Telescope Reviews: 42mm Nikon Binocular Duel

42mm Nikon Binocular Duel

Duel, implying as it does a winner and a loser, is not perhaps the right term for this report, which compares two of the finest binoculars available for handheld astronomical observation. Most observers would be thrilled to own either instrument, and a final choice between the two is likely to be based on subjective factors. Still, decisions have to be made and if this report assists anyone in his or her search for their next binocular my purpose here will be served.

Tuesday afternoon (June 22, 2004) I received a call from an observing friend who owns a pair of Nikon 10x42mm SE binoculars -- not to mention a fine 20-acre, dark-sky site with a fully-appointed roll-off roof observatory in Linn County, Kansas (named the "Land of OZ Observatory"). The radar looks great, says Ron, I think this is the night. And thus, the Nikon 8x42mm LX versus Nikon 10x42mm SE binocular duel came to pass.

Why Would Anyone Spend THAT Much Money for Small Binoculars?

For those not familiar with Nikon's SE and LX binocular lines: these are what the manufacturer describes as "premier optics." The optical performance is indeed among the best (if not THE best) available in the 32mm/42mm class of binocular. The prices are also "premier" around $800 for the SE 10x42s and $900 for the LX 8x42s (street prices).

When I first encountered a pair of Nikon SE binoculars, I was astonished by the price. I had a look through them. They felt good and the view did seem nice, but I couldn't imagine spending that much money on a pair of small binoculars. Instead, I bought 10x50mm Nikon Lookout IVs, which cost about $125.

As I gained experience as an observer, however, I started noticing problems with the Lookout IVs. Away from the center of the FOV, stars were not sharp. Toward the edges they actually became distorted. I found myself frequently refocusing the binoculars and adjusting the right diopter control. The roll-up eyecups were also a pain. They were difficult to roll up and down. In the up position I couldn't see the full field wearing glasses. In the down position friends without glasses couldn't use them effectively due to blackouts in field of view.

I'm going to spend another minute on the focus issue because an important element of the problem can easily checked while examining binoculars in the shop. Please see the Lookout IV close-up picture below. The Nikon Lookout IVs focus with a central knob that moves the eyepieces in or out. Most most porro-prism binoculars focus this way. The eyepiece assemblies are connected to the central post with short arms. These arms have a certain amount of spring or play to them. A small amount of pressure on either eyepiece moves it up or down. As a result, it is quite easy to alter the focus by the way you hold the binoculars up to your face.

As obvious as this may seem, it isn't really that apparent at first. In fact, it took several years of continuous use before I realized that part of the frustration I had with focusing had to do with the way I held the instrument. To my way of thinking, this is a serious design flaw. Whenever I examine a binocular, one of the first things I check is the stiffness of the eyepiece armatures. If they exhibit more than the slightest amount of flex, they are unsuitable. An important feature of the LX series, and of roof prism binoculars in general, is that they focus internally. The eyepiece assemblies don't move in and out. This is no small advantage when it comes to making a rugged, smoothly performing instrument.

Another thing to notice in the close-up on the Nikon Lookout IVs is the black electrical tape on the diopter control. When I complained to my friend at the birding store about constantly fiddling with the diopter control he grinned and said I should adjust it and then use electrical tape to lock it in place. After slapping myself on the forehead (why hadn't I thought of that?), I followed his advice and significantly improved the instrument at practically no expense.

Although I've been critical of the Lookout IVs, they're not a bad value - I did a lot of enjoyable astronomy with them. But after four years of use it occurred to me that I had spent more time observing with my inexpensive 10x50s than with five telescopes I owned during that period combined. I won't mention how much money was "invested" in those instruments (or my fine collection of Tele Vue eyepieces). Suffice it to say the amount I've spent on telescopes since buying the Lookout IVs makes $800 - $900 for top quality handheld binoculars appear a lot more reasonable.

Why 42mm Instead of 50mm?

