Optical Hardware | FAQ's - Freqently asked questions

The page below gives answers to the common questions we are asked and we are adding to it all the time.  We get some many questions about digiscoping, we have created a special digiscoping FAQ page so if your question is about DIGISCOPING please click here.
All other questions are covered below.


1/ How important is magnification ?


The first number on a binocular indicates the power or magnification. An 8x40 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, itís important to select a magnification which is right for the job.


For more detailed information check out our technical guide, or our more detailed technical guide


2/ What does Ocular diameter mean ?

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 7x50 produces an exit pupil of (50/7) = 7mm and a 20x50 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 20x50 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.

BUT, 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 7x50 or 8x56 or 9x63 or 10x70 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 8x40 or 10x50 ( exit pupil 5mm ) and 7x50 or 8x56 ( exit pupil 7mm )

For more detailed information check out our technical guide, or our more detailed technical guide


3/ What does field of view mean ?


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.


For more detailed information check out our technical guide, or our more detailed technical guide

4/ Are there any telescopes which are equally good for astronomy and bird watching

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  ( 20-60x80 ) Visionary 80ED ( 20-60x80 ) Illusion i100 ( 25-75x100 ) Olivon T80 ( 20-60x80 )
Olivon T90  ( 23-68x90 )
Olivon T80ED ( 20-60x80 ) Olivon T90ED  ( 23-68x90 )

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.

For more detailed information check out our technical guide, or our more detailed technical guide
and for more information about the differece between astronomical telescopes and spotting scopes, please
click here

5/ Does "waterproof and nitrogen filled" mean that a binocular or scope is FOGPROOF and is waterproofing covered under guarantee

The expression 'fogproof' is often misused these days so we don't use it quite so much in our publicity material, but basically any fully waterproof and nitrogen ( or equivalent ) filled instrument should dramatically reduce condensation on the internal optical elements.  

It isn't possible to seal instruments forever, there will always be some leakage of the dry gas so it is necessary to recharge this if you wish to keep the instrument waterproof. This isn't covered under guarantee as it's normal usage.  Also, please note that with any instrument with interchangeable lenses ( which includes  most scopes) you can' fully seal the section around the eyepiece so there may be some fogging here which should clear quickly.

6/ Do any Optical hardware models Ďsee in the darkí


Yes some of our models work in very low light, but donít 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.


7/ Does Optical Hardware supply directly to the public ?


No, but we will always help you find a dealer. Click here for our stockists 
For a more detailed discussion about why do not supply directly, please click here


8/ Iím a teacher and want to buy a large number of binoculars for class use


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 willbe 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

who can advise best models to suit your needs and budget, and orders can be placed on a school or local authority purchase order, or by cheque or credit card if you prefer.


9/ What's the difference between waterproof and  water resistant and weatherproof?


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 iit will withstand rain, by our standards this is only water resistant.


10/ How waterproof is "waterproof"


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.  See question 5 above. It's worth bearing in mind that there is no industry standard on this definition, some other  use the say their binoculars are waterproof but by our standards this is only water resistant.
Also please bear in mind on telescopes with interchangeable (removeable) eyepices, it is not possible to nitrogen fill or waterproof the eyepiece section


11/ I want an Olivon hide-clamp but I'm confused a, you list a "clamp" but this seams only to be G-cramp, not a full useable tool for my telescope, other manufacturers sell the complete unit. Can you advise ?


The Olivon can be bought as a complete unit ready to use, or you can buy parts and sections to tailor the unit to your exact needs.


You require : clamp +  column + head.


The clamp is the basic part wihich fixes to the table. The column fits into the clamp and slides up and down to the selected height. The head fits on top of the column and allows the binocular or scope to be moved up/down and side to side.


We supply columns is two lengths 23cm (short ) and 45cm (long)


All the Olivon heads will fit, though for a hide clamp the most useful or the TRH-11 and TRB-14. If you wish to buy a reay to use hide clamp we suggest clamp+ column L + TRH-11 head or for the more adventurous users clamp + column L + TRB-14 head. Most of our stockists will be be able to supply these eady to use.


More information about the OLivon Hide-clamp, click here


If you already have an Olivon TR-154 or TR-159 tripod, then your centre column and head can be used and you only require the clamp section.


12/ You list a large range of eyepieces and accessories for astronomical telescopes, but I don't see many actual  astro telescopes in your listing - do you make any  ?


Actually, we do make quite a lot of astronomical scopes ranging from beginners models to highly specialised instruments. Mostly though these are built to special order for our dealers. Up until now ( answering this question Nov2009 ) we've not made many astronomical telescopes for normal stock holding because of the huge amount of space required for these products. Optical Hardware however is a growing business and we now have morewarehousing available so expect to see many more models in our standard production catalogue over the next year.

We introduced 2 models into the Visionary range  there are now 105 and 114 models on the Olivon range and we've introduced 4 telescopes into the Ostara range already which are available from good stockists.

go to our astronomy page

13/ What does coating, FC,  MC, FMC and phase coating mean


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 ( multicoated ) means some of the lements have multiple layers of coating to achive better results

FMC ( fully multiocoated ) means that all the elements have multicoating

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


14/ I want to observe the sun, can I fit a sun filter to my astronomical telescope


We do not recommend a sun filter for direct observation of the sun ( though these may be useful for phography )

The sun is best observed by projection onto a screen
Important information about observing the sun and using sun filters CLICK HERE
or go to our astronomy page


15) Iíd like to see aircraft clearly at 35,000ft. Iíve tried many different binoculars and telescopes but nothing seems to work, can you help.

