A Work Commenced January 24 2025

Having throughly enjoyed a world-class 10 x 50 binocular for stargazing, in the embodiment of the Sky Rover Banner Cloud, for some time now, I began to wonder what a step up in aperture and magnification might do for studying my favourite deep sky objects. I’ve had some limited experience with Celestron’s  entry-level large binocular: the SkyMaster 15 x 70. This basic instrument revealed some showpiece objects in the night sky such as, the Pleiades and the Orion Nebula in amazing detail: far more, in fact, than any 10 x 50 could show. But it had its drawbacks. For one thing, only the central 50 per cent of the field was acceptably sharp. The build quality wasn’t the most robust either. Long term use would likely result in the barrels losing collimation, and I was also conscious that the binocular was not operating at its advertised aperture of 70mm – more like 63mm in fact. 

That led me to try out a number of other models to assess their optics and build quality. The first model I tested was the Celestron SkyMaster Pro 15 x70. Retailing for £215, or twice as much as the entry-level SkyMaster model, it sports a much more robust build quality. Performing a flashlight test, by directing torch light through the eyepiece and measuring the diameter of the circle of light projected out from the objective indicated that it was indeed operating at its full 70mm aperture.  However, after mounting the instrument on a sturdy Oberwerk 2000 monopod with its excellent trigger grip ball and socket mount, my impressions of its optical performance strongly suggested that it had the same optics as the basic non/pro model. Stars viewed within the inner 50 per cent of the field of view were crisp and sharp but showed the same distortions as the entry level SkyMaster 15 x 70 model in the outer portion of the field. This was disappointing to me as I did expect an improvement in optical performance for this price hike. 

I was also less than impressed by the supplied soft carry case, which I judged woefully inadequate to store the instrument for the long term. This class of instrument definitely deserves a proper carry case if it’s going to be used  regularly. 

Next, I bought in the Opticron Oregon  20 x 80. Retailing for just £159, I was delighted to see that the instrument came in a sturdy, black foam-lined case. I was also surprised by its relatively light weight, tipping the scales at 2.2 kilos. The focus wheel was very smooth and responsive with no free play. Conducting the same torch light test showed that it too was not operating at its full 80mm aperture but only at 74mm, a result in keeping with astro binocular author, Stephen Tonkin, who measured his unit at about 75mm. 

Optically, the unit I acquired performed very well indeed. Even though it has a smaller field of view than the lower power Celestrons at just 3.2 degrees, it showed a much larger sweet spot, with 80 per cent of the field displaying pin sharp stars and even at the edges, stars remained acceptably well presented. Indeed, this 20 x 80 showed me arguably the finest view of the Andromeda Galaxy(M31) I have yet seen in any telescope or binocular. The big 80mm Opticron Oregon represents excellent bang for buck, and is recommended for those on a strict budget. For me though, it raised the same issues I had with the entry-level SkyMaster 15 x 70: under sized prisms and overly light build quality. Still, I was in two minds about letting it go: the views I had of M31, M33, the Sword handle of Orion and the Pleiades, were superb! That extra magnification and smaller exit pupil presented lovely, dark sky hinterlands with sparkling starlight filling the field of view.

Mindful of acquiring high quality optics and a robust build quality, I chanced upon a lightly used Helios Apollo 15 x 70 for a good price and pulled the trigger on it. When it arrived in its custom aluminium hard case, I was mightily impressed by its excellent build quality. This is one chunky binocular weighing in at 2.45 kilos. It has a thick rubber armouring and a fully broadband optical specification. The significantly increase in bulk is attributed to its full size prisms, which deliver extremely bright and sharp images across its 4.4 degree field. Further research indicated that its light transmission is a whopping 94 percent! 

Unlike the usual centre-focus of the aforementioned binoculars from Celestron and Opricron, the now-discontinued Helios Apollo 15 x 70 comes with individually focusing(IF), eyepieces, which take a bit of getting used to! But with practice it becomes second nature.

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Having to individually focus each eyepiece makes watching wildlife in the near and middle distance quite challenging but for fixed targets it’s not a big issue. The Helios excels at studying targets over long ranges where substantial changes in position can be enjoyed without refocusing. Optically, it’s a good step up from either the Celestron or the Opticron, showing more punchy, higher contrast images with noticeably better control of chromatic aberration. 

The Helios Apollo really struts its stuff under the stars though, where all targets are effectively at infinity. That said, there is a slight difference in best focus when observing celestial targets at low and high altitude. I quickly found that I could achieve a workable compromise here simply by setting the focus on stars situated at mid-altitudes. Views of the showpiece celestial objects are very impressive in the Helios Apollo. It serves up the same 4.4 degree field as the Celestron but exhibits a much larger sweet-spot. That said, performance beyond about 70 per cent of the way from the centre falls off very quickly, so much so that stars at the field stops are quite distorted. Still, I found the quality of the views noticeably superior to the Celestron and I enjoyed many hours studying the Beehive Cluster, the Open Clusters, M35 , M36, M37, M38, the Sword Handle and Belt Stars of Orion. Kemble’s Cascade is beautifully presented within its modest field. The Double Cluster is a mesmerising sight high overhead on a dark winter’s night. Centring Alpha Persei in the field of this big binocular reveals a blizzard of stars shining across the cold, dark of interstellar space. You can spend countless hours panning the winter Milky Way from Monoceros in the south to Cygnus low in the north. 

Having said all that, all these binoculars have their limitations. For one thing, chromatic aberration can prove bothersome to more than a few individuals. Having enjoyed a new breed of ultra flat field binoculars with ED glass prescriptions in smaller apertures, I can immediately see why a wider, flatter field would appeal to many observers of the night sky. Thankfully, there are welcome signs that this market, once the preserve of premium, so-called ‘Alpha’ brands, is now experiencing revolutionary new models from Sky Rover and Oberwerk, for example, which incorporate extra low dispersion glass and field flattening optics, can now be purchased at prices that won’t break the bank. And based on my experiences with this trio of binoculars, I can readily see one of these new models having a permanent home in my binocular arsenal. 

Watch this space!

Read more about binoculars of all genres in my latest book, Choosing & Using Binoculars: A Guide for Stargazers, Birders and Outdoor Enthusiasts.

De Fideli.