Although conventional wisdom holds that 10x50mm binoculars are the optimum for handheld astronomy, premium quality 10x50mm instruments are scarce. The reason is that the handheld binocular market is driven by birders, hunters, and sports enthusiasts who observe during daylight hours when eye pupils rarely if ever dilate to the 5mm exit pupil size of 10x50 binoculars. (Exit pupil = objective aperture divided by magnification: 50mm / 10x = 5mm.) Larger exit pupils cause objects to appear brighter in the instrument until the exit pupil becomes larger than the pupil of your eye. After this point, additional light does not enter your eye and so the apparent brightness of objects in the field of view does not increase.

Since your pupils are smaller during daylight, a smaller binocular can provides as much usable light as a larger instrument at the same magnification. Smaller, lighter binoculars are preferred, thus 32mm and 42mm binos are more popular with daytime users. In fact, even 42mm instruments are frequently considered overkill.

The Contestants

The Nikon SE binoculars are more or less the darlings of the birding world. It's not hard to understand why: they are light, comfortable to hold, amazingly sharp and bright, and competitively priced. More than a few reviewers have concluded they are the best instrument available in their class. And they are often touted for astronomical observation (with good reason!).

Optically, the LX binoculars are even more highly regarded by some reviewers, but they are encountered less frequently in astronomy. For one thing, they're more expensive. In the 42mm size, they cost about $100 more. They are also heavier than the 10x42 SEs by almost 10 ounces, which is not a small amount for a handheld instrument. But the LX binoculars offer significant features not provided by the SE line.

The SE binoculars utilize porro prisms, while the LX binoculars utilize roof prisms. Roof prisms are more complex, less-light efficient, and more expensive to manufacture than porro prisms. However, roof prisms provide a more compact light path (straight through instead of Z shaped) and are more rugged (so less subject to collimation problems). Inexpensive to moderately priced porro prism binoculars provide better performance dollar for dollar than roof prism models. This is not the case for premium binoculars. When built to high standards, roof prisms at least equal porro prisms in performance (more on this below). Most premium quality handheld binoculars utilize roof prisms. The Nikon SE binoculars are a notable exception to this rule.

LX binoculars are waterproof. As previously mentioned, roof prisms permit internal focusing mechanisms so the eyepieces do not move during focusing. This makes it easier to seal the instrument. The LXs also have twist-up eyecups, which are a substantial improvement over rollup designs. Twist up eyecups enable observers to set precisely the amount of eye relief required for comfortable viewing and are easily adjusted for different observers. The LX also features a locking right diopter mechanism which eliminates any issues with the right eyepiece changing focus. (Worth the $100 price difference by itself as far as I'm concerned.)

Let the Games Begin

The following remarks are based on side by side comparisons made on June 22, 2004 from a dark sky site in Linn County, Kansas with a naked-eye limiting magnitude of approximately 6.4. The night was transparent, reasonably steady, and the dew was manageable -- a rarity in the Midwest in June. The instruments used were Nikon 10x42mm SE and Nikon 8x42mm LX binoculars. Ideally, I would have compared 10x42 SE with 10x42 LX binoculars. In fact, my friend at the birding store is ordering 10x42 LX binoculars to carry in stock. We plan to spend an evening comparing the 10x42 LX and SEs, as well as the 8x32 SE and 10x32 LXs.

When I first handled a 10x42mm Nikon SE, I was surprised by how comfortable it was to hold -- compared with other binoculars I had used. Then I tried an LX. Frankly, it's the most comfortable binocular I've ever used. (One of the reasons I chose the LX over the SE.) Refer to the picture below showing both instruments.

The SE binoculars are significantly wider than the LX binoculars due to the porro prism design, which results in the familiar "Z" shape of traditional binoculars (the objective ends being farther apart than the eyepieces). When gripping the SE barrels, a user's hands are spaced apart. By comparison, when holding the LX barrels (which are inline and much closer together) the user's hands fold together and support one another (a sort of triangle effect). For me this is a much more comfortable position. Depending on the size of your hands and what feels comfortable to you, you may prefer the porro-prism shape.

I must say that other roof-prism binoculars I have tried don't feel as comfortable to me as the LXs. The Nikon design somehow feels more natural than other roof-prism binoculars I have handled.

