In addition to a great telescope, a good set of binoculars for astronomy is ideal. There are many reasons why. This article covers binoculars for astronomy, beginners’ best options, and the basics you need to know.
What binoculars are best for astronomy? In choosing astronomy binoculars consider at least a 7×50 in terms of strength. For the best binoculars choose good quality optics and lens coating plus adequate exit pupil value and eye relief (for comfort in use).
Other sizes you’ll see mentioned are 8×56, 9×63, 10×42, 10×50, and 20×80. In the following, you’ll learn why different sizes matter to the user. Also, it’s worth noting here that the larger you go in size, especially with the 20×80, the more you’ll need to use a tripod for support.
Why are binoculars good for astronomy?
Astronomy binoculars are more portable than a telescope, you get to see a wider portion of the sky and view objects in their broader context. Binoculars bought for stargazing can double as binoculars for terrestrial pursuits. All up they are a cost-effective option for kids, beginners, or others keen on stargazing.
Binoculars are useful for helping you find that celestial object of interest. Moreover, they assist in getting you acquainted with the night sky, with the positioning of stars, planets, and constellations.
Astronomy binoculars vs telescope: A set of good quality binoculars will provide you with a wider field of view than a telescope. They are more portable than a telescope. Viewing the night sky with stargazing binoculars means you will see a larger portion of the sky than through a telescope.
Can I look at the moon with binoculars? Binoculars are especially good for viewing the Moon in full detail. Have a pair set up on a tripod to watch the blood moon forming during an eclipse. A view through binoculars will enhance your experience of this rare event.
What can you see with astronomy binoculars?
With a good set of astronomy binoculars, you can see not only planets and features on the moon but larger objects like the double cluster in Perseus and star clusters of the Pleiades and Hyades. Galaxies are also one of the astronomical objects you can see in binoculars better than a telescope, as you will see the object in context, with the black sky around it.
Looking through binoculars
Astronomy Binoculars Buying Guide
Want to know what binoculars are good for astronomy for you. It depends, and this guide is about helping you choose the right ones. Since looking through binoculars for sale can be overwhelming, this guide gives you the ground knowledge you need in choosing binoculars for astronomy, the different features, and follows this up with run-downs of some popular brands.
There are a few things to ponder. If you want the best stargazing binocular experience, it’s worth knowing the following…let’s start with the numbers.
What are the numbers in the specifications for binocular size, e.g. 7×35? These numbers represent the magnification power and the diameter of the objective lenses, respectively. In the 7×50, for example, the smaller number, 7, represents the magnification power and the larger number, 50, is the diameter (mm) of the objective lenses in the binoculars.
Let’s look at the smaller number first.
Magnification power (smaller number)
What is the best magnification power for stargazing binoculars? If you are wanting to buy binoculars for astronomy, a power of 7× is okay and a good start. But the ultimate claimed in magnification is 20×. Having said that, above 10×, handheld binoculars astronomy-wise become uncomfortable to hold and difficult to keep steady.
Even with 7× magnification, astronomy-wise, keeping a set of binoculars steady is a task when handheld. You will need to use a tripod or other methods (see binoculars best ways to steady them below) to stop the shaking and get a clear view.
The thing to keep in mind is that while higher magnification will yield a closer view and more details in the image, you’ll sacrifice your field of view. Basically, as you go up in power the field of view narrows. This is something to weigh up when considering the size of your binoculars.
Binocular Field of View
This is often given as how many degrees that can be viewed or a linear measure of width that can be seen at a thousand yards (e.g., feet @ 1000 yds).
Binoculars offer a wider field of view than a telescope (< 1º) and thus, why they have a purpose in astronomy.
A typical pair lets you see 5 to 8 degrees of sky, about the width of four fingers held at arms length.The Editors of One-Minute Astronomer. 2009
Objective lens (larger number)
The diameter of the objective lenses determines the amount of light your binoculars receive. Simply put, the larger the objective lens the more light gets captured and hence the brighter the image you get to see.
