Three Achromatic Binoculars.

Three achromatic binoculars.

A work commenced April 16 2021


Over the last decade I have dedicated much of my free time to educating the amateur community on the great achievements of the classical achromatic refractor. My 650 page historical work, Chronicling the Golden Age of Astronomy, documents many of the amazing achievements made by highly skilled individuals over many centuries who used these great telescopes to divine pretty much everything amateur astronomers explore today. And despite what some claim regarding the newer refracting telescopes that employ extra low dispersion(ED) glass, this modern development represents, at most, a mere footnote to the true history of these telescopes.

But it is not the classical refractor that best exemplifies the wonders of crown and flint, but the humble binocular. I have had the pleasure of looking through many of these fine instruments and have been astounded at the wonderfully sharp and clear views they serve up. And even in this era of extraordinary technological development, I’m especially delighted to see that crown & flint is alive and well in a suite of state-of-the-art binoculars that carry on that legacy into the 21st century.

This blog will describe three such instruments that fulfil all of my binocular needs; the Leica Ultravid 8 x 20 BR, the Barr & Stroud Series 5 8 x 42 and the Pentax PCF WP II 20 x 60.

The Leica Ultravid 8 x 20 BR

The extraordinary Leica Ultravid 8 x 20 BR.

This tiny optical marvel has transformed what I understand an ideal daytime binocular to be. This state-of-the-art instrument uses no ED glass, yet achieves a level of optical excellence that really needs to be experienced to be believed! The following sentiments are contrary to what you will read from almost every other binocular enthusiast, but they are solidly grounded in both optical theory and field experience. For daytime use and for much of the year, the size of your eye pupil is very small, typically between 2 and 3mm. This means that using binoculars with larger exit pupils (calculated by dividing the aperture of the binocular by its magnification) wastes a lot of the light collected by larger binoculars usually touted as being ideally suited to daytime use – I’m thinking of those with objectives sizes of 32 and 42mm in particular. But there is another, perhaps even more important reason for choosing these smaller exit pupils – image sharpness. When you are sampling the image with a smaller exit pupil you are employing the best part of your eye lens to bring that image to focus. And when you couple this optimal image sensor(itself a marvel of Divine creation) to an optically excellent binocular, you have a match made in heaven!

Thanks to the incorporation of the latest in coating technology into this small binocular, including phase corrected prisms, aspherical eyepieces, and multiple layers of the best anti-reflection coatings on all glass surfaces, this small 20mm aperture instrument serves up impressively bright and high-contrast images across the entire field of view. Leica optics are the contrast kings, being world leaders in suppressing stray light and internal reflections, including veiling glare, which is a particularly pernicious problem in many binoculars, however the size. The image just snaps to focus with none of the ambiguity you all too often get with binoculars of lesser quality. The mechanical build quality and ergonomic handling of this binocular are also superb, being designed for a busy life in the great outdoors. Only at dawn and dusk does the limitations of its small aperture become apparent, but these are times I do not normally glass, so these shortcomings are rarely encountered.

The Leica Ultravid BR 8 x 20 is very compact and lightweight(245g), fitting in any pocket. You can wear it ’round your neck all day and never experience neck strain. Try doing that with an 8 x 42 or even an  8 x 32! Employing a dual-hinge design, squaring on with the eye pupils takes a little more care to get right, but with practice this becomes easy. And because the collimation and robustness of the binocular is second to none, you don’t experience eye strain, blackouts or headaches even after prolonged daily use. But another hugely important factor for many glassers, including yours truly,  is its cost to performance ratio. You get sublime Leica(alpha) quality at a fraction of the price of buying larger alpha binoculars. And because it works so well, my encounter with the little Leica Ultravid saved me a small fortune. I’d have to shell out more than a £1000 more to get a larger instrument of similar optical quality.

The Leica Ultravid BR 8 x 20 goes everywhere with me. I use it for birding with its generous 6.5 degree true field, examining objects at close distance(less than 2 metres) both indoors and out of doors, surveying the landscape, whether in a rural or urban setting, and I look forward to being able to visit theatres, museums and classical music concerts in the future with it, as the country opens up for life as normal. I have even used it productively observing the phases of the Moon at night. I would highly recommend this to readers who are wanting the best optical quality at a price that is considerably lower than going the traditional- think heavier – route. It certainly works for me!

The Barr & Stroud Series 5 8 x 42 

The Series 5 8 x 42; a wonderful, cost-effective instrument to study the starry heaven.

As binoculars move from pocket to mid-size formats, they become easier to make well, owing to less stringent design tolerances. The Barr & Stroud Series 5 8 x 42 is a solid, mid-tier binocular that I use for general stargazing. Its larger 42mm objective lenses collects far more light than the Leica 8 x 20, and produces impressive wide field images of the night sky. It is also often employed observing the Moon, especially when clouds pass over it in the sky, producing wonderful, colourful light shows. Ergonomically, the Series 5 is easy to handhold for considerable periods of time, and with its very well corrected 8 degree true field of view, it’s a superb tool for scanning the Milky Way and observing larger deep sky objects such as the Pleiades, Hyades, the Sword Handle of Orion, the Beehive and Coma cluster, the Double Cluster in Perseus and the Great Andromeda Galaxy, to name but a few.