The LX twist-up eyecups make it possible to rest the binoculars directly on your eyeglasses or cheekbones, which is a considerable help in stabilizing them. The SEs have standard rollup eyecups. When the SE eyecups are rolled up, I can't see the entire field. When they're rolled down, I have to hold the instrument away from my glasses to obtain the correct eye relief. In this position, they're nearly impossible to hold steady. Except when testing edge sharpness below, I resorted to leaving the eyecups rolled up to steady the view. Now I suppose an eyeglass wearer like myself could rig up some sort of eyecup adjustment for the SE, but after spending $800 for the binocular, the psychology fiddling with the eyecups is wrong. Way wrong!

Although the additional weight of the LX appears to make it less user-friendly, in my opinion the design more than compensates for the additional 10 ounces.

Chromatic Aberration

Chromatic aberration, CA for short, is an optical defect resulting in yellowish or purplish halos that appear around the edges of objects in the field of view. The defect is a characteristic of refractors and is more prevalent in faster optical systems. Premium refractors reduce CA to negligible, possibly undetectable levels. Binoculars are essentially extremely fast refractors and even premium instruments often exhibit CA to some extent.

I can tell you from personal experience that it's unsettling to discover CA in one's brand-new, $900 binocular! However, after looking into the issue and using the LX binoculars for a few months I've noticed several things about CA. First, a lot of people just don't see it. They'll tell you that a particular binocular exhibits no CA. However, I have yet to see a reasonably compact handheld design that doesn't. (I have not had the pleasure to test a Zeiss 7x42 BGA/T Dialyt, yet, and look forward to doing so as it reportedly exhibits no CA.)

Second, as several kindly souls on the CloudyNights forum suggested when I was obsessing about CA in my new LX binos, it can be significantly reduced by adjusting the inter-ocular distance, focusing carefully, and centering the subject. Also, CA in LX binos is noticeable only in bright lighting and on high-contrast subjects. Once you become familiar with the instrument, it is easy to control and ignore.

For astronomy use, it is a non-issue. Even while observing the full moon, the effect is nearly invisible. It's most noticeable during daylight when looking at dark objects surrounded by a light background. At night, with a bright object surrounded by the dark sky, it's darn hard to see. Frankly, my Tele Vue 101 refractor exhibits about the same amount of CA on the limb of the full moon.

The difference in CA between Nikon LX and SE binoculars is zip. They both exhibit it to the same extent and it can be controlled in both instruments with the same techniques.

Sharpness

I got a surprise when comparing sharpness between the 10x42 SE and 8x42 LX binos. I did not expect to see much difference between the two, but found that the 8x42mm LXs are sharper off-axis than the 10x42mm SEs. Neither is sharp to the edge of the field. But stars near the outer edge of the 8x42 LX binos are smaller and less distorted than in the 10x42 SE binos.

To try to quantify this, I observed Rho (5) Ophichi which is a 4.98 mag B2V spectrum star a bit above Antares in Scorpius. The star is flanked by two companions that are separated from it by about 2.5 minutes. I centered Rho in the field of both instruments, focused carefully, and then moved the star to the edge of the field of view watching to see when I could no longer distinguish the companion nearer the edge of the field. With the SEs, I found that at about 75-80% of the field, I lost sight of the companion star. The LXs held the companion out to about 90% of the FOV. At any rate, observably closer to the edge.

The LX actually has a wider FOV than the SE -- 7 degrees versus 6 degrees. I hadn't anticipated that even with a wider field the LX would still be sharper to the edge than the SE. I'm not sure whether to attribute the difference to magnification alone and look forward to comparing the 10x LX with the 10x SE at a later date.

I should also say that when I wasn't deliberately checking edge performance, the difference wasn't that noticeable. In my opinion, edge performance is not a reason to choose the LX over the SE -- the difference isn't that great. However, if you prefer a wider field, rest assured you won't be sacrificing edge performance by choosing the LX.

