Astronomical Binoculars

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>Binoculars for Astronomy

Anyone with an interest in Astronomy should own a good pair of binoculars. Even avid amateurs with a houseful of telescopes will have at least one pair of binoculars at the ready.

It was only fairly recently, during my training into becoming a field guide (safari guide) that I learnt in any detail some of the southern hemisphere's star constellations, it was also the first time that I had ever really looked at the stars through binoculars. Even though I was only using my Steiner 10.5x28 Wildlife Pro's which are far more suited to looking at wildlife than the stars, I was amazed at just how many more stars you can see through binoculars than you can with the naked eye, so much so that it became difficult to pick out the constellations because of all the "new" stars that I could now see.

If your main interest in astronomy is exploring the fine details on planets or showing structure in distant galaxies, you will probably also eventually want to get a telescope as binoculars just don't have enough magnification. However, if are new to astronomy or if you thrive on large open star clusters and big, extended nebulae, binoculars can actually work better for you than a telescope. It is often said that binoculars are the best "first telescopes" you can buy and even an experienced astronomer usually keeps one with them at all times.

>Binoculars vs Telescopes

The video below is of Bill Burgess, the owner and founder of Burgess Optical, world-renowned for its custom-built telescopes and planetary eyepieces describing why a set of binoculars may be best option for you especially when starting out in astronomy.

>Recommended Binoculars for Astronomy

What pair of binoculars that you should get, will depend on how specialised and exactly what you want to use them for: The best binoculars for someone who wants to observe the stars with, but also then use during the day will be different to those that want to only use the binoculars for star gazing and don't have to worry about carrying them about.

>Magnification

The ideal magnification on a set of binoculars to be used for astronomy will differ depending on the way you intend to use it:

Hand held binoculars for astronomy and other general use
Hand holding a binocular is an enjoyable and less expensive way to enjoy astronomy, many of these binoculars are cheaper than the larger ones and there are no accessories to buy and there is no set up time. They also have the added bonus in that they are far more versatile and you can use them for many other applications. If you plan to use this method, you should keep magnification below 12x in order to maintain steadiness. A good pair of binoculars with a magnification of 7x to 12x and a large objective lens will show you hundreds of star clusters, nebulae and even some galaxies.

Large binoculars to be used on a tripod
Putting a binocular on a tripod or mount pushes the binocular into the telescope realm as far as operation goes, but it is the only way to handle magnifications over 15-20x effectively. An astronomy binocular of 15x to 30x will show more detail and resolve more stars, though it still won't turn your binocular into a telescope for observing planets. Still, there is nothing like the view in a 25x100mm binocular to take your breath away on a dark, clear night. (importance 7/10)

>Objective Lens Size

This is the size of the large lens at the end of your binoculars, it is indicated in the name of the binoculars and is measured in millimeters. so for example the Celestron 25x100 Astronomy Binoculars have an objective lens diameter of 100mm. The larger the objective lens, the more light your binoculars let in, this is very important for low light conditions and so extreamly important in astronomical binoculars.

Obviously the larger the lenses, the larger the binoculars, so again the size of your objective lenses are important depending on what you wish to use your binoculars for. Hand held binoculars have to be light enough to hold up to the sky, whilst binoculars mounted on a tripod can get very large.

Hand Held Astronomy Binoculars
If you are going to use your binoculars for astronomy and don't want the hastle of using a tripod, 7x50 binoculars are a classic size. In recent years the giant binoculars have captured the headlines, but these are still unbeatable for viewing really extended open clusters and nebulae and as far as astronomy binoculars go, nothing is easier to use tha a 7x50.

Giant Binoculars
Binoculars with objectives of 60mm or more are called giant binoculars, but it is possible to hand hold a 10x70 or even an 11x80 for short periods of time by grasping them around the barrels near the objectives. Larger objective lenses will reveal fainter stars and probably more detail, but will become too heavy to steadily hold up to your eyes for any length of time.

A increased magnification of 10x70 or 11x80 will add a little more detail to what you can see in a 7x50 and maintain the same image brightness as well. So as far as hand held binoculars go 10x70 or 11x80 represent the upper limit of what is practical for hand holding, but for extended use you may wish to use a tripod anyway.

Binoculars with magnifications over 15x and objectives of 80mm or more can rival and exceed the view of some small telescopes for certain types of objects and you get the comfort of using two eyes. The one downside to most giant binoculars is their fixed magnification, though a few models are now available that offer interchangeable eyepieces. (importance 7/10)

>Exit Pupil

However this is not the whole story, the size of the objective lens determines how much light can enter the binoculars, it does not determine how much light enters your eyes, which is far more important. This measurement is known as the Exit Pupil and to determine this you divide the Objective Lens size by the Magnification of the binoculars.

Any binoculars with an exit pupil under 5 are only really suitable for day time use. Any with 5 or more can be used for astronomy and so this is an important measurement to check when deciding on which pair of binoculars to purchase. (importance 9/10)

>Tripods

Any pair of binoculars to be used for astronomy with a magnification of more than 10x or 12x and or with objective lenses of 70mm or more will need a mount of some type. The larger and heavier the binoculars, the larger and stronger the mount that you need.

Most large heavy duty camera or video tripods will work for 80mm and some 100mm binoculars. Be sure to compare the weight of the binocular with the maximum load capacity of the tripod, if listed. Unfortunately, this figure is not standardized, nor will it guarantee how well it will work with a large binocular, but it is a place to start.

