Frequently Asked Questions

The first number on a binocular indicates the power or magnification. An 8×40 indicates a magnification of 8x, so whatever you are looking at appears to be 8x closer or bigger. One of the biggest mistakes in choosing a binocular is to select too much magnification. Although a bigger magnification makes the scene appear much closer, there are disadvantages. Bigger magnifications are harder to hold, so the image is shaky, and larger magnifications produce much narrower field of view, so although you see things closer, you see less of it making it harder to view.

Higher magnification uses more light, so a highly magnified image will not be so bright, on balance, it’s important to select a magnification which is right for the job.

The OCULAR means eyepiece ( nearest the eye ) so the diameter of the ocular is just the actual diameter of the glass on the eyepiece lens. Larger diameter eyepieces ( like those on the Visionary HD ) improve quality of viewing, but many users get this confused with the diameter of the exit pupil.

The diameter of the exit pupil is the bright circle in the middle of the eyepiece. This is related to the magnification and size of the objective, and is roughly the objective diameter divided by magnification, so a 7×50 produces an exit pupil of (50/7) = 7mm and a 20×50 is (50/20) = 2.5mm. A bigger exit pupil makes the binocular brighter in low light conditions.

The human eye pupil opens up in low light and closes down in bright light, so, on a bright day it doesn’t matter if the exit pupil of the binocular is small, because the eye pupil is small. A 20×50 etc, will work perfectly well on a bright day. In low light, where the eye pupil opens up, binoculars with larger exit pupils perform better. However…. the maximum pupil diameter of the eye is about 7mm, so there’s no point in having a binocular with an exit pupil bigger than 7mm, because the eye can’t use it.

With this in mind, the optimum binocular for low light is a 7×50 or 8×56 or 9×63 or 10×70 etc.. There is another small but … as we get older the ability of our eye pupil to open reduces and some users may not see a significant difference in low light performance between an 8×40 or 10×50 ( exit pupil 5mm ) and 7×50 or 8×56 ( exit pupil 7mm ).

Most binoculars indicate an angle of view, either shown in degrees, or expressed as a number like 100m at 1000m. A wider angle means you see more of the scene you are looking at. Usually wider angles are found on lower magnification binoculars, an 8x should have a field of view between 6 to 8 degrees, but a 12x is likely to be only 4-5 degrees.

Tricky question that one because astronomy and birdwatching are totally different.The brief answer is yes a spotting scope with a large front lens can be used for both but I’ve given some more detailed thoughts below. I’d suggest minimum of 80mm objective, so from our range of spotting scopes the following models would be OK,

Visionary V80  ( 20-60×80 ) Visionary 80ED ( 20-60×80 ) Illusion i100 ( 25-75×100 ) Olivon T80 ( 20-60×80 ) 
Olivon T90  ( 23-68×90 ) Olivon T80ED ( 20-60×80 ) Olivon T90ED  ( 23-68×90 )

Now  the more complete answer :

Telescopes primarily designed for astronomy ( astroscopes ) tend be differently designed to those for normal terrestrial spotting ( birdwatching etc ) For astronomy it’s important to have really good light gathering and quite high magnifications can be needed to see detail in distant objects. It’s not so important on an astroscope to have close focusing, and usually astroscopes produce upside down images. ( when looking at things in the sky it doesn’t matter which is up and down ) Also the  tripods on astronomical telescopes are often of “equatorial” design, this means that they don’t have the usual ( side to side / up and down )head movement, instead the head tracks in an arc to allow for the movement of the earth. This type of tripod mount is great for astronomy but quite awkward for birdwatching. A normal tripod for birdwatching would be a bit slower to use for astronomy.

Other considerations are that good astronomical telescopes can be quite expensive, you really need something with an 6 inch ( 150mm ) objective lens or mirror ( some astroscopes use mirrors instead of lenses ) to get any decent light gathering, better still 8 inch or 10 inch, and a good solid tripod. Also atroscopes tend not to be water resistant ( you’d never use an astroscope in the rain because there would be nothing to see )

Now, having said all this, for basic astronomy ( looking at the moon, planets, odd comet etc etc ) you can get away with a smaller scope. There are quite a lot of astroscopes on the market with smaller lenses or mirrors, 76mm and 114mm are quite popular and not expensive and these will be OK.  But even so, these will probably have equatorial mount tripods and give an upside-down image so they are not so good for birdwatching.

A normal spotting scope ( like the Visionary V-series, Olivons or Illusion i-series ) produce clear, bright and normal upright images, are well colour balanced for nature viewing, they have more rugged body designs and waterproof. They attach to normal tripods allowing quick easy finding of subjects.  …. and, most importantly, a spotting scope with a good sized front objective will be at least as bright as it’s equivalent sized astroscope, and most of them have zoom eyepieces which get up to the same sort of magnification that you could achieve with an astroscope. In fact sometimes spotting scopes can be brighter because the mirror designs of many astroscopes don’t use the full size of the mirror to gather light
Because of this, for basic astronomy, a spotting scope of 80mm or above will work very well indeed.

Yes some of our models work in very low light, but don’t confuse night vision scopes with low light binoculars. A night vision scope is designed to work with little or no light and provide an image, These are black and white ( or more usually green ), low magnification and cannot be used in daylight A low light working binocular will work during normal daylight as well as in low light levels, and with more realistic magnifications, however lowest light level is moonlight or equivalent.

Yes, we can supply models suitable for schools and college use.
We do not supply directly to consumers, so, unless you are making a very large purchase it will be cheaper and faster to buy through one of our wholesalers or specialist dealers. Contact us and we will suggest a supplier or click here for our product specialists


Weatherproof and water resistant are really the same thing.