Another interesting point about edge performance is that it is extremely difficult to judge during daylight. During day time use, both instruments appear to be sharp to the edge. They are frequently described as such in test reports. Pinpoint light sources on a dark background, however, is a far more stringent optical test.

Apparent Field of View

The 10x42 SE has an apparent field of view of 60 degrees. The 8x42 LX has an AFOV of 56 degrees. I like a wider AFOV and the 10x42 SE has an advantage over the 8x42 LX in this category. The 10x42 LX has the same AFOV as the SE, however, so this feature isn't a deciding factor between the SE and LX lines. Further, the choice between a 7 degree true FOV with an AFOV of 56 degrees and a 6 degree true FOV with an AFOV of 60 degrees is something that needs to be decided by actually using both instruments.

Of Magnification, Exit Pupil Size, and Detecting Faint DSOs

In comparing fainter deep sky objects (DSOs) between the 10x42 SE and 8x42 LX binoculars, I received my biggest surprise of the evening. While I expected the 8x42 LX would show fainter objects due to the larger exit pupil, it did not. This supports Ed Z's finding that magnification should be weighted more heavily than exit pupil size.

The most important difference between the two instruments, optically, is the difference in magnification. 2x may not sound like a lot, but it has a dramatic effect on the view. This is not to say, that 10x is necessarily a better choice than 8x. Along with the additional magnification comes a narrower field and a less stable image. Observers who are troubled by shakiness when observing with binoculars will definitely find the 8x instrument more comfortable. For myself, I often hand hold 20x80 binoculars so I wouldn't say I'm unduly concerned with the issue. Still, I've found the 8x LX binoculars extremely pleasant to observe with and have little doubt that the lower magnification is at least partially responsible for this.

Observation Notes

What follows is a collection of notes about my impressions from observing a variety of objects with both instruments. For the most part, I have not attempted to empirically quantify the differences and am reporting impressions that are somewhat subjective. However, I believe most observers would experience similar results.

M4/M80 in Scorpius

Antares seems slightly more vivid in the 8x42s, possibly because contrast isn't quite as high. The difference is not dramatic. M4 is equally easy to observe in both instruments and appears as a bright round glow. M80 is visible in both instruments, but is easier to see as non-stellar and to separate from a nearby star in the 10x42s.

The Bug Nebula in Scorpius (NGC 6302)

You've got to be kidding me! Stephen O'Meara states that the Bug Nebula can be seen in 7x35mm binoculars but I have to confess that I had no luck observing it in either the 8x42 or 10x42 binoculars and found it fairly challenging in the 20x80s. I suppose being Stephen O'Meara and observing from Mauna Kea has its advantages...

M3 in Bootes

This bright GC appears similar in both instruments, but seems more dramatic in the 10x42s because it is both larger and more prominent in the field of view. I think part of the reason for this is that the triangular asterism that includes M3 is more prominent in the field of view.

NGC 5466 in Bootes

This faint GC is noticeably brighter in averted with the 10x42s than with the 8x42s, but can be seen in both instruments. When viewed through a telescope, it is a faint loose globular cluster that looks more like an open cluster than a globular. It's reminiscent of NGC 5053 in Coma Berenices. Considering how faint it is in telescope (even an 11-inch SCT), it's surprising that 5466 can be readily seen in 8x and 10x42mm binoculars. Part of the trick is knowing where to look. Although it's not that hard to see if you pinpoint the location, I think it would be extremely difficult to locate by sweeping across the field.

Ron had taken a break from working with his 11-inch SCT, and I asked him to view 5466 with both the SE and LX binoculars. To help him locate the object, I found it in binoculars myself and then pointed at it with a green laser pointer while keeping the object in view with my binoculars. Ron just followed the laser beam with his binoculars to locate object. As goofy as this may sound, it works extremely well with binoculars or telescopes.

Ron's impressions were nearly identical to mine. He could see the object in both the 8x and 10x42mm binoculars, but it was more apparent in the 10x SEs.

