Think about back-garden astronomy, and binoculars immediately come to mind. They're portable, cheaper than a telescope, and give you a great view of the heavens. There is another alternative, however, the monocular. Essentially a pair of binoculars cut in half and benefit from being lighter, and are often much simpler devices than binoculars, being only a single barrel with one objective lens.
Monoculars are often considered a portable and travel-friendly alternative to a small telescope, though they don't provide the same level of magnification. They’re often associated with bird-watching, hunting and hiking, though a good monocular can be used for astronomy too. If you're serious about stargazing, you'll need to stick to the best telescopes or a set of good binoculars, but if space and weight are issues, there are good monocular options out there.
When choosing a monocular for astronomy use, you’ll want to be looking at 40-50mm objective lenses, along with 7-15x magnification — anything smaller is better suited to wildlife spotting. Some monoculars have built-in image capture, others offer smartphone mounts for super-easy ‘digiscoping’ and a built-in tripod mount.
Since you’re going to be using them outside it’s wise to choose a monocular that boasts waterproofing and fog-proofing, too, especially as you’ll likely be pulling it out of a warm bag or pocket to use in colder air. Here at Space.com, we've cast our eye over the market for the best monoculars and rounded up the essential picks for all kinds of astronomy.
Best monocular overall
Opticron's BGA WP 8x42 is a great choice for a stargazing monocular, with its 42mm objective lenses letting in plenty of light while also keeping the unit small for backpacking. The 8x magnification (a 10x model is also available) is similar to that on many pairs of binoculars and gives a great view of sections of the night sky.
The Opticron BGA WP 8x42 is waterproof to 3m and nitrogen-filled, so fog-proof, and it comes with a handy leather carry case and a neoprene carrying strap, plus a rubber eyecup that makes it easy for glasses-wearers to use. Thanks to the Opticron S-type multi-coating on the optical system it boasts plenty of contrast, clarity and a definite high-end feel. Sadly a wraparound mount (opens in new tab) is required to make the Opticron BGA WP 8x42 compatible with tripods.
Best for weight saving
There are few better options for travelers who want to enjoy the night sky while out and about than this 10x42 monocular. It’s as lightweight as possible at a mere 11.5 oz/325g.
Not that the Hawke Endurance ED 10x42 doesn’t have some heavyweight glass. It’s fitted with Hawke’s System H5 optics, with extra-low dispersion (ED) glass to reduce color fringing and multi-coated lenses.
It is built to withstand the elements. It comes with a waterproof chassis, high grip armoring, protective lens case, lanyard, lens covers and a built-in 1/4-inch tripod thread. It also comes with a no-fault lifetime warranty.
Best for glasses wearers
Nitrogen-filled to eliminate fog, and waterproof, the Opticron Oregon 4 PC 8x42 is a rugged monocular for anyone who wants a better view of the night sky. It has 42mm objective lenses allowing just enough light in for general astronomical use, and the 8x magnification guarantees you a good (and stable) view when sweeping across the night sky.
The roof prism design is all about wide-field viewing and top-quality optics. With its phase-corrected prism coatings and multi-coated optics, the Opticron Oregon 4 PC 8x42 delivers clear, crisp views by day and in low light. The monocular incorporates an external focuser for easy single-handed operation, though it does lack a built-in 1/4-inch tripod adaptor. Wearers of glasses will appreciate its very generous 22mm of eye relief.
Best for accessories
The Legend lives up to its name, with exceptional optics, build quality and extras. The magnification of 10x, coupled with 42mm objective lenses, means crisp, detailed images enhanced by Bushnell’s ED Prime HD glass, together with multi-coated and anti-reflective optics.
As a bonus, its twist-up eyecups offer plenty of eye relief for those who wear glasses, and there’s even an easy-to-grip ridge on top of the external focuser where your thumb would naturally rest.
The Bushnell Legend Ultra 10x42 stands out from its competition by shipping with a top-quality padded case complete with a belt clip, a flip-style lens cap for the front, and a rear lens cap that attaches via a lanyard to prevent it from getting lost.
