Some Comments on Pocket Binoculars.

A representative sample of pocket binoculars; clockwise from the top: the Opticron Aspeheric 8 x 25 LE, the Pentax DCF 9 x 28 and the Celestron Nature DX 8x 25.

Hello again everyone!

Binoculars come in all shapes and sizes, and at prices that suit virtually everyone’s budget. As you may be aware of, I’ve re-ignited my interest in the modern binocular market, having somewhat neglected it for the best part of three decades. But I’ve been making rapid progress and would now like to discuss the market for the smallest binoculars; the so-called pocket variety.

Though any objective look at this market is very much like hitting a moving target, I acquired three products which I believe are fairly representative of the entry-level to upper-mid to premium class of pocket binocular that can be purchased. First off, let’s come up with a working definition of a pocket binocular. To my mind, these would be instruments under 30mm in aperture and have magnifications in the range from about 6x  to 10x. As their name suggests, they are small enough and light enough to fit inside a regular pocket (though some pockets are certainly larger than others lol!)  and so would be no larger than about 4 square inches in area and weigh less than about 400g.

Unlike all the other classes of binocular; including compacts, full-size and large instruments; the reader may be surprised to learn that even the most expensive models in the pocket class of binocular are not exorbitantly priced. Indeed, you can acquire models from the threee premium binocular manufacturers(Zeiss, Swarovski and Leica) for about £500 or sometimes less. This reflects their limited utility; very useful for hiking and other outdoor excursions that require strict minimisation of weight but ultimately not an instrument one would happily use where there is easy access to a larger(say mid-size) instrument. That said, you can get essentially the same performance out of some models that cost significantly less than the premium brands, if you know what to shop for. That just reflects how manufacturing technology has caught on.

Now, I do a fair amount of hill walking and have learned the hard way that even my favourite binocular – the magnificent Barr & Stroud Savannah 8 x 42 wide angle – is a bit of a pig (weight wise) to climb with. That stoked my interest in acquiring a smaller unit dedicated to enjoying quick looks around the landscape from an elevated vantage and this naturally led me to testing three roof prism-based units units that can be acquired relatively inexpensively; either newly purchased or acquired second hand; the Celestron Nature DX 8 x 25mm (purchased new for £59 plus shipping), the Opticron Aspheric 8 x 25mm LE (actually my wife’s binocular, purchased new for £110 a few years back with the slightly modified new version retailing now for £129) and a Pentax DCF 9 x 28mm (purchased second hand for £119 but still under warranty and now available for £199 in the newer (AD) incarnation).

Yours truly recently surveying the landscape with a pocket binocular atop the Meikle Bin, Campsie Fells, Scotland, elevation 1,870 feet. Check out the gibbous Moon at upper right!

These were not acquired for specific astronomical use, though I did find out that there are significant differences between them when looking at some astronomical targets. But you’ll need to read the rest of this blog to find out those details!

Nota bene: A new discussion has arose on tiny binos here lol.

Let’s take a closer look at the instruments. First up, the Celestron Nature DX 8 x 25. Full specifications here.

The Celestron Nature DX 8 x 25 has twist-up eyecups giving very comfortable eye relief.

This very cost-effective pocket binocular from Celestron offers many attractive features for the savvy consumer. Weighing 343g, the package includes the binocular, a basic neck strap, a lens cloth, nicely fitting rubberised ocular and objective lens covers and a decent carry case. It also includes a basic instruction manual to get you going fast. What is rather remarkable is that the binocular has a few optical features that were offered only on premium models just a decade ago; including fully multi-coated optics, BAK-4 prisms, with phase correction. It is also waterproof and is purged with dry nitrogen gas preventing internal fogging and minimising internal corrosion. The Celestron Nature DX 8 x 25 offers a very generous field of view of 7.2 angular degrees which is actually quite remarkable for such a low cost unit.

Looking down on the Celestron Nature DX 8 x 25. Note the specifications on the large, central focusing wheel.

The plastic eyecups twist upwards giving a comfortable 14mm of eye relief. The cups are kept down for eye glass wearers. The dioptre setting is reassuringly stiff and is located just under the right eyecup. Viewing through the binocular is very comfortable and the large field of view is bright and sharp across most of the field. Only in the outer ten per cent of the field can one detect a little softening of the image. Chromatic correction is very good, as is the control of pincushion distortion.