M11, M26, and NGC 6664 in Scutum

This trio of open clusters in Scutum appears in the same field in both instruments, though it's framed a bit more nicely in ample 7 degree field provided by the LX. The additional 2x magnification did not make much difference for M11, which is an extremely concentrated and bright cluster. M26 was easier to detect as non-stellar with the 10x42s than with the 8x42s. It's fainter, and has a concentrated core which makes it appear more star-like. However, it is detectable in the 8x42s without too much difficulty.

NGC 6664 is a faint cluster near Alpha Scuti frequently overlooked in favor of its splashier neighbors. It's surprisingly easy to see. When I first looked for it I was amused by how frequently I had looked at M11 without noticing this nearby cluster. It's not a small object: Robert Strong lists it at 15 minutes of arc (one minute larger than M11) in his Sky Atlas 2000 Companion. It requires averted vision (at least with 42mm binoculars). It's a tad more conspicuous with the 10x42s but easy enough in the 8x42s. It appears in averted vision as an oval glow.

The usually reliable Crossen/Tirion Binocular Astronomy states that the glare from magnitude 4.2 Alpha Scuti makes spotting NGC 6664 difficult in 7x binoculars and at least a 10x instrument is required to separate the cluster from the star. It's a good bet they weren't using 8x42 Nikon LX binoculars(!) because it is not hard at all in the LXs. The Crossen entry on 6664 goes on to state that it contains two Cepheid variables -- only eight other clusters in the galaxy are known to contain Cepheids. The distance is quoted at "well over" 10,000 light years, presumably calculated with the aid of the Cepheids. M11, by comparison is estimated at 5,500 light years, a little more than half the distance. 6664 would not rival M11 even if it were at the same distance. It's a low concentration cluster while M11 is one of the richest and most concentrated open clusters known. Another interesting point -- Strong reports the distance of NGC 6664 in his SA2K Companion at only 4,200 light years. I wonder which is accurate?

This is such a rich field of view it deserves more attention than I have given it tonight. Additional research and detailed maps would doubtless yield additional objects of interest for binocular observers.

NGC 6822 in Sagittarius (Barnard's Galaxy)

This interesting galaxy was one of the few disappointments during the observing session. I had hoped to catch a glimpse of it in the 8x LX and 10x SE binoculars but failed to do so. It was just visible in averted with my 20x80 MegaViews. NGC 6822 is an irregular dwarf galaxy, one of a number in the local group. I've read its distance reported from 1.8 to 2.8 million light years. It's the subject of an extremely fine Astronomical Photograph of the Day (APOD) from a few years back. I got a club member to image it with our 30-inch reflector and the club's Apogee CCD camera once and the image was scarcely less impressive than the APOD picture, though it was in black and white.

Paradoxically, NGC 6822 is easier to observe in smaller richest field telescopes and large binoculars than in larger telescopes. Its surface brightness is reported as 14.8 magnitude, which is a bit deceptive considering the ease with which the object can be observed using 4 or 5 inch refractors. It is listed as Caldwell 57, and though I am not a fan of the Caldwell list, I am delighted with Stephen O'Meara's The Caldwell Objects, which gives a detailed account of this galaxy. O'Meara states that the galaxy is visible in 7x35mm binoculars under the right conditions (Mauna Kea, etc. ).

Although I did not record the specific time of my attempted observation (a cardinal sin), it would have been in the neighborhood of 1:00 AM. The galaxy didn't transit the meridian on June 22, 2004 at the Land of OZ observatory until 3:00 AM so it wasn't at its highest point in the sky. I plan to keep working at seeing it with the 8x42 LXs. I wonder how many observers have detected this galaxy with small binoculars?

NGC 6709 in Aquila

Easily visible in both the LX and SE, this open cluster seemed a bit "grainier" in the 10x SE. But when I tried to count stars in both views, I couldn't really quantify the difference. I could pick out 2-3 stars with either instrument. In both instruments, considerable nebulosity from unresolved stars is present, which is why I would categorize this cluster as an extended object in 8x and 10x binoculars.