Best for magnification
If you want to zoom in on anything, including the night sky, with your smartphone the only method in common use, at least until periscope-style zoom lenses become common on cellphones, is to use a digital zoom. This means cropping the image, then rebuilding it to its original size using algorithms or machine learning. It almost always results in a poor-quality image.
A far better option is a clip-on lens like this BAK4 roof prism-based monocular, for its superior optics. Essentially a small telescope with a fixed zoom of 36x, the Apexel 36x superzoom can be used hand-held but is best on a tripod. You fit a clip around your smartphone’s existing lens before attaching it to the Apexel 36x super zoom to bring them into alignment.
It’s not perfect, since you first need to remove your smartphone’s case, there’s no tripod thread built-in (a metal tripod ring adaptor is supplied) and in any case the tripod it is bundled with is pretty flimsy. Supply your own tripod, however, and the Apexel 36x superzoom can be an adequate setup for taking basic images of the Moon (though don’t expect it to fill the field of view). It can also be used as a monocular by attaching a small rubber eyepiece, though the field of view is restricted.
Best for using with a smartphone
The act of attaching a cellphone to a telescope so that the phone's camera can peer down the barrel and see the view in a much greater magnified way is called digiscoping. The camera can produce some excellent images of distant ducks during the daytime and of the night sky at night.
The Celestron Outland X 10x50 comes with a smartphone mount and could be seen as an ideal digiscoping companion, with its astronomy-centric optics. The 10x magnification and 50mm objective lenses are well-suited to searching for, and studying, open star clusters, the Moon, and the Milky Way.
Built around BAK-4 prisms, the Celestron Outland X 10x50 feature multi-coated optics and have plenty of eye relief, so can be used easily by anyone who wears glasses. It’s also waterproof and filled with nitrogen gas to prevent internal fogging.
Best for travelling light
A zoom monocular capable of magnification from 8x to 42x, the Olivon 8-24x40 is capable of both observations and basic photography. Its magnification is great for observing the Moon’s craters and lava seas, while it's small and light enough to take traveling.
A BK-7 prism-based monocular with a push-pull zoom arrangement, it comes with a built-in 1.4-inch tripod adaptor to help keep it stable, an easy-grip rubberized coating and multi-coated optics, and can also be used as a basic digiscoping option. When used for wildlife spotting, the Olivon 8-24x40 offers close focus from 60”/1.6m. It comes with a lanyard and a small pouch.
Best for Moon-viewing
A slightly more expensive option than the aforementioned Olivon 8-24x40 is the Orion 10-25x42, another variable zoom monocular that offers 10x through 25x magnification and has a slightly larger objective lens.
As such it’s another great option for lunar viewing, with just a touch more magnification than its lighter rival. Since it doesn’t have quite as wide an angle of view it can focus on subjects just 20”/50cm away while also offering 25x magnification for glimpsing craters on the Moon, making it very versatile for day or night time use. It’s also usable during low-light thanks to its 42mm aperture objective lens.
The Orion 10-25x42 is waterproof, with a rugged, rubberized design, and features multi-coated optics. It ships with a soft nylon case (complete with belt loop) and a wrist strap.
Best for wildlife
It's always tempting to go for the biggest magnification when looking at a new optical instrument, but this isn't always the best choice as it adds weight and requires larger objective lenses to maintain a bright view and use at night. Moderate magnification factors of around 8x are therefore preferred.
The 15x magnification of incredibly expensive Vortex Recon R/T 15x50 will give you a much closer look at objects than your average pair of astronomy-centric binoculars or monoculars. However, at night, that extra magnification creates a narrow exit pupil which reduces the brightness of the image, despite the Vortex Recon R/T 15x50’s large 50mm objective lenses.
So what is the Vortex Recon R/T 15x50 for, in terms of night-sky viewing? The Moon. With its multi-coated extra-low dispersion glass, you can expect detailed and high-resolution images at long distances. A nice detail is that it comes with a hand-strap but also with a carry clip that attaches to a belt, clothing or a bag.