Binoculars for Astronomy

There are many reasons why Binoculars make an ideal choice of equipment to observe the night sky and not just for beginners. Many seasoned Astronomers will also testify to using Binoculars alongside their larger Telescopes because the simple fact is that some deep space targets just look better when viewed (in stereo..so to speak!) with both eyes using Binoculars.

In this article we will explore the different Binocular spec, their advantages and disadvantages as well as what kinds of interstellar objects you can see with them.

When do Astronomy Binoculars make sense:

This question is easy for beginners as Binoculars are generally more affordable for someone starting off and are extremely easy to use even for younger Astronomers or kids. If Astronomy has always fascinated you and you think you would like to get a bit more into it, then Binoculars are a great option to explore because even if you progress on to bigger and more complex Telescopes, you will find you will always come back to using your Binoculars at some point.

Binoculars are small, lightweight and can be used anytime and anywhere so whether you’re on Camping trip in the mountains at some dark sky location or even on Holidays, your Binoculars will take up minimal space and will be ready to use for observing the night sky at any time. For much the same reason, even advanced Astronomers find them very enjoyable as certain objects like Star clusters, some bright nebula and even some galaxies look far more impressive when viewed with both eyes, especially with that unique ultra wide field of view that you have when using Binoculars.

You will be amazed, even if you live in a heavily light polluted city because if you look up on a clear night you might only see a handful of stars (maybe around 50 or 60), but using even basic low powered Binoculars, you will go from seeing around 50 or more stars with the unaided eye to seeing several thousands of stars through Binoculars. At a dark sky location, things get even better and even objects like the core of the Andromeda Galaxy M31, the bright stars of M45 Pleiades or even the whispy cloud structure of the M42 Orion nebula core are all visible through most good Binoculars. The Moon will also appear very crisp and sharp with high-power Binoculars and the crater details and some of the larger terrain features will be very clearly visible, appearing very impressive indeed.

As already mentioned, another advantage of Binoculars for Astronomy is the very wide field of view that they provide which also means that finding different deep space objects with a star map or an app such as Stellarium will be so much easier.

An example of just some of the objects visible using Astronomy Binoculars

M31 Andromeda Galaxy

The Moon

M45 Pleiades

Choosing the right Binoculars for Astronomy:

The optics and principles of Binoculars are in essence the same as a telescope and just like astronomy telescopes, Aperture is king and good quality glass lenses are also key to ensuring the best viewing experience. Despite what many people believe, for most deep space objects, magnification is not as important as aperture. As a recap, in case you are unsure what the term Aperture means, it is basically the size of the main glass lenses in the Binoculars and is usually measured in millimeters. This is important because objects in deep space are not very bright due to their extreme distances from Earth and so the bigger the Aperture, the more light the Binoculars can allow through, hence the brighter and clearer the object will appear when viewed through them.

That’s not to say magnification is not important, it helps a lot for solar system objects like the Moon, but the majority of deep space objects that will be visible through Binoculars are extremely faint and so it is generally more important to have a bigger aperture.

When choosing Binoculars you will notice they are generally categorised by two numbers eg. 10x50, 20x80 or 25x70 for example.

1. The first number you see is the magnification strength of the Binoculars
2. The second number is Aperture size in millimetres.

So a 20x80 pair of Binoculars will magnify an object by x20 times and have an 80mm Aperture.

Obviously the larger aperture and higher magnification the better, right? Well..yes, but there is a caveat. Larger aperture astronomy binoculars will tend to be bigger and heavier to hold and you will get tired holding them much quicker therefore finding it much more difficult to hold them steady while using them. In addition to this, the higher magnification will mean that even the smallest shaking movement will also be amplified a lot more, making it difficult to view the object clearly and in this case a Tripod is highly recommended. We recommend any Binoculars used for Astronomy up to a maximum of x10 magnification (eg.10x50) should be fine for handheld use without a tripod, but anything bigger is best used with some kind of a Tripod to keep them steady, as it will make your viewing experience a lot more enjoyable, we promise!

