Comparing Six 10×50 Roof Prism Binoculars

Credit: Alan Dyer

For astronomy, a pair of 10x50s represents the ideal combination of good aperture (50mm) for bright images, with enough power (10x) to nicely resolve star clusters and reveal galaxies, and yet still be light and easy to hand hold for convenient scanning of the sky.

I find that roof prism 10x50s, though more expensive than traditional – and typically low-cost – Porro prism models, offer optics that are often just that much sharper. Stars appear more like points lacking the “spikiness” from residual aberrations in lesser optics. Internal focusing is smooth and precise, with no wobbly bridge connecting the eyepieces as in Porros, and with the central focus knob easier to reach with gloves on. As you go up the price range the field of view widens, as does sharpness across the field.


In this survey I looked at models from $200 to $500, putting them in the low- to mid-range price classes for roof prism binoculars. I present them in order of increasing suggested U.S. retail price, though they might sell for less at some outlets.

Nikon ProStaff 5

Nikon ProStaff. Credit: Alan Dyer

Pros:    Lightweight; long eye relief; low price

Cons:   Some false color; lesser grade coatings; eyecups collapse easily

The ProStaff 5 is one of Nikon’s entry-level roof prism series. It is above the economy ProStaff 3S in price, but below the ProStaff 7S (with phase-corrected coatings on the prisms), and well below Nikon’s premium Monarch series. However, only the ProStaff 5 line offers a 10×50 roof prism model (not counting Nikon’s $6,400 WX!).

Without extra-low dispersion (ED) glass, false color fringing is obvious, but stars are sharp in the central 60 percent of the measured 56° apparent field of view, matching the published specs. Eye relief is the longest of the group, at a superb 20mm. Upon inspection, the coatings are not up to the other models, with the ProStaff’s main lenses exhibiting the brightest reflections of the group. Nevertheless, starfields looked impressive with good contrast, and the field uniformly bright to the edge.

The body is durable polycarbonate, making it the lightest of the 10x50s I tested, at 30 ounces (830 grams). The matte-finish armor coating provides a secure grip. With their light weight, the ProStaffs are comfortable to hold, with a smooth focus mechanism that worked well in sub-freezing temperatures. However, the twist-up eyecups collapse too easily when pressed. There is no 1/4-20 socket for mounting a tripod adapter and the lens caps are loose and thin plastic. The minimum interpupillary distance is 56mm, similar to Celestron’s Nature DX and Granite ED, and tighter than the other models tested. This spec will be of value to anyone with closely set eyes or for use by children.

Bottom Line: A good low-cost, lightweight and comfortable binocular to use.

MSRP: $200



Celestron Nature DX ED

Celestron Nature DX ED. Credit: Alan Dyer

Pros:    Little false color; long eye relief; solid eyecups

Cons:   Narrowest field of view, along with Nikon ProStaff

Celestron’s Nature DX ED series of binoculars offers long eye relief and very good optics for the price. The 10×50 DX ED exhibited a similar 56° apparent field of view as the ProStaffs, slightly less than the advertised 59°. (By comparison, Celestron’s lower-cost Outland X 10×50 has a stated 55° apparent field and only 10mm of eye relief, too short for comfort in my opinion.)

Compared to the Nikon, the Nature DX has less false color due to the use of ED glass. Stars are sharp across the central 70 percent of the field, though with a bit of astigmatism on-axis. At the edge of the field, aberrations do bloat star images, and there is a slight darkening, or vignetting, of the edge.

The ribbed focus knob offers a firmer grip than in the higher-priced Celestron Granite ED and so is easier to turn, while the twist-up eyecups hold their position better than in the Nikon ProStaff. However, the body is wider and not quite as comfortable to hold as the tapered bodies of the competitors.

Bottom Line: Excellent performance at the low end of the price range for a roof prism.

MSRP: $220



Vortex Diamondback HD

Vortex Diamondback. Credit: Alan Dyer

Pros:     Wider than advertised field of view; sharp optics

Cons:    Not ED glass; heaviest unit tested

The Diamondback series from Vortex Optics is the next step up from their entry-level and excellent Crossfires. Stars in the 10×50 Diamondback are sharp across 70 percent of the field, and are only moderately aberrated at the edge with minimal vignetting. A bonus is that while the Diamondback is rated as having a 60° apparent field, in my tests it closely matched the 65° fields of the more costly Athlon and Alpen Apex. Though advertised as “HD”, the Diamondbacks do not not have ED glass per se. Even so, false color is minimal. The prisms have high-transmission dielectric coatings but not phase-corrected coatings. For those, move up to the Vortex Viper series at considerably higher price.

The Diamondback’s focusing mechanism is smooth and snaps into precise focus, with the knob extending up high for easy reach with gloves on. These were the heaviest of the 10x50s, but by a small margin. As with all Vortexes, the included padded case is excellent, among the best of the group, and the Diamondback comes with a “GlassPak” chest harness. Vortex’s unconditional warranty promises to repair or replace any binocular even if the damage is your fault, with no receipt required. In all, I consider the Diamondback to be a superb value.

Bottom Line: Near top-level performance at the lower end of the price range.

