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Link to MyBoatsGear binocular section. GMDSS Global Maritime Distress & Safety System. Published by Adlard Coles Nautical.  Equipped
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Choosing Boating & Marine Binoculars
One of the items we always look at for boating activities are Marine Binoculars. 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.
Article quick guide
First thing to consider when looking at Marine Binoculars, is what are we 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 are marine binoculars 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.
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?
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 expresses the amount of the horizon you see through the binoculars. Say you are looking at a point on the horizon 1000 yards away these Specifications tell you that the image you are looking at covers a width of 390ft. Too small a field of vision and you will have a hard time finding what you are looking for.
This short video demonstrates field of view for binoculars
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.
Here is a chart of how binoculars and the numbers work together in various applications courtesy of just-binoculars. COM
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.
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.
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 7x50 WP marine binocular with compass and rangefinder
This feature-packed marine binocular includes a compass, reticle, rangefinder and individual focus. Celestron 7x50 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
Binocular Showcase from West Marine
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.
What about size and weight. Do you want a pair that can fit in a pocket then the Roof Prism is more likely to work.
Marine binoculars with 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.
Are they Waterproof, do they have Flotation straps, which are very handy if they are dropped overboard.
There are 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.
if you see the term Exit Pupil, Luminosity Factor, De-Alignment, Dioptric Correction, Oculars, Eye Relief, Resolving Power, Interior Focusing and many other descriptions and wondered what they mean this is the place to find the answer. Binoculars Etc
Sources of marine binocular reviews
Epinions Binocular 7 X 50 reviews
Motor Boat review of 7 x 50 Boat Binoculars with Compass
Practical Sailor: Binoculars over $300
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Another type of marine binoculars are image stabilized binoculars Image stabilized binoculars newsletter Maybe you are like me and have a hard time reading an image through regular binoculars. Even using 7 X 50 marine binoculars I have always had a hard time seeing the image clearly, unless they were a very expensive pair with great optics and coatings.
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Nikon 
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.