Astronomy is an absolutely unique and exciting hobby that literally lets you explore the universe. You may think you'll need a telescope to enjoy it, but in reality, there are advantages to using binoculars instead. However, with so many options on the market, choosing the right pair can seem complex, so endless are the possibilities. In this article, we'll review several binocular selections: the best binoculars for astronomy, the best binoculars at budget and, for novices, the best binoculars for discovering the pleasures of astronomy.

Why use binoculars for astronomy?

If you've never used binoculars to observe the sky, you might think that their effectiveness is limited, when in fact this is not the case. Think of all the things your eyes can see. You see a lot more than just the moon and stars, don't you? For example, you can observe planets, star clusters, nebulae and even galaxies! Now imagine all the other things you could observe with binoculars.

Binoculars may not be as powerful as a telescope, but they can already help you discover many more elements of the celestial vault, impossible to distinguish with the naked eye. Most of the cosmic wonders you've heard about are too difficult to see with the naked eye, but will be visible with even modest astronomical binoculars.

What's more, binoculars are lightweight, so you can take them with you wherever you go and use them effortlessly. Has the sky temporarily cleared? Then you can quickly grab your binoculars and make the most of the time you have left before clouds obscure the view.

Binoculars are also ideal for astronomy beginners, as they allow you to practice spotting what you want to observe before investing in a telescope. This way, you'll have a good idea of what you can observe and how to find it; after all, if it's visible with binoculars, it'll be even more visible with a telescope!

Finally, there are two other essential advantages. You can easily use them during the day (unlike astronomical telescopes, which, by the nature of their design, aren't really suited to this use) and, finally, binoculars generally cost less than a telescope.

How to choose the right astronomical binoculars?

That being said, before you buy your astronomical binoculars, knowing more about certain features specific to binoculars will help you make the right choice, including:

• Magnification and objective diameter
• Lens coatings and prism types
• Binocular configuration

There are, of course, a few other technical details, such as exit pupil, eye relief and field of view, but the three key points mentioned above are already a good starting point. Let's take a quick look at each of them and see how they can influence your decision.

Lens magnification and diameter

You've probably already seen binoculars marked with a two-digit number, e.g. 10×50. Of all the information you need to know, these two numbers are undoubtedly the most important. In fact, the first number describes the magnification or approximation, and the second the lens diameter.

Magnification is self-explanatory. However, high magnification won't do you much good without a lens with the right diameter. The latter refers to the diameter of the lenses that point at your target. Measured in millimeters, the larger the lens diameter, the more light your binoculars can gather.

Why is this important? Binoculars with a larger objective diameter will enable you to observe less bright targets and see more detail. For example, with 70 mm binoculars, you'll see more stars in a star cluster than with 50 mm binoculars.

In this case, magnification plays a less important role. Let's imagine you have two pairs of binoculars, one 10×50 and the other 20×50, and you use them both to observe the same star cluster. With 20×50 binoculars, the star cluster will certainly appear twice as large, but you won't see any more stars than with the other pair, because the diameter of the lens, and therefore its ability to collect light, is the same.

So you may prefer to buy binoculars with larger-diameter lenses. Bear in mind, however, that the larger the lenses, the heavier the binoculars. Binoculars with larger lens diameters are ideal for astronomy, but their weight can quickly lead to arm fatigue and often requires the use of a tripod.

In fact, the upper limit for the objective diameter of pocket binoculars is around 70 mm. While many amateur astronomers will opt for 15 x 70 binoculars, for beginners 10×50 binoculars are an excellent choice, both for astronomy and for more general use. Above 70 mm, the use of a tripod is usually recommended for reasons of comfort.

Lens coatings and prism types

Binoculars use a combination of external lenses and internal prisms to produce the view you see when looking through the eyepieces. These optical instruments are coated with anti-reflective compounds, with the aim of reducing imperfections and improving vision. Although there are many types of coating, the two most common are Multi-Coated (MC) and Fully Multi-Coated (FMC).

If lenses have been treated with a multi-layer coating, this means that at least one of them is coated with several layers applied to at least one of its faces. These are usually the outer sides (the side of the lens in contact with the air) of the lens.

In the case of full multi-coating, the lenses are coated on all sides. Depending on the manufacturer, prisms may also be multi-coated.

As a general rule, the more layers a lens has, the more efficient its light transmission. For example, fully multi-coated lenses and prisms generally have a light transmission rate of around 95%, giving you excellent results.

Another factor to consider is the type of prism. There are two commonly used: BK-7 and BaK-4. Since BaK-4 prisms are made from higher-quality glass, the image they reproduce will be all the better for it.

However, while it's preferable to choose binoculars with full multi-coating and BaK-4 prisms, note that the price of these models will be a little higher. If you're new to stargazing with binoculars, models with multi-coated lenses and BaK-4 prisms are just right for you. However, we recommend that you avoid BK-7 prisms, as they can produce rainbow effects (known as "chromatic aberrations") around bright objects, as in the case of the Moon.

Binocular configuration

When you think of binoculars, the image of traditional Porro prism binoculars certainly comes to mind. They are W-shaped, with the eyepieces slightly offset from the glasses. When light enters through the objective and its lenses, it passes through the prisms and is refracted towards the eyepieces.

More recently, manufacturers have developed roof prism binoculars in the shape of an H. The bezels of these models are completely straight and require a more complex arrangement of prisms to refract the light to the eyepieces.

Traditional Porro (W) prism binoculars produce better image quality. However, they tend to be heavier. Roof prism binoculars (H) are lighter and are particularly suited to outdoor use, such as hiking. Image quality may be slightly poorer, however, and they tend to cost a little more. Generally speaking, Porro prism binoculars are best suited to astronomy, while roof prism binoculars are more suitable for general use.

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