How to Choose Marine Binoculars

Binoculars are an incredibly important tool to have aboard your boat. And today we're going to look at some different binoculars and try and find out just what features and facts you should bear in mind when you're choosing a new pair.

First off, a couple important features. All marine binoculars should be filled with an inner gas - nitrogen, argon, something like that so that they don't fog up inside when they go through a very drastic temperature change, which can just be walking from the cabin to out on deck. It's very important. Secondly, obviously since we're talking about marine binoculars, they need to be waterproof. There are two numbers you need to be aware of that go a long way in helping you understand a pair of binoculars. This right here is 7 by 50. The 7 stands for how many times the binoculars magnify. The 50 stands for the objective lens diameter, and this tells you basically how large the lenses are. Larger is generally thought of as better because it lets in more light. Standard marine binoculars like these are commonly 7 by somewhere between 30 to 50.
Now, here's why it's important to stay with marine binoculars. I have another binoculars and it’s not marine. These are just regular binoculars. These are 10 times magnification, so they're even stronger than this pair, right? But they're 10 by 20s. When I hold these up and look through them, there is so much motion that on a boat, it'd be hopeless to ever try and focus in on anything.
Now, binoculars like these, you can get a couple, few hundred dollars. If you can spend a little bit more, you can get a pair with gyroscopic stabilization. Now these cost about a thousand dollars, but the gyroscopic stabilization allows you to use a much stronger magnification. These here are 14 times, and that gyroscopic ability takes the motion out of being on the boat. You can even tell the difference with your hand jitters standing here like this. For instance, if I look, there's some movement there. But when I hit the gyroscope, that's pretty intense.

The down side to the gyrobinocs, plain and simple, is cost. Now, there are a couple other considerations to keep in mind. Some people like binoculars that have compasses built in, that can be helpful. Some have range finders. And don't forget to consider weight. Really heavy binoculars do get tiring after hours and hours on the boat. There are a few other details you may want to research depending on how in-depth you want to get as you're looking at your binoculars. Things like different lens coatings, etc. But we've covered the important points here. We've covered the big items. Which binoculars are right for you? Well, that's a decision that only you can make.

There are a few things that are more fun and more important to have on board a boat than a pair of good binoculars. But it can be a little intimidating to go into a store and see the wide range of binoculars that are available. So let's take a look at some of the features that differentiates one set of binoculars from another.

Waterproof (Water-Resistant) Feature

The first thing is that marine binoculars are different than normal sports binoculars because they're inevitably waterproof or at least highly water-resistant. And this includes being filled with dry nitrogen to prevent them from fogging up inside. If you've ever picked up an old pair of binoculars and look through and see it sort of drips on the inside of the lenses that's because water can condense inside. So the binoculars that are used in the marine industry are filled with dry nitrogen gas so that they don't fog up.

Rubber Coating

Another important difference is that most marine binoculars have a rubber coating on the outside. This does two things - one is that it keeps them from sliding around as the boats in motion and the other thing is that just protects the binoculars against hard bumps, of course any binocular is better off when you don't drop it or subject it to too much motion.

Binocular’s Magnification

So one of the key features of a binocular is the magnification. Normally, when you're on a boat, you can hold steady up to about a 7 power binocular. If you get over 7 power just the motion of the boat and the motion of your body and your hands mix the view to unsteady. So you'll find most marine binoculars have seven power magnification. If you're going to sporting events something like the Lake Champlain binoculars have ten power and so this gives you it magnifies more brings objects closer but again that's because you're sitting in the bleachers of a stadium or someplace and not on a moving boat. So smaller binoculars with greater magnification although they're handy are generally restricted to land use.

Stabilized Binoculars

One exception to that rule is if you're using stabilized binoculars. They have a gyroscopic stabilization inside which takes out the movement of the boat and the movement of your hand and stabilizes the image. So in this case, these are 12 power binoculars, so with 12 power it gives you very good close-up views that a very steady view at the same time. So for most uses we'll use 7 power on land, we can usually use 10 power, or so, and if you have stabilized binoculars you can go 12 or 15 power.

Objective Lens Diameter

The second thing that you want to look for in marine binoculars is the objective lens diameter. By the objective lens we're talking about the large lens on the part that's away from your face. So for example binoculars have a 42 millimeter objective lens, so the distance from one side of the other is 42 millimeter. The most common size in marine binoculars is 50 millimeters. Now there's a reason for this. The greater the objective lens diameter the more light it lets in. now in brightly lit conditions that's not that big a deal because when you're in daytime you don't actually need the full light gathering ability of a 50 millimeter lens, but as you get darker and darker and darker either at dawn or a dusk or in the middle of the night, having the greater light gathering ability of a larger lens is a really good feature. The reason these are 50 millimeters is because this is a 7 power binocular. If you take the objective lens diameter and divide it by the power, it determines what's called the exit pupil, which is the little disc of light that you see when you hold binoculars at arm's length. The exit pupil for a 7 by 50 pair of binoculars is 7 millimeters well that's the same size as your eye when it's dilated. So if you had bigger lenses or lower power and combination you actually couldn't utilize the light because you couldn't get it into your eye to see. So we find that a 7 by 50 binocular is the normal ratio.