For 80mm binoculars, look for a tripod that lists a capacity of at least 12lb and 15lb or more is better. Another thing to check is the actual weight of the tripod, light tripods will struggle when loaded with a binocular of equal weight or more. Generally because portabilty is rarely an issue when it comes to tripods for astronomical binoculars, bigger is better. Quick release plates are a convenient feature, to look for, but check to see if they fit very tightly, if they fit loosely in the tripod head, you will get some unwanted sag.

>Type of Focus

You find good astronomy binoculars with either individual eyepiece focus (fixed focus) or center focus.

Fixed Focus Binoculars
Individual eyepiece focus is a practical system since there is little in the way of focusing when using a binocular for astronomy. Once you have set the binoculars to your eyesight they do not need to be focused again, these are sometimes confusingly known as self focusing or auto focus binoculars. This system works well when looking at objects from medium to far distances away. They have far less moving parts than center focus binoculars making them much easier to seal against dust and moisture.

Center focus Binoculars
The center focus binocular is easier to use when there is a need to refocus a lot, for example if you are sharing a binocular with others and so are far more versatile than fixed focus binoculars, important if you plan to use your binocular for applications other than astronomy.
(importance 4/10)

>Price of Binoculars

In the past a quality giant binocular would be a very expensive purchase, but there have recently been many more manufacturers producing astronomy binoculars, many of which are made in China, which has brough the prices down.

What is good is that many of the new Chinese optics are made to very high optical standards. Some popular brands include the Oberwerk which have plenty of nice features including collimation screws, Celestrons, Meades and the excellent Apogee brand of binoculars. All of these offer fantastic quality for the price and bring giant binoculars within reach of most peoples budgets. (Take a look at this review on Cheap Binoculars for Astronomy)

Generally you should be able to find a quality set of 80mm binoculars for around $100 to $300, with 100mm models starting at about $400. High end models can cost over $1000 that come with interchangeable eyepieces and pier mounting options.

The best giant binoculars for astronomy are not chap and are still made in Japan. The best brands include Fujinon who produce everything from a 70mm binocular to pier mounted telescopes. Kowa observation binos and the superb Nikon Astronomy line are considered to be some of the finest binos of their type.

>Close Focus

This is obviously only important if you plan to use your binoculars for other uses besides astronomy and most giant binoculars have a poor close focus range. (importance 2/10)

>Waterproof Bins

There is not much of a need for an astronomy binocular to be waterproof, water resistant is enough as using them at night can expose a binocular to dew and moisture, which can cause a non-waterproof model to mist up inside the mechanism. (importance 2/10)

>Field of view

The field of view on astronomy binoculars is not as important as it is for people using their binoculars to view unpredictable, fast moving objects, like birds, but it is still fairly important. Field of view is basically the width of the scene that is in view when you look through your binoculars, for a full explanation see field of view in my optics glossary. A wide field of view will make it easier to find objects when looking through the binoculars.

Everyone talks about magnifications and there is no doubt that high magnifications yield beautiful views of the Moon, planets and fine detail in some deep sky objects. However, many objects in the sky are too large to fit into the field of view of a high power eyepiece. These objects demand a wide field of view to appreciate their beauty and delicate form.

Binoculars with as wide a field as possible might seem best, but you can go too far and wide field of view binoculars may exhibit distorted or out-of-focus star images at the edges of the field. In simple terms lower magnification often means wider field of view. So what you are looking for is the wider field of view as possible in your chosen magnification. For more take a look at this article on Wide Angle Binoculars. (importance 3/10)

>Eye Relief

Eye relief on a set of binoculars is very important if you use glasses. Take a look at Eye Relief in my glossary for a detailed explanation, but basically it is the distance behind the ocular lenses where the image is in focus. So if you wear glasses, you can't get your eyes as close to the lenses, you need a longer eye relief that basically projects the image beyond the ocular lens on the binoculars. So if you wear glasses, you should be looking for an eye relief of around 15mm, to see the full image full image. The down side to long eye relief is that it usually reduces the field of view. Some people wonder if you need to wear glasses at all using binoculars, well If you are near-sighted or far-sighted, you can use your binoculars without wearing glasses and the binoculars focus will compensate, but if you have astigmatism, you will need to use your glasses.

Eye-cups are related to the eye relief as they keep the distance from the oculars to our eyes, but also help keep stray light away from your eyes while using binoculars. Many eye-cups are made from rubber and can roll up or down depending on whether you use lasses or not. The problem with these is that the constant rolling causes the eye-cups to break. Another type are eye-cups that slide rather than roll, but these can be hard to keep in place. The third type are eye-cups that twist up and down and so they can be left at any position from all the way up to all the way down, some even have click stops at regular intervals with the eye relief distance for each stop marked on the cup so you can get the perfect eye relief for your vision. (importance 8/10 if you uses glasses not hugely important if you don't)

View >> All Astronomy Binoculars in the Best Binoculars aStore.
Below are some binoculars that I recommend as great astronomical binoculars.

View >> All Astronomy Binoculars in the Best Binoculars aStore.

View >> All Astronomical Binoculars reviewed by Best Binoculars & Reviews.

Below are some books on astronomy specifically for people using binoculars instead of telescopes.

View >> All Astronomy Books for Binoculars in the Best Binoculars aStore.