MSRP: $310



Celestron Granite ED

Celestron Granite ED. Credit: Alan Dyer

Pros:    Sharp optics with little false color; widest field

Cons:   Focus mechanism hard to turn in cold weather; edge-of-field vignetting

The Granite ED line was Celestron’s premium series of roof prism binoculars. However, as of November 2020, after being listed as Clearance models for most of 2020, the Granites are now discontinued. A Granite might be a good choice if available at a used price. False color in the Granite 10×50 I tested was minimal, as expected from its ED glass. Images were sharp across the central 60 percent of the measured 67° field, the widest of the group. But stars were quite aberrated at the edges. At night the field also showed noticeable vignetting at the edges, with the field stop soft. …..

The main drawback is that the focus knob’s surface is far too smooth, making it hard to grip and turn. It is especially tough in winter with gloves on and when the grease in the mechanism stiffens up which, at this price point, it shouldn’t. The front lens caps clip into receptacles on the body, but tend to fall off easily and could be lost.

Bottom Line: Good optics, but focus mechanism is poor for a premium binocular.

MSRP: $450



Bresser/Alpen Apex

Alpen Apex. Credit: Alan Dyer

Pros:    Wide field with excellent optics and focus mechanism

Cons:   Some false color; no index marks on diopter adjustment

New in 2020, the Bresser/Alpen Apex has phase-corrected coatings but not ED glass, and so did show some false color either side of focus on Venus. However, images are very sharp – the phase of Venus was wonderfully crisp. Stars remain pinpoint across 70 percent of the 65° field and are still well contained at the edge, with a cleanly defined field stop and very little edge darkening.

Focus is smooth and precise, and works well when cold. The right eyepiece diopter, while textured and easy to adjust, has no markings to aid resetting to a preferred position. The body has no molded thumb indentations or textured finish to aid gripping, though I found them easy to securely hand-hold. Like the low-end Nikons, the front caps are loose and easily lost. In all, the Apex offers excellent optics and mechanics, though is missing some features of the similarly-priced competition.

Bottom Line:      Sharp optics, though lack of ED glass unusual at this higher price point.

MSRP: $480



Athlon Midas G2

Athlon Midas G2. Credit: Alan Dyer

Pros:    Best optics of the 10×50 group; superb build quality

Cons:   Eyecups don’t extend as far as they should

Also new in July 2020, the second-generation Athlon Midas G2 UHD adds better coatings to protect the outer lens surfaces and has ED glass (what Athlon calls UHD) for minimal false color on bright stars and planets. The prisms feature both phase-corrected and dielectric coatings for maximum contrast and light transmission. Under dark skies, starfields looked stunning with dark nebulas popping out. The apparent field of view is 65°, sharp across 80 percent of the 6.5° actual field, the best of the bunch, with star images well contained at the fully-illuminated edges.

Construction is magnesium alloy and the ribbed finish makes them easy to securely grip. The eyecups, though twist-up, don’t extend up enough to place them on your face with glasses off and seem a little flimsy. However, this was my favorite of the six 10×50 roof prism binoculars I tested. It is the most expensive, though by only a small margin compared to the Apex and Granite, and the “street price” of the Athlon Midas is typically $100 lower. And like Vortex, Athlon’s warranty is unconditional. You break them – they’ll repair or replace them.

Bottom Line:   The best optical performance, with all the expected coatings.

MSRP: $490


See Alan Dyer’s full review of the Athlon 10×50 Midas G2 binoculars here.


Table: 10×50 Roof Prism Binoculars

All have internal central focusing mechanisms and twist-up eyecups. All are claimed to be waterproof, but I did not submerge them to check! Weights are measured with captive front lens caps attached as you would likely use them, so they will differ from published specs. Eye relief is measured from the top of the retracted eyecup, not from the lens. Actual fields of view were measured by looking at starfields; the apparent field figure assumes 10x power.


Model Nikon ProStaff 5 Celestron Nature DX ED Vortex Diamondback Bresser/Alpen Apex Celestron Granite ED Athlon Midas G2 UHD
Weight (g / oz) as measured 830 / 29.3 864 / 30.5 875 / 30.8 858 / 30.2 854 / 30.1 868 / 30.6
Actual Field of View (°) as measured 5.6° 5.6° 6.5° 6.5° 6.7° 6.5°
Apparent Field of View (°) 56° 56° 65° 65° 67° 65°
Eye Relief (mm) as measured 20 17 16 15 16 17
ED Glass No Yes No No Yes Yes
Phase-Corrected Coatings No Yes No Yes Yes Yes
Interpupillary Distance (mm) 56 – 75 56 – 74 60 – 75 59 – 73 56 – 73 59 – 74
Waterproof Yes Yes Yes Yes Yes Yes
Dry Gas Filled Nitrogen Nitrogen Argon Nitrogen Nitrogen Argon
Coatings Multi-coated Fully multi-coated Fully multi-coated Fully multi-coated Fully multi-coated Fully multi-coated
Tripod Adaptable No Yes Yes Yes Yes Yes
Warranty Limited lifetime Limited lifetime Unconditional lifetime Limited lifetime Limited lifetime Unconditional lifetime

About Alan Dyer

Alan Dyer is an astrophotographer and astronomy author based in Alberta, Canada. His website at has galleries of his images, plus links to his product review blog posts, video tutorials, and ebooks on astrophotography.

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