented maybe the cleanest in-focus airy disk images I that I have ever gotten out of any telescope I have ever owned, including my MN61 (though the difference here was small and due perhaps only to the fact that the first diffraction ring in the MN 61 was a bit brighter, as optical theory predicts that it should be). The field is very wide and fairly flat, and with my 22mm Nagler, the view is awesome, though similar to the MN61 I used to own. The MN61 has a 900mm focal length, compared to the 800mm for the NA 140, so magnifications would be similar, making this a pretty fair comparison, though it is important to mention that all comparison being made here are from my memory, as I no longer own the MN61.

Yes, there is chromatic aberration visible on very bright stars. More than “just a little” but much less than the 150mm f/8 refractors I have owned. Considering that this is a f5.7 instrument, there really isn’t anything else in the non-APO market to compare it to. The field is not flooded with violet/blue as with the 150mm f/8 achromats, and indeed, I found that the color just wasn’t really a bother. Below 1st magnitude, chromatic aberration ceases to be noticeable.

Large refractors are considered by many to be the best overall instruments for use on planets where perfect seeing conditions are not available. I have had several people tell me that even with the secondary color in their 6” achromats, they still prefer them to larger reflectors or SCTs for planetary observing. Popular opinion is that the excellent contrast of a mid-aperture refractor allows them perform well on many nights where seeing just won’t allow large reflectors or compound scopes to show superior images.

So how did the NA 140 do on Jupiter? Quite well, actually. OK, everyone is probably asking about false color, and yes, there is some. Surrounding the planet is a moderately bright deep violet halo. It does not extend far from the planet, and it is probably just what Vixen says in their brochure on the web: Vixen states that a Neo-Achromat can reduce color to one third of what you would observe with a similar aperture achromat. This pretty much coincides with my own observation. There is much less color than what I have seen using 6” achromats, but it is clearly noticeable. Also, I will mention that while the color is easily visible against the background sky, the color doesn’t seem to bleed over to the actual planetary disk. At high power with my large achromats, the whole planet would show a violet wash across the disk at high power, which was certainly obscuring some detail. I just really didn’t see this on the NA 140. Disk detail was very good to excellent for a 5.5” aperture, and contrast was very high.

I do need to say that on the same night, in a few very brief moments of excellent seeing, my Nexstar 11 clearly showed more detail on Jupiter’s disk. Oddly though, in the N11, the moons of Jupiter were more like tiny blobs, while in the NA 140, they were stunning small, hard edged, different sized disks with hints of color differences between them. I don’t think I have every seen them better. In obstructed instruments, their edges always seem to have a little fuzz to them (blobs on most nights with the N11), but with the NA 140, the were suddenly tiny new worlds! I was able to us my 5mm Radian with an inexpensive barlow for a total of 320x, and I was impressed by the ability of this scope to hold high magnification well. While no additional detail was seen over 200x (barlowed 8mm Radian), the image remained fairly bright and sharp.

Against the MN61, memory suggests that the MN61 might be the winner here by a slim margin, but my particular (and older model) MN61 started to dim at around 250x. I did not do direct comparison, but my memory suggest that the MN61 was a wee bit sharper, almost equal in contrast, and of course, totally color free. My sky is rarely steady enough to get great planetary observing results unless the planet is almost directly overhead. Jupiter is getting low in the sky after dark for me now, so perhaps if I would have had the opportunity to view Jupiter at zenith in a direct comparison, it would improve my perception of the NA 140 vs. the MN61. It might have been a closer call than memory suggests. Jupiter did look pretty darned good.

I have had limited experience using the NA 140 on Deep Sky, but I would say that what little I have seen says that here the NA140 might have a small edge over the MN61. Excellent baffling and no obstruction result in superb contrast for the NA 140. A few nights ago, I caught M13 at zenith, and there was some star resolution across the core. At low power, it stood out quite well against the background in my medium light polluted skies. My memory says that my MN61 offered a very similar view, but without having quite the contrast, and maybe not quite the amount of stars detected, though memory may fail me here. For comparison sake only, the NexStar 11 explodes M13 like Luke Skywalker did the Deathstar. You can stand right down in the middle. The same comments would apply to M57, which when viewed with a 17mm Nagler through the NA 140, was splendid. The NA 140 made it stand out rather vividly, and with the surrounding star field, the view was surreal. The views are more aesthetically pleasing than in my Nexstar 11, but there really is was no comparison to the larger scope in terms of absolute performance except with the aesthetic quality of the star images. In my N11, the M57 starts to show true detail. Still, using the larger scope, I am limited to including the area just around the nebula even using my lowest power eyepiece (Televue 40mm WideField) where with the 35mm Panoptic in the NA 140, it seems like I can fit half the constellation in the field of view!!! Seeing M57 in that context is a wondrous experience.

