Binoculars for Boating

Binoculars for Boating are not everyday binoculars because we have special needs. Binoculars help us navigate, spot wind, fish, weather and just enjoy the scenery. There are always new models on the market, but the inherent binocular design is still the same.

Here we take a look at what you need to know when looking for Binoculars for your boat.

First thing to consider when looking at Marine Binoculars, is “what we are going to use them for”. We mostly use them for Navigating which means we need to be able to spot channel markers and objects in the water.

Most places specializing in Binoculars cover birding and hunting and astronomy which are too powerful for the marine environment. Boats are not stable and so anything with a power over 7 is going to have a blurred image due to hand shake or boat movement. Buy from a purveyor of marine & boating Binoculars and make sure you try them.

We look at how binoculars work, then we look at what all those numbers mean i.e. 7*50 what does that mean, and why marine binoculars are rated 7 * 50. Next we look at the prism types. For example what does Roof and Porro Prism mean. To help explain we have a Chart of binocular types for various uses and sports. Next we look at some quality Marine Binoculars.

Another important specification you will see for binoculars is field of view

When looking at Marine Binoculars here are some other Points to consider. To help we have a source of Binocular terminology. Interested in reviews here are Sources of Boat Binocular reviews from Motor Boat and Practical Sailor.

How Binoculars Work

Internal Diagram

This diagram is courtesy of Yesmag and shows how the objective lens and eyepiece lenses work together with the prisms without which the image would be upside down.

Binoculars are like two telescopes mounted side by side. So, how do telescopes work?

At the front of each telescope is a lens either an objective or a field lens. This gathers light from whatever it is you’re looking at. Let’s says you’re looking at a bird. The objective or field lens magnifies the image of the bird, but this image is upside-down. Not very useful at this point.

If you are using prism binoculars (and most likely you are as they are the most popular kind), a prism in each tube reverses and inverts the image of the bird. In field glasses, there is a second lens instead of a prism.

The light then travels down the tube, and through a lens in the eyepieces. The bird is magnified even further. Good binoculars will give you an accurate and detailed look at the bird.


What do the numbers mean

This description is brought to you from just-binoculars. COM

Binoculars are often specified by a set of numbers such as 7 X 35 or 8 X 40, the first number indicates the strength of magnification (how many times closer the subject is to you, 5 times closer, 7 times closer, 10 times closer) and the second number is the size of the objective lens measured in millimeters going across the lens. The size of the objective lens will determine how much light it can obtain for effective viewing. The higher the number, the larger the lens; in effect allowing more light to pass through thereby projecting a brighter image and viewing experience.

Zoom Binoculars work on the same principle as regular binoculars except that the power can be adjusted to give you varying ranges of magnification. For example, a binocular that is listed as 10-22x50mm means the zoom portion is capable of viewing at 10x power minimum and can be adjusted up to 22x power and the 50mm would be the objective lens size ( the larger lenses at the opposite end of the binocular ). When considering zoom binoculars remember that a larger objective lens would fair better giving you the greatest amount of light gathering, however they will be bigger and heaver also.

Binoculars are built around a frame that houses the two telescopes and is generally hinged to allow for adjustment for each individual viewer. Some binoculars are perma focus and never need adjustment, just pick up and use them. While others have a focusing wheel in the center to allow for manual focusing and a greater degree of fine tuning for sharper images. Some models also offer focusing systems on each eye piece and once adjusted they are set for that viewer. Separate focusing of each eyepiece ( known as Diopter Control ) is also available in some types of binoculars, which allows for additional precision.

You will find most Marine & Boating Binoculars are rated 7 x 50. This is because of the uneven surface the user is operating in. Bouncing around on a boat a magnification higher than 7 would result in a blurred image. The best marine binoculars are 7 * 50.


Field of View

Field of View is expressed in feet and is the amount of the horizon you are seeing through the image. Typically the field of view is expressed in feet at 1,000 yards. Field of View can also be angular, typically 5 to 11 degrees for Binoculars.

Popular Steiner Binocular Specifications    
7 x 50 Item no 395.
Weight: 39oz
Field of view: 390 feet @ 1000 yards
Eye relief: 22mm
Dimensions: (inches) 5.2L x 8.2W x 3.6H


Prism Types

Prisms are used to condense the viewed image for maximum magnification in a short space. Prisms recreate an image of the original that is much purer than any image you would get from mirrors or multiple lenses which could magnify the image in a shorter distance. The resulting distortion would render the image impractical.

There are two kinds of prisms used in binoculars: roof prisms and Porro prisms. You can tell which type of prism is used from the shape of the binoculars.

Just-Binoculars Prism diagram

Porro Prism Binoculars with Porro prisms have a jog in the light path that results in the eyepiece being much smaller than the barrel of the binoculars, as seen in this diagram:

Roof Prism

Roof prisms result in an exterior design of the binoculars that is more like two straight tubes. The roof prism design was perfected in the 1960s; binoculars with this design are compact and easier to hold. For a while after their introduction, roof prism binoculars required much greater optical precision, so they cost more to manufacture. The Porro prism rendered better contrast and was still favored by purists for a long time after the advent of the roof prism. The technology of roof prisms has improved greatly since their debut, which makes newer models a better value.

BAK-4 prism

The BAK-4 prism is made of a high quality glass and produces sharp images and good edge to edge sharpness. . Generally, higher quality binoculars will use BAK-4 prisms in the construction process. Phase coated prisms take it one step further, the coating process enhances the resolution and contrast of images coming through the binocular and are generally applied only on more expensive binoculars.


