How To Choose Binoculars For Astronomy & Stargazing (Best UK Guide)
Checking the night skies for star constellations, planets, asteroids, or any other astral phenomenon is a great way to spend a warm Summer evening. To get an enhanced view of the heavens, a decent pair of binoculars is essential. Your brain collates all of the information that your eyes collect. Things like colour, light, and the opposites like dark and light.
By using binoculars you will be able to see 25 to 50 times more stars than it’s possible to see with the naked eye, depending which pair of binoculars you choose. This isn’t just due to the magnification of the lenses, it’s also due to perceptual narrowing of the flow of information entering your brain. Some people dismiss this phenomenon, but it is a measurable effect.
What’s Best Binoculars Or Telescopes?
Even small telescopes are big, this makes them heavy and hard to maneuver. Plus they need to be placed on tripods for stability. We all shake slightly when holding heavy objects and this is more apparent when looking through a telescope.
Telescopes For Astronomy
Telescopes do magnify objects but their main objective is to gather light, but what actually happens is the more a telescope magnifies an object, the dimmer that object appears to be.
That is a serious issue when viewing deep space objects. All objects in space apart from the moon which can sometimes appear to be too bright, and the odd planet when it’s close enough, will be too dim to see through the small lens area of a telescope. Then there’s the issue with the field of view, telescopes have a small field of view. That means you might spot something with your eye, but once you lift the telescope to your eyes you’ve lost it. Other issues with telescopes is the image they produce is upside down, and many show the object backwards because of the mirrors used to produce the image.
Binoculars For Astronomy
Binoculars, even cheap ones, can be pressed against the eyes while holding close with both hands, this keeps the images fairly still. As binoculars have two lenses (one for each eye) you get twice the chance of painting the image onto your brain. As it’s your brain that collates the images you see through your eyes, two is better than one.
Binoculars have a wider field of view which allows you to scan the skies easier. Plus binoculars allow you to appreciate the objects’ relationship with each other. Like star constellations and planetary alignment.
Which Binoculars Are Best For Stargazing?
Now that we have established that binoculars make more sense than telescopes (unless you can gain access to an observatory), we now need to work out which pair are best for astronomy and stargazing. So let’s start with some basics.
The Field Of View
The field of view is shown in one of two ways on binoculars. It will either have printed on it something like 315 feet at 1000 yards or 6 degrees – they’re both the same. Basically the higher the number the greater the field of view is. Incidentally the disk of the full moon is around half a degree wide and your clenched fist held out at arms length towards the sky covers about ten degrees.
What Do The Numbers On Binoculars Mean?
We’re talking now about the numbers stamped onto the actual binoculars separated by an X. Something like 25×70, this gives us the rate of magnification and the objective lens size. In this case a magnification of 25 times (the x symbolises times) with an objective lens of 70 mm. So an object will appear 25 times larger through the binoculars than it would with the naked eye.
The objective lens is the lens nearest to the object you’re looking at (the smaller lens is called the ocular lens, ocular – to do with the eye). The bigger the objective lens is, the more light it allows into the binoculars so the brighter the image appears.
What Binoculars Are Best For Stargazing?
There are some extremely large sized binoculars available and it’s tempting to go for something massive to see more through. But it doesn’t really work like that. In reality the larger they are, (and by larger we mean the objective lens size) the heavier they are. If they are too heavy you’re less likely to carry them around too much and therefore far less likely to use them. The reality is in many instances, smaller is better.
A pair of 8 x 35 binoculars are great for watching birds and they will be small enough to remain still while you’re looking at the stars in the night sky. Having a wide field of view is usually a bonus of lower powered binoculars. Too high magnification can cause some problems when looking at the night sky.
Take meteor showers for example, if you are using too high magnification you could dazzle your eyes if you look directly at one of those incredibly bright fireballs, which will make it difficult to see others or smaller objects for some time afterwards. So it pays to give some serious thought to the size and magnification of your binoculars. We recommend a 10×50 pair of binoculars as a good starting point.
Is Waterproofing Necessary For Stargazing Binoculars?