For this very reason, most larger Binoculars come with a tripod adapter already and these have a standard 1/4inch thread meaning they can be attached to any camera tripod very easily.

 

How adjust the Focus on Binoculars:

Just like Telescopes, Binoculars need to be focused to suit the person using them as many of us will have different levels of eyesight or some of us may use glasses. Glasses are not a problem with Binoculars and in fact you don't even need to wear glasses when using Binoculars once the focus is adjusted correctly - The only exception to this is if you have astigmatism, in this case you will need to use your glasses while using the Binoculars.

Generally there are either 1 or 2 focus adjustments on Binoculars. On some models there is a single adjustment in the center of the Binoculars which adjusts both lenses together - these are very straight forward. See Illustration below:

 

On other models however, it is possible to focus each eyepiece separately which can be very useful because most of us will have very small differences in each eyes ability to focus on an object and being able to focus both eyepieces independently means you can enjoy an even sharper view. This is also called the Diopter adjustment on Binoculars.

It really depends on the model of Binoculars as to how this is achieved but on some models the center adjustment focuses the left eyepiece and on the right eyepiece there is a ring which can be rotated to achieve sharp focus on the right side. Or you may have an adjustment ring on both eyepieces instead but the principle is the same and that is to allow you to focus each eye independently before using the Binoculars. See Illustration below:

Although it sounds complicated, focusing Binoculars that have dual Diopter focus lenses is actually very straight forward. Just simply point the Binoculars at a bright star (NOT the SUN), then close your right eye very lightly and focus the left eyepiece, then just do the reverse and close your left eye and with your right eye focus the right eyepiece and thats it - Your done! Although some Binocular designs may differ slightly the principle is the same and full instructions should come with your binoculars.

In Summary:

So in a nutshell when choosing Binoculars, these are some important suggestions to keep in mind:

1. For younger kids or adults looking for a good pair of Binoculars to start off in Astronomy, then anything up to x10 magnification is perfect if you want something thats easy to hold without the need for an additional tripod – These are ideal for viewing Star clusters, comets and even some galaxies and brighter nebula. Even at lower magnifications, much more detail on the Moon will be visible compared to the unaided eye.
2. For something more powerful with more options of things to see and if you don’t mind having to use a tripod, then anything from x20 magnification upwards will be ideal – These will be very enjoyable for viewing the Moon at even higher magnifications and many deep space objects such as fainter galaxies and nebula will be visible in more detail too.

Just like Telescopes, Binoculars are available with different optical elements inside them and these range from ED Glass to Argon gas filled internals to prevent fogging. There are also much more specialised ranges such as the Explore Scientific BT range which can even have interchangeable eyepieces like a telescope for different magnifications but just like Telescopes, the cost of these Binoculars vary considerably and for the purpose of this article we are focusing on the standard type. All of our Astronomy Binoculars are ideal for both beginners and advanced users and all contain very good quality glass elements inside.

We always recommend avoiding cheap Binoculars which contain poor quality glass or even plastic optics as unfortunately you will find that these are completely unsuitable for Astronomy.

Here are some Pros & Cons of Astronomy Binoculars v's Astronomy Telescopes

Astro Binocular PROS:

1. A very affordable way to get into Astronomy.
2. Ideal for younger kids, or adults who are interested in Astronomy as a hobby but don't want to invest in expensive equipment.
3. Ultra widefield view makes viewing deep space objects like galaxies, brighter nebula and even comets a memorable experience.
4. Binoculars require minimal maintenance.
5. Binoculars have virtually no setup time and are ready to use straight away.
6. Very small and can be taken anywhere.

Astro Binocular CONS:

1. Don't have the high magnification power needed for certain Solar System objects like the planets.
2. Not suitable for Astrophotography - However quick photos with a phone are possible using a Tripod.
3. Difficult to use filters.

We hope you found this article useful, and feel free to share it using the social links below. As you can see, despite their limitations, there are many reasons why Astronomy Binoculars just make sense for all levels of Astronomy. If you have any questions or would still like some help or advice don’t hesitate to contact us at sales@horizonastronomy.ie and we would be more than happy to help!

Clear Skies!

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