A work begun July 1 2020

Preamble:

** New  Review 5 added below, as well as an expanded conclusion towards the end of the blog.

  Review 1

  Review 2

  Review 3

  Review 4

** Review 5

Specification: 8 x 42

Eye Relief: 17.2mm

Field of View: 8.1 angular degrees (142m@1000m)/

Measured at 8.0 degrees in field tests

ED glass: Yes

Body: High density Polycarbonate, textured rubberised overcoat.

Weight: 692g

Coatings: Fully Multi-Coated

Dielectric Phase Coating: Yes

Dimensions: 12cm x 12cm x 4.5cm

Nitrogen Purged: Yes

Waterproof: Yes (1.5m for 3 min)

Tripod Mountable: Yes

Accessories: Padded soft case, high quality lanyard, instruction sheet

Warranty: 10 years

Retail Price: £205 UK

 

The British optics firm, Charles Frank of Glasgow, has been selling and repairing optical instruments for nearly three and a half decades. In 2016, the firm moved south to Halesworth, Suffolk, where they changed their name to Viking Optical. Recently, the company launched an exciting range of affordable roof prism binoculars featuring a number of impressive optical features exhibited in their Kestrel, Merlin and Peregrine(all keen eyed raptors) binoculars. Three models are offered in 8 x 32, 8 x 42 and 10 x 42 configurations, and all feature fully multi-coated optics, dielectrically coated and phase corrected BAK 4 prisms and objectives containing ED glass elements in a fully waterproof housing. Although all these models are assembled in China, I reasoned that their acquired knowledge in repairing binoculars over many years would put them in a strong position to offer a quality experience, so I pulled the plug and decided to order up the 8 x 42 Kestrel model for optical testing and evaluation.

First Impressions

The binocular was ordered up from Amazon and the instrument arrived in the evening of the following day. I was immediately impressed with the packaging of the Kestrel. Instead of the regular colour-saturated cardboard box that usually attends many of the binoculars that have passed through these parts, I received a very fetching presentation box with the phrase “Extend Your Horizons” printed on top. After removing an outer slip case, the binocular and accessories were carefully packaged away inside.

The package contained the binocular inside its soft padded case, a high quality padded neck strap and one page instruction sheet with details of the warranty. The company states that the binocular went through several stages of testing before the instrument was finally packaged up for distribution. Both the ocular and objective lenses came with standard soft rubber caps which can be permanently affixed to the binocular. I was half expecting a lens cleaning cloth but none was provided.

The binocular has a very attractive appearance, with the optics housed inside a strong polycarbonate body overlaid by an anthracite-coloured, texturised rubber armouring. While I have used binoculars with magnesium alloy bodies before, I have not noticed any particular advantage of using metal bodies over their synthetic polymer counterparts, except perhaps to shave off some excess weight. But at 692g, this binocular is not exactly heavy. Indeed, surveying the market in 8 x 42 roof prism binoculars quickly reveals that the weight of the Kestrel falls into the median in the range for instruments of this specification.

The fetching anthracite colour of the binocular is beautifully complemented by the sky blue logo of the company and its ED billing inlaid on the top surface of the instrument. I’m not normally taken much aback by the cosmetic appearance of a binocular but I must admit to really liking the colour scheme of this instrument!

The binocular has a single centrally placed hinge that is reassuringly rigid. Once adjusted to get your particular interpupillary distance (IPD) right, it stays in place even when taken out of and placed back inside of its padded case.  Both the focus wheel and right eye dioptre are constructed from metal and coarsely stippled for maximum grip. The twist-up eye cups are of very high quality, rubber over metal that offer 3 positions. With a very generous eye relief of 17.5mm(measured), they afford very comfortable viewing for those who wear eye glasses and those who don’t. Most importantly, when clicked into place they hold their position very solidly, even after an undue amount of pressure is applied.

The underside of the body has two small thumb rests which allow your fingers to naturally gravitate towards when handling in the field. Overall, I found the Kestrel to be very ergonomically designed.