A 50 mm diameter objective lens in binoculars for astronomy is considered a reasonable starting point in binoculars for astronomy beginners or hobbyists. Said to give you a high enough light-gathering ability for astronomical use, this size objective lens is a good place to begin for comfort at least since a larger lens becomes weightier to hold.
Still, more aperture is useful for astronomy. You’ll see fainter stars with a 10×80, for example, than a 10×50. But, the larger the aperture the bigger and bulkier will be the binoculars and this means increased difficulty in keeping them steady. You can use a tripod to help with this (I talk about this further down the page). Keep reading though, there are other factors that you need to consider regarding the objective size, e.g., exit pupil.
There are two binocular types — associated with optical prisms. What do optical prisms do? The purpose of the prisms is to rotate the view the right way up.
The two types of prisms are the roof (Dach) prisms and Porro prisms (Nikon).
You should consider the quality of the glass in the prisms. The optimum type is BAK-4 rather than the more inferior, but satisfactory, BK-7, for example.
Porro prism binoculars have a bent path of light, shaped like a Z. Binoculars with Porro prisms tend to give brighter images than those with roof prisms having the same objective size, magnification, and optical quality. They are therefore more affordable than the roof prism type for similar benefits.
You will notice that the Porro-prism binoculars are bulkier because, in these, the objective lenses and the eyepieces are offset.
In contrast, binoculars with roof prisms tend to be narrow types and make the best compact binoculars. The view through roof prism binoculars is straight through because the objective lenses and the eyepieces are aligned rather than offset.
It’s better to have binoculars with optics that hold the focus out to the edge of the field of view when focusing on an object in the center of that field. It doesn’t have to be perfect – what you don’t want is optics where the edge is way out of focus or highly distorted.
This is to do with the precision of the lens shape.
In modern binoculars, performance in low light conditions, such as twilight, depends on the quality of the optical coatings.
Anti-reflective (AR) coatings work to reduce the amount of light being lost through reflection. In binoculars without AR coating, you can lose up to 5% of light transmitted in binoculars. So the AR coating helps improve light transmission through the binoculars.
Modern lenses are coated with complex multi-layers of anti-reflective material.
To look for anti-reflective coating, pick them up and look at the light reflected in the lenses. According to experienced users, a good AR coating would mean the lenses are dark but with some reflected color. Avoid ones where the lenses appear white or ruby red. A white surface indicates no AR coating and ruby-red a highly reflective coating that limits brightness.
Complexity of AR Coatings
There are different types of AR coatings and manufacturers generally describe these as either fully multi, fully, multi or coating.
Fully multi-coated generally means multiple layers of coating on all lens surfaces. Fully multi is found on high end optics.
Fully coated can mean a thin AR coating on both sides of both the objective lens and the ocular lens systems, as well as the length of the prism.
Multi-coated indicates there are multiple layers of coating, but not necessarily on all lens systems.
And coating suggests a single coating only, usually of magnesium fluorite.
You’ll get a brighter image with the right exit pupil value. This means better viewing in low light conditions and having a full image of an object in your view. So for astronomy binoculars, the exit pupil is more important since you will be using them in low light conditions.
Exit pupil calculation: Objective diameter (mm) over magnification (EP = D/M). So, for example, a set that is 7×50 (that is, an objective diameter of 50 mm and a magnification of 7) will have an exit pupil of close to 7 mm.
When choosing your binoculars, look for a set that has an exit pupil value that is at least equal to the diameter of your dilated pupil at night. Interestingly, what to look for in this instance is age-related.
Your best exit pupil will depend on your age.
For those under 30, the average exit pupil is 7 mm. It reduces with age, so an exit pupil of between 5 to 6 mm might be more relevant for 50 years and older. If you are an older user, to avoid loss of light reaching your eyes (plus unneeded expense), a set of binoculars 7×35 or 7×42 would be better suited for you.
In a nutshell, based on age using the 7 magnification example:
- Under 30 yrs have an average 7 mm exit pupil (7×50 is good)
- 50 yrs and above have about 5 – 6 mm exit pupil (7×35 to 7×42 is better)
This is about comfort and seeing the entire field of view, and can make a difference with holding the binoculars steady.
