Lets take a look at the basic information any captain will require before purchasing a pair of Boating Binoculars.
New models are always being introduced by manufacturers such as Steiner, Nikon, Navy One, Bushnell, Tasco and dozens of others...
Binoculars in general are designed for many uses, in marine applications our focus will be on the best features to select for navigation. Binoculars on small vessels primary task is to help us as navigators to see objects such as navigation markers and buoys, sandbars and rocks, other approaching vessels and landmarks.
Many optical dealers and other stores specializing or including binoculars in their inventory specialize in binoculars used for many tasks such as birding, hunting and astronomy. These types of binoculars are too powerful for the marine environment.
Marine binoculars are usually designed to take into account the fact that small boats are not stable. When you are tossing about at sea or even tipping a bit on a lake, a high powered set of binoculars (over 10x) intended for astronomy or birding would be overkill and trying to focus on any object with these types of binoculars would be nearly impossible.
7 x 50 is the Standard power of marine binoculars. The number 7 indicated the magnification - 7 times what the human eye can see. The number 50 is the diameter of the objective lens (the larger lenses at the opposite end to the eyepiece) measured in millimeters. This determines how much light it can gather for effective viewing. The larger the lens (higher number) allows a greater amount of light to pass through giving a brighter image. Larger objective lenses will give you the greater amounts of light but result in heavier and larger Binoculars.
These standard specifications are generally accepted as the best combination for small boat binoculars. Large vessels sometimes use 10x power binoculars to see at greater distances but for our purposes 7 x 50 is the best choice.
How do Binoculars Work?
Binoculars work like two telescopes mounted side by side. At the front of each telescope is an objective or a field lens. This gathers light from the object you are looking at. The larger the field lens, the more light gathering capability the binoculars will have. This is important for night navigation. Be sure to select binoculars which work well at night because that is when you will appreciate them the most.
After the light passes through the objective lens it light travels down the tube, and through a lens in the eyepieces, magnifying the image even further. If the binoculars are of a high quality there may be more lenses within the tube called elements. These additional lenses will work to your advantage in refining the image and gathering the most light possible. More elements equals better binoculars at a higher cost to you...Weigh your options but binoculars are not generally something you want to be too frugal about when considering a purchase.
Binoculars are built around a frame that houses the two telescopes and are generally hinged to allow for adjustment for each person.
Some binoculars are permafocus and never need adjustment. While others have a focusing wheel in the center to allow for manual focusing and a greater degree of fine tuning for sharper images. These are the types of binoculars most boaters are more accustomed to using.
The best binoculars have separate focusing capability for each eyepiece (known as Diopter Control) which allows for fine tuning the focus for each eye. When you have the diopters adjusted for your eyes no further focus adjustment is required. This is the best type of binoculars for use by serious captains. Let the crew use a set of center focus binoculars and you keep your diopters set for your eyes for when you need them the most.
Zoom?
Some captains choose zoom binoculars as the primary set for their vessel. This type can be adjusted to give you varying ranges of magnification. For example, a binocular that is listed as 7-21x40mm means the zoom portion is capable of viewing at 7x power minimum and can be adjusted up to 21x power and the 40mm would be the objective lens size. Remember that magnifications over 10x - 12 x are very difficult to hand-hold. In which case, a sturdy tripod is highly recommended.
Zoom binoculars are better left in the hunting camp or bird watching bag. Whenever a fine piece of optics is designed to do all things for all situations, compromises are always made. In general, zoom binoculars are more cheaply made, have a higher chance of becoming fogged up in bad weather and are more of a marketing gimmick than a useful tool on a boat.
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 multiple lenses.
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.
Porro prisms Binoculars are distinguishable by the narrower eye piece than the objective lens. The resulting jog in the light path being deflected through 180 degrees twice by the two prisms in the housing.
Roof prisms are indicated by the two straight tubes making them more compact and easier to hold. The Porro prism rendered better contrast and was still favored by purists for a long time after the advent of the roof prism but new technology of roof prisms has improved greatly, which makes newer models a better value.
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.
Points to consider when buying Binoculars
Fit; Try them on and make sue they fit your grip and fit your face comfortably. Try them out in daylight and at night if relevant.
Coatings, if you look at the water surface, you will notice the glare of the sun shining on it. Lens coatings remove glare and allow more light to enter the optics. The more coatings a pair of Binoculars have the more expensive they are. Cheaper Binoculars do not have the coatings as better models and this can account for the wild variation in prices.
Focusing; which type of focusing is best for you? Center Focus with a wheel. The center wheel focuses at the same time for your eye, or can 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 choice is more likely to work.
Do you need a compass? Binoculars are more expensive with a bearing compass but there are benefits such as easy position fixes. Try compass position relative to your grip.
Are they waterproof, do they have Flotation straps, which are very handy if they are dropped overboard?
Price & Summary
Price is not the over-riding factor when choosing good binoculars. While you do not need to buy the most expensive brands you should purchase binoculars based upon the necessity they represent. When you are navigating your vessel, at night, with the lives of your family and / or guests at stake, do you really want to place your trust and make split second decisions based upon information you gain via cheap optics? Comfort, light transfer, clear optics and reliability are the primary factors you should use to judge your binocular buying decisions, not name brand, fancy features like zoom capabilities, compasses or internal lighting.
Choose the most reliable, brightest and best protected binoculars you can find. You will not be disappointed.
By: Scott Pooler
Portions of this article Sourced: http://EzineArticles.com/?expert=Mike_Hobson