The focus wheel moves with what I would describe as slow-to-standard progression. There is a little bit of play in it which can sometimes result in over- or under- focusing, especially when imaging a fast moving object, but overall I felt it was perfectly adequate for most purposes one would use a binocular like this for. The wheel moves through 1.5 revolutions from its close focus to beyond infinity. Having a little extra focus travel beyond the infinity setting may not have any immediate advantages, but I’ve found that it is quite important when attempting to clean up the image at the periphery of the field. In other words, having a slightly longer focus travel can help alleviate some of the off-axis Seidel aberrations found on most any binocular image.

The objective lenses on the Kestrel have very nice and evenly applied anti-reflection coatings.

What’s more, they are very deeply recessed – exceptionally so, I’d say. I measured them at a whopping 10mm – significantly deeper than any other binocular I have encountered. This affords exceptional protection against rain, and wind-borne dust and will also attenuate the build up of contrast-robbing dew.

All in all, I was well pleased with the ergonomics and physical presentation of the Kestrel, but all of that counts for nought if the optics are not up to scratch.

Mounting the binocular on a tripod is easy to do by unscrewing the stalk at the front end of the bridge, between the two barrels,and which enabled me to test the collimation of the instrument by observing well defined targets on a hillside a few miles distant, looking for both horizontal and vertical asymmetries in the images presented in both optical tube assemblies. To my relief, the Kestrel showed no misalignment issues.

Stray light tests

No roof prism binocular, no matter how well made, can perfectly stave off unwanted reflections, diffraction artifacts and diffused light when a very strong light source is directed inside the instrument Setting up my standard iphone torch light test, I was very impressed with the results I obtained with the Kestrel. I used two controls to compare the views with this instrument; my trusty Barr & Stroud Savannah(which exhibits excellent stray light control and very subdued diffraction spikes) and my superlative Leica Trinovid BCA 8 x 20 pocket glass, which, until now, offered the best results I have recorded in such tests.  Well, the Kestrel served up an exceptionally clean image, with very low unwanted reflections and an almost imperceptible diffraction spike. The result bested the Barr & Stroud binocular and was the equal of the Leica but with a far less obvious diffraction spike! Furthermore, just like my two binocular controls, diffused light was pretty much non existent.

Further testing on a sodium street light confirmed the same results; the view through the Kestrel had well nigh perfect results with no annoying internal reflections, zero diffused light and no diffraction spikes! I did however detect rather strong off-axis flaring with the Kestrel, which was more pronounced than in the control binoculars, as evidenced by placing the street light just outside the field stop of the instrument.

Overall, I was very pleased with the outcome of these stray light tests, which suggested that the Kestrel would likely deliver exceptionally punchy images, rich in contrast during normal daylight use.

Daytime testing

My first day of testing took place on an overcast June day. Examining some tree trunks a few tens of yards distant showed a very wide and wonderfully sharp and vibrant image. Compared with my Barr & Stroud Savannah 8 x 42, the colour tone was noticeably more neutral in the Kestrel compared with the very warm yellowish tones in the former. Within its large sweet spot, I judged the image sharpness to be a tad better in the Kestrel than in the Barr & Stroud. Examining the summit of a nearby hill against a bright overcast sky also revealed that the Kestrel was better corrected for chromatic aberration as judged by the absence of a very faint sliver of blue fringing at the boundary between the summit and the background sky. The achromatic Barr & Stroud did show that fringe in the same test.

That said, it soon became clear to me that the Kestrel was showing some lens flare in a portion of the image similar to what I had previously detected in my sodium street lamp test, reducing its contrast in comparison to my control binocular. This flaring could be removed by simply placing my hand over the objectives, blocking off some of the bright light from the sky above it. The flaring was also reduced by observing through an open or closed window under a roof but always reappeared once I re-emerged into the out of doors.

The flaring was only slight though and I suspect that most folk wouldn’t have even noticed it, but once you see it it’s very hard to ignore it, especially since the less expensive Barr & Stroud Savannah did not exhibit such behaviour. Examining the exit pupils showed up a significant amount of light leakage which you can see in the image below:

I decided that I would contact Viking Optical describing the problem I had encountered to see if they were willing to have a technician look at the binocular. So, I fired off an email to them, describing the problem as best I could, and within a few minutes they got back to me asking if I’d be willing to send them the instrument so that they could properly assess its performance. I agreed, so back went the binocular into its case and box for shipping down to Suffolk.