This is really largely dependent on when, where and how you intend to use your binoculars but one thing that’s certain is moisture. This planet is roughly 71% water, and rain is a fact of life, especially when you least expect it. Having a waterproof pair of binoculars makes sense in our opinion. There are various levels of waterproofing and in an attempt to combat fraudulent claims, the industry has come up with its own coding for expected degrees of waterproofing.
What Level Of Waterproofing Is Best?
Without boring you with the technicalities of the waterproofing coding system, let’s just say that the higher the IPX value the better the level of waterproofing is going to be. In our opinion IPX6 and above will be perfect for any weather conditions the UK can throw at you.
Along with waterproofing, having fog proof binoculars gives you complete cover from not only water, but dust and debris too. That’s because to make the binoculars fog proof they have to purge them of oxygen and fill them with an inert gas like argon or nitrogen. As these gases contain no moisture content they cannot react with temperature variations and so do not fog up when coming from hot rooms to cold gardens etc.
Once the gas is sealed in, none can leave the lens tubes and as an added bonus nothing can enter either. This means no dust, debris or mould spores that often caused problems for our ancestors with their telescopes and binoculars.
What Is Exit Pupil And Is It Important?
The exit pupil is the size of the bright discs you see in the eyepieces (ocular lens) when holding them at arm’s length. The exit pupil should be larger than the size of your pupils in the dark. Most people have an exit pupil of 7mm but it decreases by around 1 mm every decade past 30, so at 40 your exit pupil should be 6mm and so on. It’s important to get this right because the only light that passes through the binoculars can exit them and pass through your eyes. So the larger the exit pupil, the more light that can be transmitted to your eye.
Can The Binoculars Be Fitted To A Tripod?
If you manage to find an interesting object somewhere in the extremities of the universe and you’d like to show it to a family member or a friend, wouldn’t it be nice to leave the binoculars set up while you go and find them? Well with the binoculars set up on a tripod that’s entirely possible. If this is something you’re likely to want, then you need to check for a screw mount point on the binoculars. Or you can get a binocular tripod mount that screws into the tripod and your binoculars rest on top of the mount.
Don’t just assume that any old camera tripod will do the job either, because in most cases they will only work up to around 30 degrees above the horizon. That means you’ll be missing out on more than two-thirds of the night sky which is not ideal. You can get specially designed rigs just for stargazing with binoculars, the problem is some of the more involved designs can cost more than the binoculars.
What Type Of Binoculars Are Best For Astronomy?
There are two main types of binoculars available for stargazers, bird watchers or anyone else who wants to see far away objects up close. They are;
- Roof Prism Binoculars
Roof prism binoculars look like two straight tubes divided and joined by a central focusing ring. They are relatively lightweight and compact by design. It’s all to do with the way the prisms are fitted to the lens tubes that keep these roof prism binoculars so compact.
What’s not so small though, is the price. To get a decent pair with the prisms fully coated (which is necessary to avoid the image from phasing slightly out of focus) will cost considerably more than a Porro prism pair of similar quality. But they are so much easier to carry around and as they weigh so much less they are easy to hold up to your eyes for longer periods of time.
- Porro Prism Binoculars
These are the more traditional style of binoculars, with fairly narrow eyepieces spreading out to bulging centerpieces (which is where the multi-prism set up is housed) and then on to the even wider objective lens. This type of binoculars have been around since the 1850s and the design is ultimately the same now as it was back then. The only problem with Porro prism binoculars is the internal set up is liable to get knocked out of alignment with fairly slight impacts.
If the prisms do get knocked out of alignment you will experience eye strain, headaches and possibly migraines. If you are a slightly clumsy person, then it might be a good idea to invest in roof prism binoculars as they are more robust.
Is Image Stabilisation Necessary For Stargazing Binoculars?
The fact is we all shake when holding any object for a long while. It’s also true that under normal circumstances we don’t notice the slight shake. But looking through binoculars will highlight that shake especially with a magnification above 10x. If you decide to go for a higher magnification, then you should consider a pair with image stabilisers.
They will be more expensive and the batteries will need replacing regularly. Plus having onboard image stabilisers will increase the overall weight of the binoculars.
What Can You Expect To See Through Binoculars In The Night Sky?
Once you decide on the best binoculars for you, you can expect to see some pretty amazing images in the night skies. Did you know that on a clear night away from any light pollution, just with the naked eye you can see at least 3000 stars. Look through a pair of binoculars with a low magnification and lens size, say, 7×35 and that number increases to approximately 1000,000 stars.