The clusters 6738, 6755, and 6756 are less frequently observed than 6709 but at least for the first two they are not hard to see in 42mm binoculars. Both are nebulous objects in instruments of this size -- I could not resolve stars in either. NGC 6756 was not visible in either the 8x LX or the 10x SE, but could be seen without trouble in the 20x80s. It's quite near 6755, and a bit less than half the size. Don't look for it in the Sky Atlas 2000 -- it's not shown. It is shown in the Herald-Bobroff (chart C43) and also in the Uranometria. The Night Sky Observer's Guide includes information about both 6755 and 6756. The pair of clusters is an enjoyable sight in larger binoculars and worth the effort to locate.

Dark Nebulae in Aquila and Ophiuchus

I haven't concentrated much on dark nebulae to date, though they are both plentiful and interesting enough. Just from casually glassing about, I've noticed a profusion of these objects in eastern Ophiuchus ( a bit west of the M24 Star Cloud in Sagittarius) and also on the western side of Aquila from west of Altair and southward. I spent ten minutes or so wandering about in these fields with both the LX and the SE.

Not surprisingly, the LX with its lower magnification, steadier view, and wider field has a clear advantage for this sort of wandering about. Many of the dark nebulae are sprawling objects which appear to best advantage in a sharp 8x glass. That's not to say the 10x SE is unsuitable for this type of observation. And in some cases, typically for smaller dark nebulae with intricate detail, it provides the better view.

Sagitta, Vulpecula, Delphinus, etc.

One doesn't normally think of constellations as being binocular objects but they are delightful to observe in binoculars and from urban locations binoculars are often the best way to see them. It's a surprising fact that more stars can be seen from an urban backyard with binoculars than can be seen naked-eye from the best dark sky site on the planet. On a good night, the 8x42 LXs reach down to 8.5 mag, and possibly even fainter, from my backyard in midtown Kansas City. Predictably, the 8x42 LX with its 7 degree field of view is the champ in this category. It shows more of each constellation and shows it more steadily.

Alberio in Cygnus

The 10x42s have a clear advantage when observing this double. It is cleanly split and the individual colors of the two stars are distinct. It is harder to split in the 8x42s and the individual colors are not apparent. In fact, the 2x advantage is more critical for observing closer doubles (binocular doubles) than in locating faint objects.

Conclusions

After comparing views between these two instruments for several hours, what conclusions have I reached? The first thing I would say is that the Nikon 10x42mm SE binocular is an outstanding instrument for astronomy and belongs on the short list of any observer seeking top performance in a handheld instrument. However, I had little trouble choosing the LX over the SE and would not hesitate to do so again.

Ergonomically, the choice is easy. The LX is significantly more comfortable for me. The combination of twist-up eyecups, locking diopter adjustment, and overall fit and feel are substantial advantages. Although the LX may have a slight edge in overall sharpness, the performance is close enough that I would have difficulty choosing between the two based on optics alone. After making this long series of side by side comparisons, though, I am skeptical of reviews claiming the SE outperforms the LX optically. Side by side comparisons between the 10x LX and 10x SE should be of interest in this regard.

Choosing between an 8x42 or 10x42 LX is a more difficult decision than choosing between the LX and the SE. Fainter objects are easier to detect with the 10x instrument. And for those who frequently observe from urban or suburban locations, the 10x instrument may be the better choice on this head alone. However, I did not find a single instance of an object observable in the 10x that could not also be seen in the 8x. The difference in performance on faint objects, while noticeable, was not dramatic. I hope to do some additional testing under light polluted skies to compare the instruments in this regard. As demonstrated with the notable example of Alberio, closer binocular doubles are where the benefits of 10x over 8x seem most apparent.

Had I realized when purchasing the binoculars that 8x42s would not show fainter objects (a misapprehension this observing project cleared up for me), I probably would have chosen the 10x42 LXs instead of 8x. But now that I own the 8x binoculars I can't say I regret the decision. The wider and steadier fields make it a pleasure to observe with, and if I want more magnification I own a fine pair of 20x80 binoculars. And, of course, there's always the option of adding another binocular to my collection . . . "But honey, I need additional magnification to separate double stars."

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