I will continue this review as soon as I receive word on its progress.

A Change of Heart

I spent the afternoon of July 2 2020 comparing and contrasting the views through my Leica Trinovid 8 x 20 with the Kestrel 8 x 42 as well as the Barr & Stroud in bright sunny conditions. I detected the same weak veiling glare in the Leica and the Barr & Stroud  as I did in the Kestrel. Indeed, truth be told, it was more severe in the Leica than in the Kestrel on the same test objects, which I think is caused by its complete lack of any recession of its objective lenses. It was however a little less intense on the Barr & Stroud, but in every case it could be eliminated by shading the objectives with my hand. So I reached the conclusion that it is I who was really at fault. I have come to expect too much and have learned to spot tiny imperfections in optical performance. Furthermore, those light leaks around the Kestrel exit pupil lie outside of where my eyes intercept the image, and so will have little or no effect on the performance of the binocular.

Absolute perfection just cannot be obtained no matter how well made the binocular is. I therefore decided not to bother Viking with my petty complaint and will email them tomorrow morning informing them that I do not wish to pursue this matter, as well as to congratulate them on designing an excellent glass at such a good retail price.

Methinks a large slice of humble pie for tea is in order!

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An Aside: Veiling glare reported in the Leica Trinovid 8 x 20 binocular

A very bad case of glare in a Swarovski CL Companion 10 x 30

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Tests on Light Transmission

As I described in numerous previous blogs, the Barr & Stroud Savannah 8 x 42 is an excellent wide angle binocular, especially for its very modest retail price(£120UK), but I understand that it does not have the brightest dielectric coatings on the roof prisms( they may be either silver or aluminium). I therefore expected the Kestrel to deliver brighter images in low light conditions. So I ventured out at dusk on the overcast evening of July 1st 2020 and began comparing the views in both the Kestrel and the Savannah. Starting at about 10.15pm local time and ending at 10:40pm, I conducted simple A/B tests on some tree branches about 40 yards distant,  evaluating the brightness of the image in the binoculars as the light slowly drained from the landscape. These tests did show that the Kestrel served up the brighter images, as I would expect if they had better coatings, but the difference wasn’t exactly night and day. It was only a little bit brighter at best, becoming most apparent toward the end of the testing than at the beginning.

Investigating Claims that ED Glass Produces Brighter Images

I was also able to conduct more tests to ascertain if the presence of ED glass produces brighter images than an instrument with no ED glass. To make the test as fair as possible, I needed a binocular with good dielectric coatings but without ED glass. So, I borrowed my son’s Celestron Trailseeker 8 x 32 which I reviewed in an earlier blog. This binocular does have those all important dielectric coatings on the roof prisms and is also fully multi-coated like the Kestrel ED binocular. Because the apertures are different, I made an aperture stop of 32mm diameter from cardboard and placed it over one of the 42mm objectives on the Kestrel as shown below:

I tested the images served up with the stopped-down objective on the Kestrel, comparing them with those garnered by the full-aperture Celestron Trailseeker 8 x 32, using the same eye to examine both. Again I performed these tests at dusk, when the test tree branches some 40 yard distant were in deep twilight. The results were quite revealing! Conducting the same A/B testing as before, I concluded that there was very little difference in their perceived brightness. I did however give the nod to the Kestrel though, but only just!

This is the second test of this nature that I have conducted, with both results seeming to indicate that ED glass either does not confer brighter images, or, if it does, it’s marginal at best.

This is at odds with bold claims made by many sources in the online literature and is widely adopted as a marketing stratagem to sell binoculars to the public.

Like I stated before, it’s not so much the ED elements as much as the coatings that distinguish an average binocular from a great one!

Further Notes on Glare, its Causes & its Management

Our long summer days here in Scotland are a godsend, not only because they allow one to observe for longer durations in warm or mild weather but, as I’ve been discovering, they afford many opportunities to conduct experiments with my binoculars. Today proved to be a good day to get to grips with the glare I’ve been observing with my instruments. The afternoon was very bright and sunny but as the afternoon gave way to evening, the skies became very overcast again, so I was able to test out two very different binoculars – the Leica Trinovid and the Viking Kestrel – in these very different conditions. I now believe I have a better understanding of what causes glare in these glasses, and so, by extension, in all binoculars.