The objective lenses on the small objectives of the Nature DX binocular have good coatings.

It has a stiff, central hinge that can accommodate virtually all IPDs. It has quite a solid feel in use. The body is made of a low mass but strong polycarbonate material with a plastic- like(read non rubberised) green overcoat. Grip is adequate but I would have liked to have a higher friction, rubberised over coat.

The large, centrally placed focusing wheel is quite stiff and only turns through ~ 290 degrees, so less than 1 revolution between infinity and closest focus(an impressive 2m). This result is at odds with the claims of some other reviews I have read on the Nature DX (720 degrees, or two full revolutions claimed!). See here for an example. Perhaps it is unique to this small Nature DX model?

The instrument gives remarkable depth of focus! When the wheel is turned to the end of its travel so that objects in the far distance are focused, my eyes were able to get very sharply focused images all the way down to about 35 yards distance!

I did discover a significant flaw in this instrument however; point it at a bright light source at night or at the Moon, and it will show strong internal reflections/lens flaring. I found observing the Moon to be particularly annoying with this binocular and if imaging a backlit scene during the day, it will also throw up the same reflections which reduces the punch of the image. You cannot see these reflections when looking at most scenes though; it shows none on even the brightest stars, as verified by my testing on the Dog Star, Sirius. I do not know whether these internal reflections are found on other Nature DX models but it can (and should) easily be tested. But for £59 plus shipping, I can’t really complain. Afterall, some internal reflections are found in all binoculars, even premium models.

The Celestron Nature DX pocket binocular comes with a decent soft-padded case, a lens cloth and a basic neck strap. The ocular and objective lenses also have good rubber caps.

The user will have to decide if this flaw is annoying enough to justify passing on the purchase of this product. Everyone’s different I suppose! This might bother some observers more than others; the instrument is otherwise quite excellent and I can see how it has been lauded(Cornell Ornithology Lab) as a great entry-level birding binocular. That said, all of the reviews I have read never mentioned this flaring/internal reflection, which is somewhat alarming. It just seems to have gone unnoticed. I think simple tests like this should be mandatory for all optical testers.

The model has recently been discontinued from the Nature DX line.

Next up, the Opticron Aspheric 8 x 25 LE

The little 8 x 25 Opticron Aspheric LE pocket binocular.

The Opticron Aspheric LE 8 x 25 is a well-designed pocket binocular. Tipping the scales at just 291g, this is the lightest binocular of the three by a significant margin. It has a very well constructed double-hinge design that also allows the barrels to be folded right up to each other, also making it the most compact of the three models discussed here. The hinges fold outwards to accommodate virtually any IPD and can be comfortably set in seconds.

The Opticron Aspheric LE 8 x 25 has an elegant double-hinge design that enables it to be folded up( it’s just 66mm wide) for very snug transport anwhere, anytime.

Unlike the Nature DX, it is not weatherproof or nitrogen purged; but not a big deal as my wife likes to remind me. As you can discern from the first photo of the unit above, the optics are of high quality with a full multicoating, which includes a phase correction coating on the roof prisms, that delivers bright, high-constrast images of objects during well-illuminated, daylight conditions.

The eyecups twist up for non-eyeglass wearers and offers generous eye releif (16mm). The eye cups are of a higher standard than those found on the Celestron Nature DX and appear to be rubber-over-metal. They stay in place reasonably well.

The rubber-over-metal twist up cups are of a higher standard of workmanship compared to the Nature DX binocular and offer 16mm of eye relief. Note the small, central focusing wheel that is quite hard to grip.

Optically, this is a sharp shooter, offering well-correcetd images over a 5.2 degree field. I felt that this was rather a small field though, in comparison with that offered by the Nature DX binocular discussed previously and does take a bit of getting used to if one is especially fond of wider views. But its aspherical optics certainly deliver the readies, producing a lovely, flat, low-disortion images from edge to edge. I guess this is the price one has to pay for a more restricted field of view.