If you need to wear glasses, look for a minimum of about 16 mm or more. Naturally, it will depend on you and your glasses.
Eye relief length is especially important if you wear glasses for astigmatism. You don’t need to wear glasses if you are near- or farsighted since you can adjust the focus of the binoculars to account for these sight issues.
Eye relief of binoculars is usually between a few millimeters and a few centimeters. When wearing glasses, the longer the eye relief, the better the fit for comfort and the better will be your ability to see the entire field of view.
Zoom or Built In Camera
According to experienced users, a built in camera or zoom doesn’t make the grade if you are wanting a pair of binoculars for astronomy.
There are at least three lenses in each binocular eyepiece. The field lens is farthest and the eye lens is closest to the eye.
Some astronomical binoculars have changeable eyepieces that change the magnification.
Reviews of Best Binoculars for Stargazing
For astronomy binoculars, Amazon has a great range to choose from including some best binocular brands. Among the brand names are Nikon, Orion, and Celestron astronomy binoculars. Here we look at two Celestron binoculars for skywatching.
Cometron 7×50 Celestron Binoculars Review
A set of beginner astronomy binoculars, 7×50, like these will give you a field of view of about 7 degrees in diameter. Compare this to a typical amateur telescope (even when using low power) with a field of view of only 1 degree. This translates to 40–50 times the area being visible with this pair of binoculars compared to the telescope.
This Celestron set is water resistant, which is what you need for outdoor use, especially at night when you are likely to experience dew or mist.
With a 50 mm objective lens, the field of view is 357 feet at 1000 yards. The lenses are multicoated with large exit pupil (7 mm). The distance between the centers of the pupils (IPD) is 56–72 mm and close focus distance, which is the closest point that the binocular can focus on, is 26.2 ft. Eye relief is 13 mm with a folding eyecup.
Housing is aluminum. Accessories include carrying case, objective and eyepiece covers, and lens cloth.
This is a Porro-prism binoculars set (objective lenses and eyepieces are offset). The prism material is BK-7.
This Celestron set comes at a price in the range seen for the best budget binoculars for astronomy.
Pros: One of the best binoculars for the price for beginners with features of a large pupil exit (best for the under 30 s), Porro-prisms, and AR coating.
Cons: Not optimum for those who need to wear glasses (i.e., those with astigmatism) given the eye relief of 13 mm and older users would be better with a pupil exit of 5–6 mm. Also, if you want a higher grade prism material, look further and consider paying more.
Get the latest price of the Celestron 7×50 Binoculars at Amazon. See details.
Celestron SkyMaster Giant 15×70 Binoculars
The field of view is 231 feet at 1000 yards or 4.4° for these binoculars Celestron make with a 70 mm objective lens and 15 magnification.
The long eye relief and soft rubber folding eyecups make this ideal for wearers of glasses and with an exit pupil of 4.66 mm, one of the best binoculars under 100 dollars for mature astronomers.
Users have claimed that galaxies, like the Andromeda, are easy to spot with these binoculars, with one noting the view of face-on spiral galaxies was better than with a 10″ telescope.
The optics are multi-coated.
This is a Porro-prism binoculars set (objective lenses and eyepieces are offset). The glass material is high index BAK-4. Close focus distance is 47.2 feet.
It comes with many accessories, like lens covers, rain guard, carrying case, neck strap, and cleaning cloth. It does not come with a tripod but can be used with a tripod.
This Celestron binoculars set is also water resistant.
Pros: Constructed with high-grade prism material, BAK-4, which is optimum, inferring better light transmission and edge-to-edge sharpness. Great for wearers of glasses given the long eye relief. Especially suited to older users with an pupil exit of 5 mm.
Cons: Doesn’t come with a tripod, though it is tripod adaptable. With an objective lens of 15, the use of a tripod is recommended.
See the latest price on the Celestron SkyMaster Giant at Amazon. See Details.
