Vixen NLV 20mm


Let me confess that I have a bit of a soft spot for Vixen – a company deeply rooted in the astronomy industry, and the manufacturer of the first Plossl I ever bought. That beautifully crafted Japanese-made glass completely transformed the performance of my first telescope, and to this day I haven’t yet discovered a finer example (read: Tele Vue don’t cover that particular focal length). With that in mind, I’ve been careful to give the Vixen NLV 20mm a fair test. As far as I can track down, Vixen first introduced their Lanthanum range (since known as LV and NLV) in 1994, and whilst the principal concept behind these eyepieces – namely the use of Lanthanum-doped glass – hasn’t changed, the focal lengths, housing, and perhaps coatings have undergone a few revisions. The NLV are quite different in appearance from their ancestors; indeed nothing else on the market, regardless of manufacturer, look quite like them. But how does the 20mm perform, and does it deserve a spot in your collection?

Let’s start with the name. Lanthanum is a rare earth metal commonly employed in the production of optical glass. More specifically, the glass is doped with small quantities of lanthanum oxide, and the result is a high refractive index, enabling relatively flat elements with higher power. Since eyepieces contain sets of elements (in the case of the NLV 20mm, that would be 7 in total) different glasses are employed throughout the optical assembly to control aberrations. This is important to bear in mind, because whilst the NLVs, LVs and earlier versions of the Vixen Lanthanums do contain some of the element they’re named for, the use of Lanthanum doesn’t necessitate that the eyepiece is better, or even good. But despite their suggestion that the use of “high-grade lanthanum” helps to obtain a “sharp field of view with high contrast”, it wouldn’t be fair to tar Vixen with the same ‘buzzword abuse’ brush as the truly awful offenders currently flooding with market with “apochromats”. Lanthanum is used by numerous optical manufacturers, and not just in astronomy, so it’s undoubtedly useful, but let’s not take it to be a selling point. Sure it sounds cool, but the only way to determine the performance of the NLV 20mm is going to be a direct test!


If you’ve read my other eyepiece reviews, however, you’ll know we can’t get to that just yet. First, the build and aesthetics. My initial impression upon handling the eyepiece was very good. The solid construction and surprisingly low weight (about 130 grams) give it a unique feel, altogether pleasant, and I found the groove on the 1.25” barrel to be nicely snag-free. The filter thread and blackening are of a high standard, and the overall quality is excellent. But now we come to the ugly, plastic housing, and what I’m about to say will probably shock you: I think this is a fantastic looking eyepiece. No, really. The use of plastic in the body has resulted in a lightweight eyepiece, but it’s notlightweight’. Rather, it feels perfectly well built – just light at the same time. And its clean, off-silver livery with the narrow strip of colour evokes a strange sensation of science-fiction nostalgia in me, as though it belongs on Picard’s USS Enterprise.

When I’m not reminded of Star Trek, I enjoy the NLV’s charming simplicity – a salute to the design philosophy of many classic Japanese telescopes. Even the plastic thread on the twist-up eyecup – hardly the smoothest ever made – just works as far as it needs to, without complicating things. Granted, it only has two positions (up or down) but in all my tests I found that they’re the only two needed. I do believe my opinion on the aesthetic of the NLV will be unpopular; in fact many reviews of other focal lengths in the range, some from observers I greatly respect, have panned the housing as looking and feeling cheap. I thoroughly disagree, but would encourage the reader to seek one out in the flesh and have a closer look. My photos don’t really do it justice!


Without an observing plan I dropped the NLV 20mm into the back of my 6” F/10 SCT and focussed down on an arbitrary field of stars in Taurus. Though I wasn’t entirely sure of what to expect, I was skeptical of the lanthanum sales pitch, So you can probably imagine my surprise when I was greeted with a remarkably high-contrast image. The contrast struck me immediately, coming joint first with the wonderful viewing comfort. The NLV 20mm delivers its promised 50 degree apparent field at the controlled 20mm eye-relief intended for its design, without kidney beaning, and resting on the extended eyecup allows complete appreciation of the image, right to the sharp field stop. Of course with the eyecup down, the characteristic long eye-relief is ideal for spectacle wearers. I’ve really only encountered such a combination of contrast and eye-relief a few times before at this focal length; notably with the 20mm Pentax XW and, more recently, the 17.3mm Tele Vue Delos. The 18mm Tele Vue Radian also deserves a mention. Considering the high pedigree of such eyepieces, I believe the Vixen NLV is in very good company for its price.

The NLV goes toe-to-toe with my 20mm Tele Vue Plossl for contrast, but with about 6mm more eye-relief, and as I would discover later in my test, better performance with fast optics. To say the views were crisp would be an understatement – lunar and planetary details were razor sharp, and in my F/6 and F/7.5 ED refractors, many a fine galactic cluster threw pin-point, colourful stars to the edge of the field. I measured the tiniest touch of pincushion distortion, as well as minute traces of lateral colour, but they were no more intrusive than that seen in the wide-angle alternatives at twice the price. Angular distortion on the other hand, was constrained to the furthest extremities of the field edge, and hard to detect even in the defocussed test at F/6. In sum, this ocular is an optical gem.


Vixen are renowned for doing a limited number of things well. Their product line evolves slowly, but excepting a few outsourced one-offs, it epitomises the “if it ain’t broke…” attitude. The NLV 20mm, one of a long-standing family of eyepieces, delivers true Japanese optical quality at a fair price, and it certainly ain’t broke. It may not be the last 20mm eyepiece you buy, but if you’ve only ever owned a stock Plossl or Kellner, I dare say it will enhance your experience even more than my first Plossl did over the Huygens I started with. Unless you already own the aforementioned Pentax or Tele Vue eyepieces, I would thoroughly recommend considering the NLV 20mm. Oh, and did I mention that it looks great?

Make it so, Number One!