Looking At The Moon Through Binoculars
The first stop on your skyward tour has to be the moon. You will not believe just how much detail you can see through a pair of hand held binoculars. There are craters like the one visible at the bottom of the moon which is called Tycho, which is easy to identify because of the white rays that spread out from the crater and are even visible from the reflective light of Earth.
Even when the moon is not full, you will still be able to see all of its face through binoculars, by the reflective light from Earth. There are also mountain ranges, “seas” and many craters to explore.
Planets Of The Solar System
Once you’ve had your fill of the moon, you can look further afield and try to identify some of the planets as they drift across the night sky. The easiest planets to identify are Saturn and Jupiter and they can be seen quite clearly with the naked eye.As the brightest two planets travelling along regular paths, they have been studied for many centuries.
This is the largest planet in the solar system and it should be easy to identify with binoculars. You should also be able to spot at least four of Jupiters’ moons orbiting around its bulky mass. Look for four pinpricks of light circling Jupiter. They will be Ganymede, Europa, Io and Callisto. It’s possible to see Jupiter even before night comes, it’s often visible just before dusk.
As the second largest planet in the solar system, Saturn is relatively easy to spot with binoculars too. Through reasonably magnified lenses it should show out as a bright oval shaped object. With higher magnification it’s possible to make out the rings and possibly one of its moons -Titan.
Venus is the second closest planet to the sun in our solar system and it really reflects the light from the sun. It’s best to look for Venus at twilight before the sky becomes too dark.
They call Mars the red planet, and it really does look red, especially seen through a pair of binoculars on a cloudless night.
As long as you are looking in the right direction it’s relatively easy to spot Uranus through binoculars. It often appears to have a greenish tinge, this is due to its atmosphere containing methane.
The Milky Way
It is possible to get a glimpse of the milky way through binoculars but you will need to be in an area with no light pollution. Sadly you will not experience the full colours of the milky way because of the distance but you will see it through shades of grey.
There are many constellations visible in the night sky depending on where and when you are looking for them. Check online for the various phases of planets and constellations to get yourself orientated. A good place to start is In the sky.org  where you can set your location and an interactive map shows all the constellations that should be visible in the night sky.
What To Avoid When Buying Binoculars For Astronomy
There are as many gimmicks as there seem to be binoculars, some of them can be quite useful (like image stabilisers) and some are best to steer clear of. For instance in our opinion you shouldn’t bother with zoom lenses on binoculars, at least not for stargazing. Good zoom lenses require a high level of precision to get them right, and that precision comes at a price. So if they seem too good to be true then they probably are too good to be true. Another new innovation are binoculars with cameras built in, these might work OK during daylight, but at night they fail miserably.
4 Ways To Avoid Shaky Images Without Using A Tripod
As we get tired, our arms begin to shake, only slightly, but at 10x or 15x magnification that shake is magnified by 10 or 15 times. So it is going to be necessary to find some way to control this shake somehow if you want any chance of seeing anything in the night sky. You can;
- Lean Against A Strong Object
If you’re standing up, try leaning against a tree, wall, fence or a car or anything that will take your weight but give you some support. This should help you to steady your image.
- Try Sitting In A Reclining Chair
One that leans right back to almost horizontal. This will allow the chair to support you, and the weight of the binoculars should press them into your face making less room available for the shakes.
- Use Lower Powered Binoculars
As we said earlier, with higher magnification comes more exaggerated movements. Plus higher objective lens sizes means more weight for the glass lens, which is of course right at the far end of your point of support.
- Tuck Your Elbows In To Your Ribs
By tucking your elbows in you will allow your body to take most of the weight, this works better in conjunction with the leaning against an object method (#1).
Frequently Asked Questions
For astronomy, the best magnification is anywhere between 7x and 10x.
The strength binoculars you need for stargazing is nothing stronger than 10x magnification and nothing larger than a 50 mm objective lens. This gives you 10 times magnification and allows enough light in to see clear, bright images.
10×50 is the perfect binocular size for astronomy.
You can look at stars with binoculars. We would suggest no greater magnification than 10x and no greater objective lens size than 50 mm.