Focusing

the next feature to look for is focusing. All binoculars need to be focused for two different reasons. One is the difference in the prescription between your right eye and your left eye and the other is to make an adjustment for the distance at which you're viewing. So there are two distinct types of focusing. The old style of focusing uses an independently adjusted eyepiece for each eye. Now with center focus you still can adjust the left and right differences. This is how it works. I would look at an object to say across the way say a couple of hundred feet away. And one of these eyepieces is adjustable and the other is fixed. so I would adjust the center focus for the eye that is on the fixed eyepiece and then I would close that eye and adjust the other one using the adjustment the diopter adjustment. In the end what that does is it corrects the binoculars for your left right vision differences and then from then on you just use the center adjuster so it's much much easier. It used to be that to get waterproof binoculars you couldn't get them and have them be center focus now virtually all binoculars are center focus and it's a really really good feature to look. For there are two normal styles of the prisms that are in the binocular. These are called roof prism binoculars. Roof prism binoculars have sort of stacked pieces of glass inside of them and so they have a classic sort of tubular look, the light path doesn't go around angles or at least you can't determine that it does. And the advantage is that you get something that's very compact and fits in your hands. So many many outdoor binoculars and sporting events binoculars will be a roof prism style.

Porro Prism Binoculars

Other binoculars use what's called a porro prism. And what happens is that the light goes down through the eyepiece, gets reflected up to the other side, it gets reflected back down and in the process of going through that path, it inverts the image so that it appears right-side up. They're a little bulkier but actually these fit in the hand quite nicely and especially on modern designs like Antigua binocular. It's really compact and fits well so. The porro prism binoculars like this will tend to have a little higher light transmissibility and so at night they'll be brighter and they'll allow you to see dimmer objects than the roof prism style.

Quality of the Optics

One of the differentiating factors between binoculars that cost $100 and those that cost $300 or $500 or more is the quality of the optics. And the way that you notice this isn't so much how sharp the image is but it's really the efficiency of how much light passes through all of these lenses and prisms. So by coating the surfaces of the lenses and prisms with these really microscopic layers of chemicals or minerals, you end up with better light transmissibility. So for example on Antiqua binoculars they have a little bit of a green cast when you look at them. And what this does is cut down on the internal reflection on the lenses and makes them color corrected so that they focus perfectly for all frequencies of light. So one of the things that West Marine looks for our binoculars that are called fully multi-coated meaning that they have multiple layers on the glass surfaces in all of the lenses and prisms that are in the light path.

Adjustable Eye Cups

One feature that's common to almost all marine binoculars is adjustable eye cups. And they do this one of two different ways. Sometimes they sort of fold over the rubber portion folds down on itself, in other cases they spin up and spin down. This is kind of a nice feature and they have some intermediate locations. The reason they do this is because each binocular allows you to have your surface of your eye a certain distance away measured in millimeters from the eyepiece. And so if you have glasses on you turn these down and the glasses sort of move the binoculars away from your eyes but it still allows you to see the full field of vision. So this is called eye relief and modern binoculars will have a maximum eye relief of about 25 millimeters. Meaning that the eyepieces can be as much as an inch away from you the surface of your eye and still see the full vision. Another feature you might consider is that marine binoculars frequently have a built in bearing compass on them. And the way this works is that when you look through the left-hand eyepiece in this case. You'll actually see a compass bearing that's sort of floating at the top or the bottom of the image. That allows you to use this just like you would a hand bearing compass that you'd either hold at arm's length or what a little hockey puck compasses. And you can usually take a bearing down to about a 1 degree accuracy.

Stabilized Binoculars + Night Vision

There are two other products that fall into this general topic of marine optics. As we mentioned earlier one of them is the stabilized binocular. Although there are a couple of other brands as well. And these allow you to have higher magnification, because they have internal gyroscopes that somehow make the image look steady. So this might be a very very good companion to a normal set of seven by fifty binoculars.

Night-Vision Scope

The other item is to consider a night-vision scope. This is one this by floor this is a first mate. And what this does is actually not look at visible light it looks at infrared light. And by looking at the difference in temperature that different that objects put off. It allows you to see in total darkness, without any source of light, not even starlight, not anything ,it allows you to see for example people in the water if you've lost somebody overboard, it allows you to see bridges that would otherwise be invisible, even dead heads in the water will have a slightly different temperature and you can see them through it. So it's not actually light amplification, it's infrared radiation amplification and it works great. These don't provide a lot of magnification, that's not really the point, they allow you to see in the dark.

So I hope this how-to-by marine optics video has been helpful. you know most of us will end up with something that looks like possibly this, this is the Antigua, 7 by 50 binocular waterproof internal compass, really really compact, great set of binoculars, for under $300. Another choice in that same area our Tahiti binoculars - same general idea, high quality compass, waterproof, center focus, an extremely good set of binoculars, top rated by practical sailors several years ago. If you find that you don't need the compass consider one without a compass and you'll be saving 40 or 50 dollars and most of these models come in a compass or non compass model. And finally if you need something that's smaller for sports or just for general recreational use, consider one of the roof prism binoculars with a little higher magnification,n smaller lenses, more compact, very very handy and these obviously fit in the glove box of a car, fit in a small backpack they go anywhere with.