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Choosing High Powered binoculars

One of the most frustrating problems with Fujinon 25x150MThigh-powered binoculars is the prohibitive costs which are the result of achieving good optical quality. To the general user it will be difficult to justify paying such high prices, especially when so many products (computers, electronics etc) are readily available today cheaper than ever before.

Monk Optics who have been Optical Specialists for over 20 years have always specialised in observation binoculars, but we have never compromised on optical performance for the sake of low prices. Consequently our sales have always been limited in volume due to the very high manufacturing costs required to produce such instruments. It has not been unreasonable to expect to pay many thousands of pounds for a high-quality, high-powered binocular.
Until now....

Binocular or Telescope?

It may be argued then that a telescope would be a natural compromise over binoculars, especially as you would expect to pay far less for such an instrument. Unfortunately most telescopes available today are too high-powered, giving poor light transmission, an extremely narrow field of view, poor resolution and are very tiring to use. These factors make objects difficult to resolve and therefore hard to find. Eventually fatigue will set in and the user will become more and more dissatisfied and frustrated with the telescope which will in time result in the instrument being used rarely or not at all.

For The Technically Minded

Research has shown that when it comes to viewing distant objects, two eyes are definitely better than one. Our powers of resolution and ability to detect faint objects are dramatically improved by using both eyes. In addition, colour and contrast perception are enhanced. In fact, many observers can enjoy up to a 40% increase in contrast of hazy objects merely by using both eyes.

How can this improvement be explained? The retina, consisting of rods and cones, converts the image into electrical pulses. The brain interprets the pulses and produces the image we see. With the brain relying on only one set of pulses inconsistencies in the signals will interfere with the final image seen. With two sets of signals to interpret, the brain is able to reduce interference (known as noise) by averaging the pair of electrical messages.

Eyepiece design; 45º angled or straight?

/Bj-100iBObservation binoculars come with either straight or angled eyepieces. The benefit of the angled design, usually 45º, is the ease of use and comfort of viewing. The angled eyepiece model is much more user-friendly, allowing more flexibility for people of different heights to use the binoculars without the need to continually adjust the tripod. It is also of benefit when the binocular is trained on the night sky. The straight eyepiece design model will require more adjustment of the tripod for each user and to a much greater height, possibly making the binoculars less stable.

Size of Objectives

The size of the objective lens is the most determining factor of the overall physical size and weight of the binocular. This is of greatest importance when considering the use and positioning of the binocular. An observation binocular with a 60mm objective lens will still be fairly portable whilst an observation binocular with a 100mm objective lens is far more suited for static use. The heavier the binocular the sturdier the tripod must be to support it, enabling the user to have a good vibration/shake free image.


The magnification of the binocular determines how many times closer an object appears than when viewed with the normal eye. However, the greater the magnification the more limited the field of view and the darker the image will be. This will make it harder to locate an object and place more strain on the eyes.Fujinon 15x80MT A lower magnification will give a wider field of view and the image will be brighter, making it easier to find an object and the viewing more comfortable and relaxing on the eyes. A magnification of 25x with a 100mm objective lens has been considered one of the best all-round high-powered observation binoculars for practicality and performance for over 50 years.

Light Transmission

The size of the objective lens and the power of magnification are the two major factors that determine the light transmission of the binocular. For example, 100mm (the diameter of the objective lens) divided by 25 (the power of magnification) gives us a figure of 4, which is the diameter (mm) of the exit pupil and indicates the amount of light reaching the eye. In general the larger the exit pupil diameter the brighter the binocular will appear and the better the resolution will be, enhancing colour and contrast perception, especially in low light conditions. However, as the human eye pupil dilates on average from 2.5mm to 7mm depending on light conditions it follows that an exit pupil above 7 is not beneficial as the human eye cannot accommodate it.

It is worth mentioning here that as we age our eye pupil does not dilate so much, so a large exit pupil of 7mm is not so important for a 50 year old person compared with a 19 year old. So a 4mm exit pupil on a 25x100 observation binocular will be more than satisfactory for most users in most conditions, whereas a 40x100 will only give 2.5mm exit pupil, drastically reducing the amount of light reaching the eye.

Light Conditions

Whilst the size of the objective lens and the power of magnification are major factors in determining the light transmission of a binocular, the surrounding light conditions are also very relevant. If the binoculars are to be used in poor light then a lower magnification would be advisable to maximise the amount of light transferred. In good light conditions a higher magnification can be afforded, remembering though that the higher the magnification the smaller the field of view will be, resulting in objects being harder to locate.

Quality and Cost

The phrase "the more you pay the better you get" is true to a certain extent when buying observation binoculars. It applies largely to two areas: the construction and the optical quality. The construction must be sufficiently sturdy to ensure that prisms are not easily knocked out of collimation (i.e. both halves of the binocular are looking in precisely the same direction) and to ensure that seals against moisture are maintained. The tripod chosen must also be of a very sturdy construction to support the binoculars safely and provide a vibration free image.

The lens and prism quality together with the type of coatings applied to them will determine the optical performance of the binoculars. To obtain aberration free images both the objective and the eyepiece lenses have to be of multi-element construction. However at each face of every element light is scattered by unwanted reflection and to reduce this each face must receive an anti-reflection coating. The quality and complexity of this coating determines the brightness and contrast of the viewed image. A high quality observation binocular will combine careful lens design, precise optical coatings and exacting collimation to make the viewing as comfortable as possible with minimum eye strain.

Monk Optics have selected a range of three different brands of observation binoculars: Fujinon, Miyauchi and Monk. We believe that each of these will fulfil the need of most users of high-powered binoculars. Whether it is for performance, price or physical size.

The Fujinon Range

The Fujinon range is the most expensive and includes one of the largest objective lens binoculars available today (150mm). These binoculars with their tripod are huge and are chosen by the more specialist user for astronomy and commercial use or by the very enthusiastic observer.

The Miyauchi Range

The Miyauchi range is much more user friendly, due to their compact size and versatility. They are perfect for tripod mounted, long range terrestrial use, as well as starting binocular astronomy.

The Leviathan Range

.This is an exclusive range of Chinese observation binoculars of exceptional optical quality. These come complete with tripod and case at much lower prices than ever before and yet contain some of the best quality optics we have ever seen in observation binoculars at any price for over 20 years.

Realistically if binoculars of this quality were produced in the West or Japan, one would expect to pay at least two to three times the price.

Magnification; 25x or 40x?

The 25x magnification will give high resolution and high light transmission in all conditions, ensuring good detailed clarity for long distance viewing. With the wide angle and good depth of field spotting objects is quick and easy. In good light conditions the high power 40x magnification will give nearly double the magnification, but with a much narrower field of view.


Pedestal Mounted with Coin Operated Option

This observation binocular with coin-operated option comes complete with its own pedestal and base, designed for fixed position use, whether indoor or out. This makes them ideal for any situation where heavy traffic use, good security, safety and ease of use are important factors, such as hotels, cruise ships, observation towers and marinas.

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