Internal reflections are much better controlled in this unit than in the Nature DX, as evidenced by pointing the instrument at the bright Moon at night or other bright sources of artificial light. Backlit scenes during the day are a tad more contrasted too. Besides the small field, the only other issues I had with the Opticron pertain to its very small focusing wheel, which is hard to grip in my (not overly large) man-sized hands, and it’s a nightmare to use with gloves.  It can often prove difficult to turn the focuser fast enough to keep up with moving terrestrial targets such as rapidly moving corbies. I believe the updated WP model(with the same specifications so far as I can see) has a slightly larger focusing wheel with better grip.

In addition, I found its very light weight a bit offputting, as it was difficult to find a good, secure position in my hands. The unit comes with its built-in lilac coloured lanyard, so no need to affix a separate strap. I’m not really a fan though, as it feels as though you are being slowly garrotted when walking with the binocular around your neck lol!

The tiny but well made carrying pouch for the Opticron Aspheric LE 8 x 25 pocket binocular.

All that being said, my wife loves it; lanyard and all! She says it looks as good as operates, with small, elegant black tubes that easily fold up in tiny pockets. It’s also perfect for her quick looks at the bird table in our garden and for taking on her hill walks with her girlfriends. I don’t use it very often though, as her dioptre setting is much different to my own!

Finally, let’s take a good look at the Pentax DCF 9 x 28mm LV pocket binocular.

A liitle gem: the remarkable Pentax DCF 9 x 28mm LV pocket binocular.

 

Some information about the unit when the product was first launced back in 2009.

And here’s an independent review of the same instrument.

The reader will note something rather interesting from the review article linked to above; all of the compact binoculars highlighted in the table the reviewer presents, including premium models, like the Leica Trinovid 10 x 25, do not use ED glass. This is an important point, as it serves to highlight the fact that no real gains in performance are achieved by inserting one or more ED elements in the objectives of these binoculars. If there was an obvous advantage, don’t you think companies like Leica would have insisted on using it? Though it is conceded that some pocket models like the Zeiss Terra ED 8 x 25 do have ED elements, their cost is actually consideraby less than the Leica Trinovid(as of early 2019 average UK pricing). I view the use of ED glass in such small binoculars as a clever marketing ploy.

Now back to the Pentax DCF binocular.

The instrument tips the scale at 365g; definitely on the heavy side as pocket binoculars come, but still under the 400g cut-off point between pocket and compact models.

The instrument is weather proof and is dry nitrogen purged to prevent internal fogging of the elements. The optics are fully multi-coated and the prisms have been phase coated to improve brightness and contrast in the images. The instrument has a field of view of 5.6 degrees, noticeably larger than the Opticron Aspheric but not nearly as large as that yielded by the Nature DX. Then again, the Pentax provides a power of 9x and not 8x as the other models do, which invariably has an impact on the maximum true field achieved.

Looking from the ocular end of the Pentax DCF 9 x 28.

The instrument is very well endowed from a mechanical point of view, with a large centrally placed focusing wheel with excellent grip, even while using gloves. The wheel rotates through about 300 degrees, so not very much in the way of travel  from infinity to minimum close focus. The barrels are covered with a tough rubber coat making it especially suitable for rough field use.

I really like the metal-over rubber eyecups, which are strong and comfortable. The user has a choice of 4 positions, from fully down use with eye glasses to fully extended. I found having the eyecups twisted up to the mid-position provides all the eye relief I require without glasses. When clicked into place at a given position, the eyecups maintain their positioning even after applying unreasonable pressure.

The high quality twist up rubber over metal eyecups click into four positions and hold those positions well in field use. Note the dioptre ring under the right eyecup.

The underside of the binocular has thumb indentations to assist holding the binocular steady in field use.

The underside of the binocular has thumb indentations to assist with holding the binocular stably.

The anti-reflection coatings on the Pentax DCF are very well applied and I would rate them superior to those on the Opticron Aspheric model previously discussed. The Pentax is not nearly as compact as the Opticron however, as seen in the photo below. This was not found to be a problem; it’s still small enough to fit into a coat pocket or the palm of my hand.

The central bridge connecting the barrels do not allow the Pentax DCF to fold into the same compact size of the Opticron Aspheric binocular.Note the coatings on the Pentax( left) are a little bit less reflective than the Opticron( right).