How to Use Binoculars for Astronomy
I think everyone would or should know the basics of using a pair of binoculars. There are three things that can cause you a little bit of frustration with those good astronomy binoculars. One is focussing, two is image stability, and three is finding the object.
Focusing the Binoculars
I go over the basics of focussing in How to Set Up Binoculars, further down.
Binoculars Best Ways To Steady Them
You need to keep the binoculars steady for a clear view. You can try to brace yourself by placing your elbows on a table, a railing, or the roof of your car.
One option is to buy a mount to hold the binoculars steady. If you have a camera tripod you can add a bracket that is designed to attach to it. This will be a cheaper option than buying a specific astronomy binocular tripod.
The SnapZoom Universal Binocular Tripod Mount is useful because it suits all. That is, you can use it with binoculars that don’t have that threaded tripod socket.
You can get this mount at Amazon. Check out the latest price here.
Binoculars with Image Stabilization
Image stabilized binoculars will avail of a steady experience and stunning views without the shake. These binoculars have sensors that detect movements in high or low light conditions.
The downside of these is the battery usage. And, then the price.
Finding the Object in the Night Sky
People tend to look lower than the object they wish to focus on when using their binoculars or telescope for astronomy. Practice helps with this. Try tipping the binoculars up.
Sometimes it’s easier to first find an object that stands out and then star hop across to where you want to go. I find using a tree or some other landmark as a pointer to the object and then moving your binoculars up to the object also helps.
It’s a good idea to practice on bright objects first until you get the hang of it.
It’s also best to plan your timing as it is difficult to look directly up with binoculars especially with a tripod. You might want to get comfy and lay back in a reclined seat or on a rug on the ground while hand-holding the binoculars if you are wanting to study the center of the sky.
How Do Binoculars Work?
They are optical instruments based on binocular (two-eyes) vision. Think of a set of binoculars as two telescopes put together to focus on the same point. The following is a basic overview.
The binoculars have two lens elements, one in front of the other, in each scope. The lenses capture and bend the light to give you a magnified view of what you are looking at. The first lens is the ‘objective’ lens. It captures the light from the distant object and the second lens element that sits behind it, magnifies the focussed image produced behind the first lens. So that you see the image the right way up, the binoculars have a prism (a roof or a Porro prism) inside to rotate the image.
How to Set Up Binoculars
Getting the binoculars ready for viewing can be done in less than 20 seconds.
Time needed: 1 minute.
How to set up binoculars in 3 easy steps:
- Right lens – focus binoculars
Place a lens cover over the right lens (or close that eye) and focus the binoculars.
- Left lens – adjust eyepiece
Switch to left side. With left lens covered (or eye shut), adjust the eyepiece ring until the image is sharp.
- Ready to go
Remove the lens cover or open your eyes and you are ready to go
How to choose binoculars?
For the best binoculars for astronomy, look for these features:
- A complex anti-reflection coating
- Porro prism – if you want better bang for the buck
- A high-grade glass, such as BAK-4, in the prism system
- The precision of the lens shape
- Consider at least a 7x magnification and 50x objective lens diameter
In the end, what you buy in binoculars will depend on your budget. How much do you want to (or can afford to) spend? And, do the binoculars have the features to satisfy you for use of the binoculars astronomical wise?
Other features to consider:
- Zoom or in built camera or not (recommended to avoid)
- Exit pupil (age-related)
- Eye relief (especially if you wear glasses)
How to Buy Binoculars?
Where to buy binoculars for stargazing? You can buy binoculars online. Some of the best cheap binoculars for astronomy can be found at Amazon.
Nikon: Types of Binoculars |
Information was also gathered from owners of astronomy binoculars and binocular reviews and publications:
- The Editors of One-Minute Astronomer. 2009. Stargazing for Beginners. A Binocular Tour of the Night Sky (v1.5). Mintaka Publishing.
- English, Neil. 2014. Grab ‘n’ Go Astronomy. The Patrick Moore Practical Astronomy Series. Springer.