Two nights ago (June 7) I had the chance to do some lunar observing with all three of my current scopes side by side. My “Small” scope is an Orion 127 Mak, which I bought used. My large scope is my Nexstar 11 with good optics (1/4 wave, maybe slightly better). No surprise that the order of performance was exactly what one would expect, with the small Mak putting in the “poorest” showing, and the N11 doing best.

The Mak showed contrast loss by way of obscured detail in faint surface features. While viewing though the 127 Mak, I could often perceive that a surface MIGHT have some roughness (which is the way I compare contrast), while I could actually see that roughness clearly in the NA 140. Faint craters that would be clearly visible in the NA 140 were often only hinted at in the 127, and maybe only because I knew exactly where to look because I viewed the area first with the refractor. When I would concentrate on an area with the StarMax 127 and change to the NA 140, everything I saw in the 127 Mak would be quickly visible in the 140, but when studying areas first in the NA 140 first, then changing to the 127 Mak, I would struggle to see the same detail in the Mak. More importantly, the image had more dynamic range of contrast in the refractor, with more distinct graduations of gray and silver seen in the NA 140 than in the smaller Mak. Everything just looked far more “Alive” in the refractor.

Against the N11 there was about an equal amount of difference, only with the larger scope performing better. Get a second or two of good seeing, and the N11 would show roughness where the NA 140 only hinted at it, and overall contrast dynamic range was better in the larger scope. It is important to say that this only happened from moment to moment because of seeing conditions. Patience in the N11 always brought out more detail, but the price was the time spent waiting for those moments of stable seeing, and then the extra detail would only be visible for an instant. Resolution though, was always better in the larger scope. Optical physics theory wins again.

To be fair, I have to say that the Orion 127mm Mak is by itself, the best small scope that I have ever owned. It would be my hands down choice of all the small scopes (total physical dimension) I have ever looked through, which have been mostly reflectors and fast refractors, and nothing exotic. If I were limited to spending under $500 (OTA sells for $400 new) this would be my first choice. The fact that it didn’t do quite as well as an unobstructed OTA that costs 5 times as much and is 10% larger in aperture shouldn’t be a surprise. I must say that mine, acquired used for $300, startled me with its optical quality and performance. I doubt that they can all be this good.

Going exclusively from memory and extrapolating from my experience with my own MN61, I would say that a newer MN61 with improved coatings would be equal to, or maybe even slightly better than the Vixen NA 140 in planetary performance, and a match in most other comparisons, and at a little over half the price. This brings me back to the remark in my opening paragraph that we might uncover the reason why NA 140s are not common in the US. That reason might be because excellent quality Mak Newts ARE commonly available, and at a little over half the price of the NA 140. Just get one with high transmission/reflectivity coatings.

That being said, there is something intangible about the quality of views through a good refractor, and if you can afford one (See my RANTING at the end of review), I would classify the NA 140 as at least a very good refractor. Excellent would be my thinking if you weren’t disturbed by the small (but distinct) chromatic aberration on bright objects. Stars are tiny, tiny points making double star work fun for me (never been fun before). Star color contrast is more evident than in any other scope I have ever owned, though the big f/8 achromats I have owned (2) were also noteworthy in their ability to show faint color contrast in doubles. Refractors just seem superior when looking for these subtle color differences to almost everything else. The NA 140’s wide field, low power views are even wider than those on the MN61, and I can push the magnification quite high and still maintain reasonable image brightness. The viewing position is more comfortable than I could achieve with the MN61. If you have read any of my other reviews, you will know that observing position is VERY important to me, especially in winter, when I like to stay seated with a blanket over my lap. Its short focal length also makes for a relatively compact and light scope, which is a breeze to handle. My high quality, mid-aperture OTA craving has been largely satisfied.

p.s.

