Binoculars
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Marine
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A GUIDE TO CHOOSING BINOCULARS FOR MARINE USE

What size do I need and what do the numbers mean?
Monk Nautilus 7 x 50It might appear to the layman that choosing binoculars for marine use is totally confusing and mind boggling with all the different considerations of magnification, size, light factors, waterproofing, anti-reflective lens coatings, angle of view, rubber armouring, integral compass etc; but there are general rules of thumb, which can be followed to narrow down the selection very easily.

The first thing to remember is that the 7x (seven times) magnification is acknowledged to be the maximum strength that can be handled satisfactorily at sea, due to the motion of the boat. (The new FUJINON TECHNO-STABI - stabilised binocular is now available which Fujinon Tecno-Stab 14xallows a 14x magnification) Anyone who tells you that they can use a 10x 50 quite comfortably on their boat must be either totally becalmed or chugging down the canal.

So, accepting that 7x is the most appropriate magnification (this is the first number that will appear on the binocular) we must then decide what size objective lens we require. This is the wide lens at the far end of the binocular, from which the light is transmitted. For marine use this will usually be 50mm in diameter. Hence we get the size 7x50 and this is the most universally accepted size of binocular for marine use. This combination of magnification and lens size provides a steady image plus the maximum diameter of transmitted light that the human eye can accept.

It is possible to reduce the size of the objective lens in order to make the binocular physically smaller and lighter e.g. 7x42, 7x35, and 7x26 Even the smallest of these will provide a very acceptable image, provided you are sailing in fine daylight conditions but in poor light or twilight it will become more difficult to distinguish objects and colours. (The lightweight MONK EXPLORER 7x26 for example make an ideal second pair of binoculars that can be worn around the neck or carried in the pocket for use on land or at sea.).

So now we have narrowed down the main choice of binoculars to 7x50. Most 7x50 binoculars have a field of view of approximately 7° (seven degrees). This indicates the width of the vision you will see from side to side of your image, this angle is quite acceptable for marine use.

Waterproof or non- waterproof and how much should I pay?
Monk Nautilus 7 x 50 CompassThe next point to consider is whether or not you want a waterproof binocular. If it is going to be totally waterproof (which should be nitrogen filled) then the cost will usually be over £100. It must be emphasised here that just because a binocular has a rubber covering it does not necessarily mean that they are waterproof. The rubber covering itself only helps to protect against accidental knocks and provides a firmer non-slip grip if the hands are wet. The waterproofing is in the actual construction of the binocular. Usually if the binocular is fully waterproof it will be printed on the binocular or it will say nitrogen filled.

You may feel that non-waterproof binoculars will be sufficient for your needs as you never expect to get them wet with rain or sea-spray, but we would emphasise here that because of the environment in which the binoculars are being used, moisture will gradually get into any binocular which is not completely sealed. Eventually mildew will form on the lenses and prisms and the performance of your binoculars will slowly deteriorate becoming less bright and less clear. A quick check on your binoculars is to look through the wrong end of the glasses holding them about 12" away from the eyes. If they are not crystal clear inside the performance will be impaired to some degree.


.Centre focus, fixed focus or individual focus?
Most waterproof binoculars have an individual-eye focussing system. This is not as awkward as it may first seem. Because we are using a
7x50, the binocular will have a very good depth of field i.e. everything from about 20 metres to infinity will be in focus provided the eyepieces are both set on the –1 (minus one) diopter marks. This setting will be correct for all normal sighted uses. This feature can prove extremely useful since all crewmembers will be able to look through the binoculars without having to make any adjustments and it can be particularly advantageous if you are in a hurry or sailing in adverse conditions. It would be reasonable to expect individual eye focus and fixed focus binocular to give a longer service, greater reliability, better waterproofing due to less moving parts

7x50's are an ideal size for focus free binoculars due to their excellent depth of field, making focus unnecessary for the majority of users. Only spectacle wearers who take off their glasses may have problems with this type of binocular, in which case it would be recommended to keep spectacles on.

Non-waterproof binoculars usually have a central focus wheel with a separate right eye adjustment to correct for uneven eyesight. This type of binocular can either be rubber covered or leatherette type finish.



Spectacle wearers
Most binoculars today are fitted with soft rubber eyecups.Fujinon 7x50 FMTR-SX These rubber eyecups should be folded down for using with spectacles in order to enjoy the same field of view as non-spectacle wearers - the FUJINON 7x50 FMTR-SX is probably one of the finest binoculars for spectacle wearers due to its very large ocular eyepiece and flat field. It will not be necessary to alter the focus setting described above but of course if the spectacles are taken off adjustments to the binocular focus will have to be made.

