Binoculars can open your eyes to many sights and satisfy many curiosities. They can also be complicated and confusing when you first start looking into buying a pair.

The decision on what binocular to buy can be very difficult when presented with the large array of possible choices.

We will try and answer those commonly asked questions to give you the best possible advice, so you can find binoculars that really do fit your needs.

Types of binoculars

Theater binoculars or Opera Glasses

these are the ones that can be anywhere from tiny to small. 3x25 is a common size for opera glasses. I have a pair of vixen 12 x 25 binoculars that work well for theater glasses and also for small binoculars to carry in the car. They make some very sophisticated binoculars for theater glasses ..where the emphasis is on the size of the binoculars more than other considerations.

Mid size binoculars....

At least that's what I call them. I consider most bino's with objectives in the 30 to 50 range with the 8 through 12 magnification etc....in the mid bino range. these are the 8 x 25, 10 x 50 binoculars that are a great set of glasses for almost anything. I personally believe everybody should have a pair of 10 x 50 binoculars! This is the best all around set of binoculars. They are great for land, sea and sky!

Large or astronomy type of binos ..

These are the large optic glasses with objectives in the 60 through 120 millimeter range ..Large optics allow more light so that is a must for astronomy. Depending on how much detail you want to see will determine what the best magnification will be for you. The higher the magnification the more narrow the view. Also higher magnification makes a set of large binoculars nearly impossible to hold still unaided. That means if you get a set of large binoculars plan on picking up a tripod or parallegram to hang them on. For a large set of binoculars I really like the 20 x 100 combination. That is a lot of aperture, they can be hand held if needed and they have a good exit pupil of 5mm.

What do the numbers on binoculars mean?

The numbers tell you the configuration of a binocular. Let's take 10x50 binoculars for example. The first number (10) refers to the magnification, or, how many times closer an object will appear when looking through the binocular compared to looking through eyes only. The second number (50) indicates the diameter of the objective lens (the light-gathering lens) of the binocular.The MM stands for Millimeters.

Remember, There is about 25mm to the inch

Note: The diameter of the objective lens is directly related to the size of the binocular -- the larger the objective lens, the larger (and often brighter) the binocular

For compactness you may want to look at glasses with a 'roof' style prism as apposed to the porro prism.

What is the difference between Porro prism binoculars and roof prism binoculars?

Porro Prism Binoculars;

Binoculars with porro prisms provide a bit better optics for the money. They are the oldest tried and true design. They are a little more prone for damage being a little less protected than the roof prism design.

Reversed Porro Prism Binoculars

Reversed porro prisms style binoculars are usually very compact and fit the hand and in the glove box of the car etc.

Roof Prism Binoculars

These are the type of binoculars you see that have the straight barrels. They actually look like two telescopes side by side. There is no bulges where the prisms are placed as they are on the 'roof' of the scope barrel. Thus they make the binoculars less bulky...The roof prism binocular is typically more expensive than the porro prism type with the same capabilities.

How much magnification?

Just like a telescope, the first question you want to ask yourself is what it is you want to do with your binoculars.

You will want a binocular that will mach your lifestyle or hobby. So, think about the demands of your hobby before you select a pair of binoculars. If you plan on using your binoculars for birding or sports, maybe just having a pair in the truck or camper you can snatch up real quick to look at something interesting? You will want a pair of binoculars that are compact. Plus with a lower magnification and mid size objective lens. Some where around a 8 x 40 or 10 x 50 are great for mid size binoculars.

The lower magnification makes it easier to hold the binoculars still for ease of viewing. High magnification binoculars are hard to hold still and may require you to rest them on a stable support or us a tripod.

Wider FOV (field of view) is better for following moving objects such as birds or sporting events. Wider FOV comes with the either lower magnification or larger objective or both. More on that later in what is FOV.

Exit pupil

Exit pupil is the size of the outlet for the light being emitted out the eyepiece of your binoculars. It is also the size of the iris of your eye which is smaller in the light and gets larger in the dark ...known as night vision by astro folk.

If you divide the objective size of the glasses by the size of the magnification will give you the exit pupil for your binoculars. In the case of the 20 x 100 that is a 5mm exit pupil. Right around what most human eyes are when adapted to dark surroundings.

Field of view or FOV

Just what is FOV? It is the how wide of a view you get through an ocular device. I put it in this context because FOV is the same in all scopes big, little, single or double. FOV is determined by the size of the objective opening and the amount of FOV in the eyepiece. A more complex EP(eyepiece) can allow a greater area to be seen. The simple EP will give you around 390 ft at 1000 yards, a better EP may give you more like 496 ft at a 1000 yards. Just remember that the larger field of views will show fuzzy out around the edges.