The central hinge of the Pentax DCF is reasonably stiff but not quite as stiff as that of the Nature DX model. I find that the latter is just right for quick deployment with the correct IPD(for my eyes) achieved in seconds from its fully folded in position.

The objectives of the Pentax DCF LV are noticeably larger than the 25mm models, which has an immediate impact on its light gathering performance. Afterall, it gathers about 25 per cent more light than the other models discussed in this blog. I like the recessed position of the objectives with a little overhang from the barrels. This helps to reduce lens flaring and /or the control of stray, off-axis light while using it in the field.

The Pentax DCF objectives have excellent coatings applied to them and are nicely recsessed from the top of the barrel to help suppress stray, off-axis light.

The Pentax DCF LV 9 x 28 feels very comfortable while in use and has more of the attitude of a 30mm compact binocular than the smaller 25mm instruments tested previously. The 9x magnification is immediately apparent compared to using a 8x unit.The human eye will easily register a 12 per cent increase in magnification with just a little experience. Images appear equally bright in the Pentax in comparison to the Opticron (afterall they have the same exit pupil of 3.1) but the greater field of view is readily appreciated. Images are very sharp and contrasty with only very slight softening at the edge of the field. Control of stray light is very good; almost as good in fact as my larger Barr & Stroud roof prism binoculars( yep, you really have to experience them to know of course!). This is immediately apparent when turning the instrument on a bright Moon which shows that glare and internal reflections are very well controlled. The large focusing wheel is a bonus, moving smoothly and precisely but with a little bit more tension than I would have liked. Still, it’s perfectly fine for the tasks I intend to use it for.

I measured the close focus to be just under 10 feet. I find the 9x very useful in daytime use as it brings objects that little bit closer, aiding in the identification of small birds or subtle landmarks in the distance. I’m glad I didn’t go for something with a 10x magnification though, as this would probably have generated images a tad too dim for my liking, but your mileage may vary! It will serve me well for occasional hill walking ventures and at sports events, where its small size won’t cause me to look too out of place.

If money is an objection or if you’re frugal like me, I’d recommend purchasing quality instruments second hand. A few thoughtfully chosen questions and the answers they generate from the seller never go amiss. If you do your research and know what to look for in a binocular, you can secure real bargains for relatively small financial outlays.

Ultimately though, I would not recommend spending huge amounts on these small instruments. I find them, well, a bit unexciting. They’re just too small to use for prolonged astronomical appllications and their daytime performance, while good in bright light conditions, is noticeably inferior to mid-sized instruments under dull or low light situations, such as at dawn or dusk. In comparison, my 8 x 42 is, by far, my most used binocular; providing a great balance between portability and utility by day or by night. Sure, it’s nice to have a quality pocket binocular around, but unless I were to embark on a trek through the Himalayas, I can’t see myself reaching for one all that often.

Thanks for reading!

 

Dr. Neil English’s latest historical work, Chronicling the Golden Age of Astronomy, takes a detailed look at the life and works of great telescopists from the early 17th century right up until the modern era.

 

 

 

 

De Fideli.

13 thoughts on “Some Comments on Pocket Binoculars.

  1. Another interesting point about using compact binoculars, is because their smaller objectives deliver a smaller exit pupil. This means that if you have any astigmatism in your eyes, the smaller exit pupil occupies less area of your eye, giving a sharper view.

  2. Hello Douglas,

    Yes indeed. A very good point; smaller exit pupils allows one to form images from the sharpest part of the eye.

    Regards,

    Neil.

  3. I accidentally came across this phenomenon one day observing the sun with the two scopes i had at the time. One was a skywatcher 102 f/9.8 acro, the other was C8. No matter what i tried, i could not get as sharp a view in th C8 as i was getting from the smaller acromat. It soon dawned on me that at low powers the acro had a much smaller exit pupil, giving the sharpest view. Increasing the magnification in the C8 ( thus reducing the size of the exit pupil) sharpened its view considerably, revealing excellent details of sun spots. Is it now any wonder that I have taken to binoviewing. As it turned out, my left eye ( not my primary observing eye) had much better visual acuity (lower astigmatism).