Quality
After deciding whether the you want waterproof or non-waterproof binoculars in either case you must now look for clarity, brightness and comfort of use. Generally speaking the more money you pay the better the lenses, prisms and body construction, but in any event if the binoculars pull or strain the eyes do not buy them. This usually means that the prisms have moved and need to be re set professionally. (See our repair department) Always be sure to check the actual binoculars you are buying. If you go to binocular specialists they will normally be able to determine immediately if the instrument is correctly aligned but an inexperienced salesman may not have the practised eye at determining whether a binocular is slightly out of collimation - double vision - and you may have difficulty getting your money back or the goods exchanged.

More recently binoculars are now becoming available from places like China where prices are incredibly low. As new technology keeps advancing and labour costs are kept low you may wonder what's the point of paying much higher prices for a similar product. Usually much better materials like all glass lenses not plastic will be used, and the binocular body will probably be made of aluminium or similar, instead of plastic. Consequently you should get a much better optical binocular in a well-protected housing that should give you many years good service.

Beware of long guarantees on low price binoculars, as it will be difficult for you to prove that you have not abused them. The most common fault on all binoculars will be the dislodging of the prisms - double vision or eyestrain - which can only happen when they have been knocked - it cannot happen on its own! So the cheaper the binocular the more likely it is to happen.

Lens coatings
In recent years the coatings on binoculars have improved to the point where 95% light transmission can be obtained over the visible spectrum (early binoculars only transmitted about 50% of the light received). This means that of the light striking the front (objective) lens 95% emerges from the back (ocular) lens to your eye. The benefit is outstanding vision in low light and at night – an especially important consideration in marine application. One of these binoculars is the FUJINON 7 X 50 FMTR-SX reputed to be the worlds brightest binocular. Generally speaking a light transmission of between 70%-80% will be achieved with most modern good quality binoculars.


Monk Argonaut BIFOne of the most popular 7x50 waterproof binoculars is the MONK ARGONAUT III. This model gives a good clear image, very good brightness is very robust and totally waterproof. At around £329 it represents excellent value for money – a good midpriced binocular. At the cheaper end of the market in the non waterproof range the VISTA focus free range at £59.95 are very good value for money and certainly out performs other binoculars in the same price category for clarity, brightness and robustness.

Compass Binoculars
There is no doubt that compass binoculars have become very popular for marine use. The early types were not always successful as some of the compasses were not very satisfactory but in the past few years there are been vast improvements in the compasses incorporated. The FUJINON PRO-45 and the MONK ARGONAUT III (see "YACHTING MONTHLY" magazine review) binoculars now use Silva's 45mmArgonaut II BIF compass, made in Scotland, renowned for their precision and reliability. They are extremely well damped and accurate to +/- 1°. Both binoculars use a beta light in the compass for night sailing, which guarantees no influence of magnetic parts near the compass. There is no doubt that when looking through binoculars for a buoy or marker being able to take a bearing at the same time makes practical sense. If a separate hand-bearing compass is used there will be times when you are unable to locate your object without the aid of binoculars. This is especially true in dull light condition when a good 7x50 will enable you to see more than the naked eye.

Some people may find that it takes a little while to get used to using compass binoculars. The compass scale will appear in the top or lower quarter of one of the lenses as you look through them and the trick is to practise looking straight ahead at your object through the binoculars and read the compass bearing at the same time, rather than looking down at the compass scale and up again at the object. Taking a mean average of the readings will produce a remarkable degree of accuracy at sea.

Fujinon 7x50 FMTR-SXIt is worth noting that compass binoculars available in the U.K. are usually suitable for use only in the Northern Hemisphere but here at MONK OPTICS we can supply compass binoculars for either hemisphere.

Why buy binoculars from Monk Optics?
Twenty years experience in the optical industry and our commitment to providing expertise knowledge and service has earned us the enviable reputation as one of the most respected and trusted binocular specialists in the country. Our commitment to improving and perfecting products has always been on our agenda. Both the Fujinon PRO-45 and the Monk Argonaut III for example have evolved through the continuous development, research and customer requirements for the near perfection obtainable in compass binoculars. Our continual improvement and growth has been achieved through our reputation, enthusiasm, word of mouth, with very little advertising being necessary. All products sold are selected for their optical quality, performance and reliability and where possible retaining value for money. Monk optics will only sell heavily advertised branded products if they are considered optically superior or outstanding value for money.

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