If you are using binoculars for astronomy you cant really measure the FOV at a thousand yards. So the FOV gets converted to degrees of angle. So the 390 ft at a 1000 yards equates to 7 degrees for the true field angle. with the magnification of 7 degrees, the FOV appears to be 50 degrees or apparent field of view. The better EP would give an apparent FOV of 65 degrees. You can see the eyepiece is instrumental in determining the FOV. This is why the combination of ep and aperture is important to consider when looking for good binoculars.

Remember the higher the magnification of the glasses the more narrow the FOV but the detail is better.

We are starting to see that the binocular has magnification, aperture, exit pupil, true FOV and apparent FOV all related mathematically Change one and the others are affected.

How about the objective

The objective lens is the front lens of the binoculars. The 'big' end if you will. It is the aperture or diameter of the objective that is the biggest limiting factor of how far, how wide and how faint of object you will get to see. The amount of light photons you gather is the name of the game...in astronomy the bigger the opening the better. For things like birding and sports it is not nearly as important. Make sure you read how the objective and eyepiece affect the operation of the binoculars.

How much should I spend on binoculars?

This is a loaded question...and my answer is usually something like ...how much can you spend? or What do you want to do with them?

Like anything of quality you want to get the best you can for the money you can afford..you want the best binoculars for the money...

I suggest you do as much research as possible before you buy..

Remember the best binoculars are the ones that you will use! If they hurt your eyes or you can close them or open them enough to fit your face, If you cant use them with your glassed on ...etc. They are not good binoculars! Do your research and get the best binoculars for YOU. Then you will know how much to spend...

How important is the glass used in binoculars?

This question gets us back to quality ...usually the difference in price of binoculars is the glass and coatings.

The glass and the grind of the optics is everything! It is the grind (shape) of the lens and the type of glass used that controls how the light is adapted or guided to the focal point in the scope. There is about five billion trillion pages of info on light refraction and wave lengths of colors and how they react coming through glass and another billion pages on the math involved.

All I know is the better the lens guides the light and the colors coming though it the better the view through the binoculars and the easier it is on your eyes...No headaches etc.

That is why you read about types of glass like ED (extra low dispersion) and HD (high definition) glass.hese types of glass provide highly resolved images and keep the colors real buy controlling how the different wave lengths are brought to the focal point behind the lens. It is worth the money for quality glass in your binoculars...

Along with good glass there is the question of coatings. Good coatings are not a scam! They will enhance the light transmission in your binoculars with anti reflection and other filters on the more complex coatings.

The cheaper binoculars don't employ the best in coatings...nuff said.

What if I wear eyeglasses while using my binoculars?

With quality binoculars this is not usually a problem. I find it is better to wear my glasses if I am sharing my binoculars that way the next person don't have to re adjust the focus.

Look for binoculars that have at least a 15mm eye relief. That is how far the image is projected from the lens to the focal point. This can vary anywhere from 5mm to 23mm check the eye relief when you do your research for your binoculars. If you plan on sharing your bino's like at star parties etc. then get a pair of binos with a long eye relief, they are more adaptive and easier to use.

If you wear glasses and the eye relief is to small you will not be able to see the complete FOV

Binocular Eyecups

These are really cool things on the eyepiece that shade your eye from outside light and help keep you at the proper eye relief. They will be rubber that folds up or a EP sheild that twists or pulls up. USE THEM.

Do my binoculars need to be waterproof?

Water proofed binoculars is an added expense you really only need if you use them in a really wet environment. Are you on a boat most of the time? Water proof....

Are you in the snow or rain a lot? water proof...

Live in the desert? okay you get it....

water proof binoculars are purged with nitrogen and sealed The beauty of WP binos is that the manufacturers warranty covers them if they get wet and fog up etc..

How do I properly focus my binoculars?

This is how you set the diopter adjustment of your binoculars. you know how good binoculars have the right hand eyepiece so it is adjustable? This is a diopter adjuster. It allows you to set your binoculars to fit the differences of your particular vision idiosyncrasies.

Using the center focus, you want to adjust the binoculars with your right eye closed to a focused position. Then close the left eye. With the right eye open adjust the right eye till the complete view comes into focus and sharp. This is the setting that works best for you. Now you just use the center focus when you need to adjust the binoculars. If you share your binoculars and someone changes the diopter adjustment you will have to re adjust it for you again.

It is this adjustment that will allow you to use your binoculars without your eye glasses if you are more comfortable with out them. Or you are viewing for a long period of time.

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