  4. Hello again Douglas,

    That’s an interesting story. Thanks for sharing. I can definitely relate to that. My Pentax PCF 20 x 60 gives incredibly sharp views from edge to edge during daylight observing. And it’s no doubt due to the small (3mm) exit pupil and the aspherical eyepiece optics. I am also in the process of making a change to binoviewing as I have been so very impressed with the power of two eyes using my binoculars. Need to save the pennies though in the meantime.

    Regards,

    Neil.

  5. I noticed that you have taken to newtonian scopes. Having owned a few and binoviewing with them, a barlow or OCS will be required to reach focus. I found the best results for higher powers came from using the lens from my GSO two inch ED barlow screwed into the 2inch to 1.25 eyepiece adaptor, and mounting the bino into that. This combination allowed focus with room to spare, and a power increase of 2.6x.

  6. Hi Doug,

    Yes sir, Newtonians are my favourites. Best bang for the buck by a country mile and never been happier since I got away from refractors( I spent far too much on them in the past).
    I’m actually enjoying a great evening of double star observing with my little 130mm F/5 Newtonian here at the moment!
    Thanks for the advice regarding binoviewers and Newtonian optics. I’m half inclined to consider the Orion Premium Linear Binoviewer, which I’ve heard good things about, especially in regard to not needing an OCS and Barlow lens. The only issue is the restricted clear aperture of 17.1mm on the unit which will restrict the field while using my lowest power 1.25″ oculars, but at least it will give the same image scale as the native eyepiece used in monocular mode. Fairly pricey though: ~ 380-£400 UK, so not cheap!

    Away out again!

    Regards,

    Neil.

  7. Even if you used a standard binoviewer with a 2x OCS, the focal length of your 8 inch f/6 would end up at 2400mm. With a 24 mm eyepieces, that would give you 100x. For me, i am using more than 100x for Luna planetary, so not a problem. I tend to go mono for double stars and deep sky. The binoviewers you are interested in don’t get a lot of good reviews on Cloudynights. Seems going down to 17.5 aperture at eyepiece end of bino is self defeating, because you loose the benefits of longer focal length eyepieces. A U.S firm called Siebert Optics make a range of OCSs that can get you down to 1.25x and lower with guaranteed focus. I recently bought a GSO 8 inch classical cassegrain to have that refractor observing position with reflector performance on a eq mount. Waiting for the clouds to go away and try it on the moon and Jupiter. What i have seen so far is promising. Clean intense diffraction patterns on doubles, and the pup, easy.
    .

  8. Good morning Doug,

    You obviously have much more experience than I have with binoviewers. My knowledge is very limited concerning these devices, but I’m not in any hurry to committ to a single line of action. I don’t want to spend good money on something I’ll regret acquiring down the line, so any advice concerning these devices is very welcome indeed.
    I was basing my comments on the Orion model on a review written by William Harwood in the March 2019 issue of “Astronomy Now” magazine. He seemed to love the device and stated that he got the best view of the Orion Nebula he has ever experienced using it with his 16″ f/4.5 Discovery Dob. That said I was very surprised that he never gave as much as a mention to the restricted clear aperture that I picked up in reading the specifications of the device. He stated that he used 20mm Televue Plossls and a pair of 23mm budget oculars marketed by Stellarvue. I have learned long ago to take some magazine reviews of equipment with a large pinch of salt!

    What model of binoviewer would you recommend using f/5 Newtonian optics and what is the lowest power/widest field I could realistically achieve using it?

    Ps. With a name like yours I was thinking you were based nearby. But your comments on bagging “the Pup” makes me think you’re not ‘local.’ Somewhere a lot further south perhaps?

    Regards,

    Neil.

  9. Yes, way further south, Australia. Might be a good idea to borrow a binoviewer if you can.

  10. I think I’ll give the Orion viewer a go; it’s simple and hassle free. No screwing Barlows and OCSs in the dark etc and I’m rather intrigued by Harwood’s comments. I don’t think he meant to mislead anyone. It will have to wait a while though; the autumn methinks!

    Neil.

  11. Welcome to the land of brain summation. What the grey matter can do with two eyes over one eye may surprise you.

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