A waterproof binocular is designed to withstand submerging in water, whereas a water resistant/weatherproof will stand rain, but not depth of water under pressure.  All Optical Hardware/Visionary/illusion models conform to these definitions – if we say waterproof, it can be submerged, if we say weatherproof, it can held in the rain, but not submerged. Unfortunately, there is no industry standard on this definition, some manufacturers and brands use the word waterproof to mean that it will withstand rain, by our standards this is only water resistant.

By waterproof we mean it can be submerged in water, but this doesn’t mean it can stay underwater for a long period, water pressure will eventually force water into a waterproof binocular. The better the binocular is constructed, the longer and/or deeper the binocular can be held underwater. binoculars built to military specifications can usually withstand a depth of about a meter for up to fifteen minutes ( enough to allow wading through deep water with a binocular in a waist bag ).

A basic waterproof, would only stand a few cm of water for a minute or so ( enough to rescue it if dropped in a shallow stream ) Most waterproof binoculars are also “nitrogen filled” This means that there is a dry gas inside which prevents the binocular misting on the inside in low temperatures and damp conditions. Eventually however, the seals will deteriorate and the gas will leak out, so a nitrogen filled binocular will not remain filled and the instrument not fully waterproof. They can be recharged, but this is often costly and for lower price binoculars it probably isn’t worthwhile, and the binocular will still work perfectly well under normal conditions.

It’s worth bearing in mind that there is no industry standard on this definition, some others say their binoculars are waterproof but by our standards this is only water resistant. 

Also please bear in mind, it is not possible to nitrogen fill or waterproof the eyepiece section on telescopes with interchangeable (removable) eyepieces.

Coatings are applied to lens and other component to increase light transmission. All instruments supplied by us have some coated lenses however more expensive models have more or better coatings.
FC ( Fully coated ) means all elements have some coating applied.

MC ( multi-coated ) means some of the elements have multiple layers of coating to achieve better results.

FMC ( fully multi-coated ) means that all the elements have multi coating.

Phase coating is a process applied to the prisms in more expensive DCF designs.

It’s not surprising the user had problems with this, the requirement is very difficult to achieve. I’ll try to answer the question fully by sharing the issues you need to overcome and giving some indication of how you might do this.
The answer also applies to any very long distance viewing.

First, magnification. To view something 35,000ft away requires quite high magnification. 100x would make it effectively appear 350ft away, You’d probably be OK seeing the detail of an aircraft at around effectively 1000ft-1500ft so you could get away with magnification of 25-35X but this is still quite powerful and there is a problem, with high magnification, three things happen.

1. High magnifications effectively restrict brightness, so the image will not be so clear
2. High magnifications are difficult to hold still
3. High magnifications give a narrower field of view.

When viewing a distant moving object you need a wide field or you will not be able to find the thing you want to view, and if the magnification is high the instability of the image will be such that you are unable to see the detail.

Brightness As the magnification increases the brightness of the image decreases. Brighter images give better viewing clarity especially in lower light. If you are viewing an aircraft, unless the sun is in the right position, the side you are viewing could be in shadow. You can get more brightness by having a bigger objective lens. So, for example, a 20×60 will be better in this situation than a 20×50, but bigger lenses mean a bigger binocular or telescope which is harder to hold still and you are back to the problem of viewing a stable image.

Air Clarity 35,000ft is quite a long distance. The air is usually not totally clear and viewing clarity is reduced by mist, dirt and haze. There is nothing you can do about this no matter what optic you choose.

Keeping it still Most users can comfortably hand hold up to 12x magnification. With practice it ispossible to hold up to about 20x. Above this you really need a support – a tripod,monopod or handgrip.

Binocular or Telescope ? Binoculars can give a better, brighter, image because they are using both eyes, but are bigger and heavier than their equivalent size and magnification in a telescope. A telescope will give you more magnification and a bigger objective lens size in a practical sized instrument.

Taking all of the above into account I would suggest that there is little point in buying a very expensive instrument because, no matter how good the optics, you’ll not get the full performance through 35,000ft of unclear atmosphere.

If you want to hand hold, I would suggest a 20x binocular, though this might not quite give you enough magnification. The Visionary Classic 20×60 is fairly inexpensive, the Visionary HD 20×80 has bigger lenses and so gathers more light, quite a lot of aircraft spotters use the HD 20×80 model. Both would require practice to hold still

If you are prepared to use a support then a telescope would possibly be better. Select a telescope with an in-line eyepiece ( not 45 degree ) Up to about 60mm can be hand held at modest magnifications, and all will accept a handgrip. The Olivon handgrip is a good choice.

At modest cost the Visionary V60ST gives 15x to 45x variable magnification with a 60mm objective lens. We also have the Visionary AIRMAN-60 which gives 20x to 60x magnification, really good optics and this was introduced with aircraft spotters in mind, though it’s a bit more expensive.

If you are prepared to use a tripod then you could go for a larger telescope such as a Visionary 70ST or 80ST. Select a very solid tripod with a very smooth flowing head, for example Olivon 159 with perhaps a 14 or 16 head would be OK

No, absolutely not.  Magnification is a complicated subject and we cover much more detail in our technical sections but to summarise : The maximum magnification of a telescope is governed by a number of factors including the size of the objective lens or mirror, eyepiece used, quality of optics and observing conditions but for technical reasons this hits an upper limit. Even with the best of the best this is about 600x which is not sufficient to see such small detail on the moon.