The Series 5 has a light-weight magnesium chassis, a silky smooth focuser – one of the best I’ve encountered, in fact, in a binocular in this price class – and very decent optics. Its very large field is very well corrected – a lot better than many other models I’ve sampled in this price range – with stars remaining satisfyingly sharp even near the field stop. The metallic twist-up eyecups overlaid with soft rubber are of high quality and maintain their positions well, affording an exceptionally comfortable viewing experience. And though I don’t use it much during the day, the Barr & Stroud Series 5 has excellent contrast with very aggressive control of veiling glare. Indeed, internal reflections are also exceptionally well controlled so that it can be used to observe well lit scenes at night without showing up annoying internal reflections and diffraction spikes.

When I want the steadiest views I can place it on a lightweight monopod or tripod to coax out the maximum amount of detail from a celestial scene. Indeed my own experiments show that when tripod mounted it can detect stars as much as a magnitude fainter than when hand held.  Overall, it fits the niche I have made for it very well indeed, and without breaking the bank.

The Pentax PCF WP II 20 x 60

Excellent bang for buck: the Pentax PCF WPII 20 x 60.

The Pentax PCF WP II 20 x 60 is my very economically priced, high power binocular that functions in much the same way as a spotting ‘scope during daylight applications when I need greater magnifications to see stationary objects better at an extended distance, such as a small bird or a distant landmark. Though conventional spotting ‘scopes do employ a greater range of magnifications(typically 15x to 50x), the 20 x 60 allows me to use both eyes, which is a big advantage over a regular monocular ‘scope and somewhat makes up for the lack of power at the higher end of the magnification scale. Unlike a dedicated spotter, it can be stably mounted on a monopod( that can be collapsed telescopically), which is easier to carry about than a regular spotting ‘scope mount

This large Pentax Porro prism binocular is fairly lightweight for its specifications – just 1.2 kilos in all – so it’s rather easy to mount on a tripod or even a monopod for steadier views. The optical quality of this large achromatic binocular is very good, thanks to its fully multicoated specification and excellent baffling, which ensures very good light transmission in high contrast. Just like the Leica Ultravid, this Pentax also sports aspherical ocular lenses, which serves up a very well corrected vista, right to the edge of its 2.2 degree field of view. As one might expect from a binocular of this specification, it does show a little more chromatic aberration on high contrast targets but it’s never enough to be intrusive. As with the Leica Ultravid, this binocular has a small exit pupil of just 3mm so it’s widely lauded sharpness among its many enthusiasts may well be attributed to this design feature as well. Indeed, as I’ve noted before, this may well have been the aim of the designers of the legendaryTakahashi Astronomer(limited edition) 22 x 60, which has an even smaller exit pupil and field of view(2.1 angular degrees).

The 20 x 60 presents the Moon in stunning detail, with wonderful contrast and sharpness and only a sliver of secondary spectrum seen at the edge of the orb.. Indeed it is one of my favourite instruments to study its changing phases, from slender crescent right through to full phase. Selected deep sky objects such as the Pleiades, the Andromeda Galaxy, the Beehive Cluster, the Orion Nebula and large Messier open clusters like M36 through M38 in Auriga, as well as M35 in Gemini can be observed in glorious detail with this nifty instrument, with stars remaining sharp and undistorted right to the field stop.

Sometimes, I like to use the Pentax 20 x 60 to study colourful star fields and wider double and multiple stars. I’ve enjoyed stunning views of the Garnet Star, Mu Cephei, the lovely colour contrast pair, Albireo, as well as O1 & 2 Cygni, and the orange dwarves comprising 61 Cygni. Indeed, the sky is chock full of widely spaced binocular doubles well within the reach of this powerful binocular. It could keep you going for years!

I also employ the 20 x 60 to conduct all of my solar observations, recording sunspots using a pair of homemade white light solar filters. It produces the right combination of image scale, contrast and resolving power to get the job done. In addition, I may use it to search for and/or observe brighter comets which grace our night skies from time to time.

I have often thought about going larger in terms of light grasp, perhaps with a 70 or 80mm binocular,  but this would severely limit its portability and mine too. Thus, I regard the 20 x 60 as being at or near the limit of where I’m willing to go with two eyes, before I switch to monocular vision with my astronomical telescopes.

Well, as I bring this blog to a close, I hope you will more fully appreciate the choices I have made in pairing down the binoculars I intend to use in the coming years, and hope that it inspires you to find your own path through the complex binocular maze. There is a great satisfaction in finding the minimal set of instruments that fulfil all the requirements of a busy life in the great out of doors, a set of instruments that don’t cost the earth and yet satiate every desire I could wish for them. I used to enjoy perusing the colourful adverts of all kinds of binoculars in the glossy birding magazines, but these days I tend to ignore them; they just don’t offer any temptations that I would want to pursue, and that’s a good thing in my opinion!

Thanks for reading!


De Fideli.

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