The first observation I have made is that glare is actually a lot less problematic during sunny spells than it is during overcast spells. When the Sun is shining in a sky with little cloud cover, the main light source i.e.the Sun, is concentrated in one direction and so long as you are not looking at something very near the Sun, relatively little or no glare is noticed. For example, when glassing tree trunks located at the edge of a strongly shaded copse, with the afternoon Sun illuminating it from the side, glare is very well subdued in both binoculars. This kind of glare manifests itself as a localised crescent or arc at the bottom of the binocular image with much of the rest of the field being largely unaffected. The worst culprit is the little Leica Trinovid, as its objectives have no protection from stray ambient light. The Kestrel does significantly better under the same conditions because its objective lenses are located at the bottom of a 10mm deep ‘well’ which acts as a very effective lens hood, a trick long known to photographers.

But under overcast skies, where strong summer sunlight is diffused by extensive cloud cover, glare becomes much more of a problem in both instruments and seems to be more spread out in the binocular image. Glassing the same tree trunks at the edge of a shaded copse produces noticeably lower contrast images than under sunnier conditions; even when glassing near the Sun. The reason for this must be due to the fact that in the open air, under overcast conditions, with a bright sky overhead, there are many more locations where the light can reflect off the spacers between the objective lens elements at the bottom of the binocular objective, which in turn causes this flaring to spread out or diffuse across the binocular image, reducing contrast in a more noticeable way. This is referred to as veiling glare. So overcast skies appear to produce greater damage to the image because it has a greater potential to affect the entire field than much more localised crescent glare observed in clear sunny conditions. What is more, bigger glasses, which collect more light will show this type of glare well into twilight, whereas in smaller glasses which can’t collect as much light, the same glare can’t be seen!

Consulting a birding forum, I was able to verify this and I also learned that even alpha binoculars suffer from this problem. The poor chap was complaining about glare on his maiden voyage with his fancy new Zeiss Victory FL 8 x 42 and more knowledgeable glassers were able to chime in and offer some detailed explanations and a hefty dose of sympathy for good measure!

Three points to summarise all of this:

1. The worst effects of glare can be removed by simply shielding the binocular objectives from the offending light source using your hand.
2. Glare is a fact of life for most any glass, from the most humble to the most advanced. It’s par for the course and we must accept it and move on!
3. Glassing under the canopy of a forest or in an observing booth with a roof over your head, or even donning a broad-rimmed hat will all but eliminate the worst effects of glare.

Further Notes on using the Viking Kestrel in the Field

Saturday July 3 2020

After a day of heavy rain, the clouds cleared off in the evening, leaving a tranquil blue sky. It was the perfect opportunity to go for a long walk around the picturesque Culcreuch Castle Estate with the Viking Kestrel 8 x 42. The instrument feels very solid in my hands and its fine mechanics work flawlessly. The quality padded neck strap with the company’s fetching colour logo proved very comfortable to use.  I stopped to say hello to a pair of Mute Swans and their family of five cygnets at Culcreuch Pond. The binocular served up beautiful, pin-sharp, views of the pure white plumage of the adults wonderfully contrasted with their rusty orange beaks and jet black foreheads. The cygnets had almost lost their fluffy down feathers by now and had developed their attractive tawny drapery, which stood out well against the sullen waters beneath them. And though the surface of the pond dappled in strong reflected sunlight, the binocular served up flawless images with incredible contrast and no annoying reflections.

Ambling up the path a little further, I enjoyed a fascinating fifteen minute excursion watching a group of Swallows perform their incredible feats of aeronautics (far more advanced than any human made flying machine) swooping and gliding with great speed and agility, gorging on low flying insects along a large grassy lawn immediately in front of the castle. The Kestrel proved to be a magnificent instrument to follow them, with its very large and well corrected field of view. Their prominent forked tails, iridescent blue-black upper body and almost comical, chocolate-brown faces could easily be made out as they flitted across the field of view. A lady out walking her dog, obviously curious about my glassing, stopped to tell me that a few big storms had threatened these migratory birds earlier in the year, reducing the numbers reaching our shores from Africa. It put a big smile on her face to see that it was business as usual for these noisy summer visitors!