Binoculars application Chart

Here is a chart of how binoculars and the numbers work together in various applications courtesy of just-binoculars. COM




Binoculars Manufacturers

Steiner 7×50 Commander XP C Binoculars w/ Compass 395

Steiner marine binoculars were the first to bring a compass to the marine Boat Binocular. The XP optics Steiner claim, keep the images sharp even in poor light. The lenses are treated with a protective coating to resist scratching and repels water. Each pair has 3 eyecups so you can choose the right one for you. Waterproofing is to 10m and Steiner’s auto focus system are among the many features. Retail price for the XP $1,300 compared to Steiner Commander V’s $1,600

You could go with the Steiner Observer model which retails around $450 and is also very good and is reviewed in the Motor Boating review below.

One thing you will notice about Boating Binoculars is the large variation in prices for what looks like the same features. With Marine Binoculars the optics and coatings can add dramatically to the cost, but also add dramatically to the image especially in low light and reflection of the water. Using the Commander XP from Steiner, you will find the image is very clear and not blurred. So if price is not a concern this is a good marine binocular.

Cheaper Options from Steiner include the; Navigator model retail and Observer model


Nikon Sports 7*50 marine binoculars w compass

These nitrogen filled and O-ring sealed binoculars are 100% Waterproof & Fog proof. With the new UCC lens coating giving you 95% Light Transmission, BaK4 prisms and multicoated lenses, you can see what you need to see! The built-in compass is just another one of its fabulous qualities! $590 retail.


Fujinon Polaris FMTRC-SX 7*50 marine binoculars

The Fujinon “SX” series Boating marine binoculars, every lens and prism surface is coated with a special new EBC process. The result is an overall brightness factor of 95% across the full visible spectrum. The benefit is outstanding vision in low light and at night, an especially important consideration in marine applications. To improve water and fog resistance, the housing is dry nitrogen filled and sealed at the factory. With compass the list is $1,160


Celestron 7×50 WP marine binocular with compass and rangefinder

This feature-packed marine binocular includes a compass, reticle, rangefinder and individual focus. Celestron 7×50 WP-IF/RC is Waterproof & Fog proof Porro Prism Binocular (7.0-Degree Angle of View). The 7 x 50 boating binoculars include BAK-4 prisms and multi-coatings for sharp images. Oceana 7 x 50 IF/RC Reticle/Compass Binocular belongs to Oceana Series from Celestron that features waterproof models for marine use.

The rangefinder is a useful tool for boaters allowing you to figure our range and size. Most rangefinders require you to know the size of the object such as a lighthouse height.


Bushnell 7 x 50 marine binoculars

h2o® Marine Boating Binoculars

Bushnell marine 7 x 50 binoculars Features

  • BaK-4 prisms for bright, clear, crisp viewing
  • Multi-coated optics for superior light transmission
  • 100% waterproof: O-ring sealed and nitrogen purged for reliable, fog-free performance
  • Non-slip rubber armor absorbs shock while providing a firm grip
  • Fold-down or twist-up eyecups
  • Large center focus knob for easy, precise adjustments
  • Longer eye relief



Swarovski 7 x 50 boating binoculars

SLC 7*50 B Roof Prism Binoculars, no compass.

Women tend to find the roof prism easier to hold.

Handy, ergonomic and exceptionally versatile – the SLC binoculars by Swarovski Optik are among the most-used binoculars ever. But the SLC series can now offer a multitude of tangible benefits. SLC new – this means an innovative design with improved ergonomics – for greater versatility and functionality

The focusing is via a center wheel. There is another knob to provide dioptric correction between eyes. The process of correcting for your eyes is to look through the binoculars and close the right eye and set the focus for the left eye with the center focus wheel. Switch eyes and correct for the right eye with the dioptric knob. Expensive at $1,450 retail


Points to consider when buying Boating & Marine Binoculars

  • Try them on and make sue they fit your face comfortably the grip also. Try them out in daylight and at night if relevant.
  • Coatings, If you look at water with the sun shining on it, you will notice the glare. Lens coatings remove glare and allow more light to enter the optics. The more coating the more expensive the Binoculars. Cheaper Binoculars do not have the coatings as better models ands this accounts for the wild variation in prices.
  • Focusing. Center Focus with a wheel, The center wheel focuses at the same time for your eye. Or do they compensate for unequal vision. This is by means of a dioptric correction through the adjustment of one eyepiece, usually the right-hand eyepiece.
  • Size and weight. Do you want a pair that can fit in a pocket then the Roof Prism is more likely to work.
  • Do you need a compass. Binoculars are more expensive with a compass but there are benefits. Marine binoculars with illuminated compass, help in navigation. Compasses can be found with a bezel style or digital.
  • Rangefinders are also useful. To use a range finder, you divide the height of an object that you know by the points read on the reticle scale when you look through the binocular. Example: A lighthouse is known to be 150 feet high, and appears to be 15 points on the vertical scale of the reticle. 150/15 = 10, so the distance from your point to the lighthouse is 10,000 feet.
  • Waterproof and Floatation; do they have Flotation straps, which are very handy if they are dropped overboard.

There are so many places to look online for binoculars its confusing. However its also a great source of information. The downside is you cannot try them on unless you already have tried them.