I would also repeat the almost exact same closing remark here that I did in my MN61 review. It is my opinion that these kinds of scopes don’t compare well to much larger telescope like the Nexstar 11 in terms of all around performance. While large SCTs (>9”) might not do anything with excellence, good ones do nothing badly; go MUCH deeper on deep sky objects (which constitutes the majority of my observing) and when viewing conditions are excellent, the larger scopes will excel at HIGH POWER planetary and lunar observing. If you don’t already have a good quality EQ mount, the total package cost of the NA 140 OTA and mount might make a larger SCT or large dob on driven platform a better all around instrument. If size and weight/transportability are factors, or if you want a no-maintenance, ultra fast refractor with excellent (non-apo) performance then the NA 140 might be a very attractive placeholder for the AP 155 in your future. I like my NA 140 enough that it joins my “Not for Sale” inventory along side of my GM8, and will be the permanent OTA for that mount. But if I didn’t have a spare high quality mount and money was a little scarcer around my house, I wouldn’t have bought this scope or another MN61… Provocative comment??? Read on….

RANTING BEGINGS HERE!!!

By way of qualifying my comment regarding the N11 doing well at HIGH POWER observing, I will say that in most cases, even when seeing is average, it is rare for me to ever see LESS planetary detail with the N11 than with smaller scopes. If I keep magnification equal, and at around 180x, which is the most I can routinely use anyway, the N11 is every bit as sharp under my typical seeing conditions as the smaller scopes are. When skies are stable, and high power observing becomes practical, the difference in image brightness allows me to push 350x or 400x with the N11, while the smaller scopes may top out at much less than this because the image just gets too dim. I am 51 years old, and my eyes aren’t what they used to be, but my lifelong experience has been similar. Image brightness improves contrast. Larger scopes generate multiple times the image brightness of smaller scopes.

SEEING is the biggest culprit in the inability of larger SCTs to perform well (assuming exact collimation and good optical quality), but even when seeing is average, my experience in numerous side by side comparisons is that reasonably good 10” or 11” SCT will just about NEVER show less than the same planetary detail that a 6” Mak Newt or a 5.5” Neo Achromat will show under the same conditions and typical useful magnifications. I have seen good 8” SCTs that would outperform or equal the scopes mentioned here on planetary and lunar performance, and would easily outperform them on deep sky. If I could get even a 1.5-degree field of view out of my NexStar 11, I might not bother with mid-aperture scopes at all. When equatorially mounted on a good mount like the GM8, these mid-aperture scopes are as much trouble to transport and to set up as a larger SCT, less comfortable/convenient to use, expensive per inch of aperture, and inferior in most deep sky observing. In short, I remain a staunch advocate of larger aperture SCTs as being a great value proposition, often getting the amateur astronomer more all around benefit for less money than almost anything else in the marketplace…

I only go on this tirade because prices for small refractors are at insane levels, with even “Premium” 4 inch ACHROMATS selling for near $1000, and anything saying APO on the label selling for twice that sum without a mount!!! Believe me, in a side by side comparison between a small high quality (read EXPENSIVE here) 4” refractor against a SCT with twice the aperture of reasonable quality, my bet is that the larger SCT would outperform the smaller scope on pretty much every target, pretty much every time. 8” SCTs revolutionized armature astronomy 30 years ago, and the reason they did was because they offered far more performance than the long focus 3” refractors (the APOs of the day), at a very competitive price. I for one don’t think that this situation has really changed that much, even after 30 years and the reduction of 6 f/ stops in the refractors. If anything, the proposition has even gotten stronger, with fully computerized 8” SCTs being available for less than $1500!!! It’s crazy. Really.

I hope that these remarks generate discussion, because I fear that many amateurs expect some magical performance from these high priced small and mid-sized refractors. My NA 140 is a really nice refractor, and I am happy to own one, but I want to make newcomers to the hobby aware that there is no magic dust. With the Mars close approach, I sense that we will see a flood of new amateurs entering our ranks, and they shouldn’t be led to believe that they have to spend $3000 on a high end 4” refractor and mount to see the big show. Many of these people would be perhaps better served by a good all-purpose scope like an 8” SCT. After Mars, and between the gas giant showings, there is a galaxy full of interesting targets that get even more interesting when viewed through larger scopes. It is my opinion that with their decent light gathering, excellent ergonomics, portability, ease of use, all around versatility, and reasonable price, there is still nothing in the marketplace that can challenge the mid-sized SCT (8” to 10”) as perhaps the greatest all around telescope format available today.

RANTING ENDS HERE….

Your turn….

My regards, and remember, it’s not what you look though, its what you can SEE that makes this a magical hobby.

Ciao, my friends.


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