Itís not surprising the user had problems with this, the requirement is very difficult to achieve. Iíll 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, Youíd 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 20x60 will be better in this situation than a 20x50, 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 Ė 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, youíll 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 20x60 is fairly inexpensive, the Visionary HD 20x80 has bigger lenses and so gathers more light, quite a lot of aircraft spotters use the HD 20x80 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 itís 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

16) Is it possible to buy a telescope with enough magnification to see the moon landing relics ?


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, eyepice 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.

For a technical guide, click here guide
our more detailed technical guide, click here
For more information about night sky, astronomy and telescopes Click here


17/ How do I use an Olivon TR154 or TR159 at low level


The clips at the top of the legs release the legs to open wider allowing the tripod to sit lower.
Of course the limit is the height of the centre column because if the legs are spread almost flat then the centre column will be at it's maximum. For very low level work we make a shorter column which is available from your stockist ( see Olivon tripod section for details click here )


Another technique is to remove the centre column and replace it upside down hanging the head downwards, this is often used for macro photography


18/ Whats is the difference between a normal tripod and an equatorial mount tripod


A normal tripod will be supplied with a head designed to move side to side and up and down, this is the quickest and easiest to use for normal purposes. Equatorial mounts are designed for use with astronomical telescopes.

You can use normal tripods for astrononomy and equatorial for general viewing, but there use isn't so quick and easy.

Equatoruial mounts are designed to allow  the telescope to follow  the apparent arc movenet objects in the sky take as the earth roataes. (The earth rotates around its north/south axis, so any star which is not directly north or south will appear to move in a circle in the sky as the earth rotates)   

There are many good books and resourses on the web which cover equatorial mounts.

Click here for a basic introduction to Equatorial mounts or for more detailed information,  one of the best descriptions of setting up a mount is wriiten by Richard McDonald  http://www.themcdonalds.net/~themcdo/richard/index.php?title=Setting_Up_an_Equatorial_Mount

For general information about night sky, astronomy and telescopes Click here


19/ I'm having difficulty fitting the latiude control knob into the EQ mount on the Visionary 800/203, the polar scope seems to be in the way. What should I do ?   For more info, click here


The Polar scope eyepicee unscrews. to allow  the latitude control knob to be inserted and adjusted. It's quite a tight fit becuase the grip on the knob is quite large but it does insert much better with the eyepice removed.( we buy ready completed tripods and mounts from our factory in China, they were tested there at much lower latitudes where the large knob issue was not apparant. In case of difficulty we do now have an alternative knob. This may have been already been supplied by your dealer, if not tey should be able to obtain one for you.

For more info, click here

20) I am interested in a spotting scope for seaviews at very very large distances What range do  Visionary scopes have ?

The simple answer is that the V80 or V70 are very good for long range observation at sea but a more detailed answer is as follows :

Any telescope is capable of " seeing " all the way to the horizon, it's really a matter of how much detail can be seen at long range.This is a combination of 4 factors ;

1. The magnification of the scope
2. The light gathering of the scope ( bigger objective lenses gather more light )
3. To some degree the quality of the optics
4. The quality of air the observation is being made through,

Larger magnifications allow distant objects to appear closer, for use over very long distances magnifications of 40x to 50x can be useful, at this power something 5 miles away would appear to be only a couple of hundred metres away. The Visionary V70 and V80 have a 20x Ė 60x zoom so covers these magnifications easily.

Larger objective lenses gather more light, this means the image can appear brighter and so will be clearer.The Visionary V80 has an 80mm lens which is quite large. We also make 90mm and 100mm scopes, but 80mm is large enough for most purposes.The 90mm and 100mm versions would be better in lower light situations

More expensive telescopes usually deploy better optics which can improve resolution. Our Visionary V80ED uses low dispersion glass and with this the colour resolution is improved, but this comes at a cost, the V80ED costs more than twice the price of the standard V80. This can be an advantage for very detailed observation, but at long range the advantages of the higher quality optics are lost.

The quality of the air is one of the most important factors limiting long range viewing. Pollution, mist and heat haze seriously limit the quality of viewing. The further you try to see, the more important these factors become and viewing out to sea over a few miles usually means looking through a lot of misty hazy air. Some days are better than other but generally it doesnít matter so much how big the magnification is, how good the lenses are or how big  lens size, the viewing limit is set by the air you are looking through.

21/ I have read that my reflecting astronomical telescope needs to be collimated frequently, what do I do


Collimating simply means 'lining up' the mirrors. and most collimation adjusttments can be done easily and quickly. Like tuning a guitar, to get the best performanace, astronomical reflecting telescopes will need collimating frequently. To adjust the primary mirror, gently adjust the 3 screws on the base of the telescope.
(On some telescopes there are 6 screws, the inner screws hold the mechanism in place, gently relesae these, then adjust the mirror using the outer screws, then tighten the inner screws again ) The suggested technique is to view a bright star, defocus the scope so that the star appears like a doughnut with a dark centre. This is the reflectoion of the secondary mirror and should be in the centre. Adjust the screws until it is central. This adjustment will need to be done frequently.
If the collimation cannot be set by this method, then it suggests that the secondary mirror is  out of alignment. This  is  also done by adjusting three screws which are usually covereed by a removable cap in the centre of the holding spider. Secondary mirrors, once set, should not need adjusting very often.

For more information just pu 'collimation of a telescope' into your search engine, it is a common practice and there is vast amounts  of help already written on the web




For questions about digiscoping, click here.

Click here for our Binocular and telescope buyers guide
( note this is a large PDF file, most stockists have printed copies or contact us and we'll post you a copy )

For a technical guide, click here guide

For our more detailed technical guide, click here

For more information about night sky, astronomy and telescopes Click here

If your binocular or telescope requires a service or repair, click here


Click here for our stockists  if you donít have a stockist locally,
or canít find what you want,
give us a call


ask a question ? - click here

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