These experiences convinced me that the Viking Kestrel 8 x 42 will make an excellent birding binocular with its superb contrast, sharpness and colour correction, not to mention its super-comfortable twist-up eye cups, generous exit pupil size and smooth focusing wheel.  As I continued to walk, I enjoyed glassing the intense colour of mature green leaves drenched with life-giving rains that made them glisten intensely in the early evening sunshine. I almost lost myself observing the intricately textured bark high up in their canopies against a gorgeous blue sky beyond. That said I must also report that there is very mild pincushion distortion at the edge of the field but certainly not enough to cause any alarm.

After sunset I ventured out again to catch a nearly full Moon skirting low in the south-southeast at about 11pm local time. To get a good unobstructed view I had to take a walk about half way up Culcreuch Castle Road. But it was worth it. The almost full Moon in all its glory hovered just above the tree line beyond a gently sloping hill, its low altitude imparting a yellowish cast to its normal pale silver countenance. The image served up in the Kestrel was gorgeous, pin-sharp across almost the entire field, with beautiful contrast and nary a sign of any internal reflections. This will make an awesome Moon glass! As usual, I noted that the Moon remained sharper when glassed horizontally than vertically; again very normal behaviour for a binocular.

Round about a quarter to local midnight, the sky had gotten sufficiently dark to make out the familiar asterism of the Plough high in the northwest. This afforded a perfect opportunity to estimate the size of the field of view. Well, I was able to hold Phecda and Merak in the same binocular field, which I estimated to be 7.9 angular degrees apart, with a tiny sliver of open sky available before it reached the field stop. Thus, I was confident that the ~8.0 degree field I measured was close enough to the quoted 8.1 figure stated in its official specifications. What is more, I glassed the bright orange star, Arcturus, high in the west-southwest, carefully examining the sharpness of the stellar image as it moved from the centre of the field all the way to the field stop. The results were good here too; Arcturus remained nice and pin sharp across most of the field with only the outer 10 per cent showing significant distortion, but there was no ballooning of the star like some inferior models I’ve glassed with in the past. That said, I was still able to play with the focus a little to tidy the image up somewhat at the edge of the field. All in all, I came away convinced that this would make an excellent star gazing glass. I can’t wait to use it later in the summer when truly dark stars return to our shores.

Conclusions

There are good reasons why the 8 x 42 configuration is considered the darling glass for birders, hunters and general nature observers. The extreme comfort with which it meets with your eyes, moderate weight and great low light performance are just a few reasons why they have proven so popular. The Viking Kestrel 8 x 42 is packed full of hi-tech optical features and has very solid mechanics that will ensure it will serve you well for many years. The quality of the image is so good that it will rival those served up by models costing many times more. Indeed, if you’re saving up for a premium glass, I would strongly recommend you try this model first.  It could well be all the binocular you really need!

As you can see from reading the string of reviews posted at the beginning of this blog, the testers were pretty much unanimous in their praise of this extraordinary binocular, and for a retail price of just over £200 UK, I feel it represents exceptional value for money. Indeed, one reviewer thought that the Kestrels were the real winners from the entire Viking Optical range, especially when you consider bang for buck. What’s more, so far as I can tell, the more expensive Peregrine range (retailing for just over £300 UK) are distinguished from the Kestrel only in terms of weight and field of view. The Peregrine tips the scales at 600g, so shaving off about 15 per cent of the weight of the Kestrel, but it also has a smaller field of view (7.0 vs ~ 8.0 degrees). To many enthusiasts, these alterations will probably make little or no difference to their viewing enjoyment, so I would recommend you try the Kestrel before considering the Merlin or Peregrine models from the same company!

It really is a steal!

Viking Optical also has a solid reputation for repairing binoculars and this is yet another reason why it is an especially attractive option for British twitchers, in particular. If something should go wrong with your Viking binocular, you can be confident that their technical staff will repair it if it’s under warranty or, failing that, for a reasonable fee. And that’s very good to know!

Highly recommended!

 

 

Neil English is an avid glasser and telescopist who is firmly on the side of the money conscious consumer. If you like his work, please support him by buying one of his books. Thanks for reading!

 

De Fideli.