A1. Two figures are used to denominate a binocular or telescope - 8x 21, or 10x 50 for example.
The first states the magnification (power) on a standardised scale. Think of this as giving an image as at eight times or ten times closer to your subject.
The second figure is the diameter of the front (objective) lens, which indicates both how much light can enter that instrument, and what sort of size the binocular or telescope will be.
A combination of three figures, 8-20x 50 for example, represents an instrument with variable power (a "zoom" binocular). In this case an instrument which can be used at any power from 8x to 20x magnification. Bear in mind the points below regarding light and width before considering a zoom binocular.
Q2. What is "Field of View" (or "Width of View")?
A2. The width of your subject in view at one time. Usually this is represented by an angle (7° is good), but sometimes defined as yards or metres width in view at 1000 yards or metres distance. The higher the magnification, in general, the narrower the field of view.
Q3. What are the benefits of a larger instrument?
A3. A larger front lens collects more light. More light gives greater definition or detail.
Q4. What are the benefits of higher magnification?
A4. The greater the magnification, the more detail on your subject you are likely to see. However, your width of field (view) will be decreased, and, if the instruments being compared are of the same physical size, the definition or clarity of your subject will be poorer because higher powers provide less light. The reduced width of field also means that your movement represents a greater proportion of the picture - you will appear to "wobble" more.
Q5. Why can I buy an instrument at £10, and one of similar size and power at over £100?
A5. Quality. As you pay more you can expect the instrument to deliver more light, in a much better state than cheaper versions. As a result the definition will be better, the colour and focal depth will improve, the instrument is probably better built, and you will suffer less eye strain with continued use.
Q6. Why are binocular lenses coated? What does multi-coating mean?
A6. It's all to do with light, how to transmit it, how retain the image's integrity.
Coatings are used in part to finish a lens off to a very smooth surface, rather than spend hours polishing the glass, but modern chemistry in different coatings also mitigates light loss at the glass surface. Multiple coatings and high quality coatings can reduce this light and colour loss quite spectacularly so enhancing the definition. If, on this website, a binocular is described as "Fully coated", this means that each glass surface is coated.
"Multi-coated" means that one or more glass surface has multiple coatings, and "Fully Multi-coated" means that all glass surfaces have multiple coatings. Much of the cost in higher value binoculars relates to the quality of coatings.
Q7. What does "waterproof" really mean?
A7. On this website, all of our binoculars are at least what we would term "Showerproof," ie they will take a little rain without damage. Other sites may well describe such instruments as waterproof, but at Far-Sighted "Waterproof" means specifically that the instrument body is sealed against water ingress. Moreover all our waterproof models are Nitrogen filled, so they start life without any moisture inside which can condense on to the internal lens surfaces. The degree of waterproofing varies. You should expect a marine pair to suffer complete submersion just below the water surface for a short time without suffering water ingress (time enough to recover it if fitted with a bouyancy strap), and a military spec to suffer several minutes of submersion to half a metre, perhaps more. All our waterproofs should stand a covering of water for a short time. Eventually the Nitrogen fill will leak out of the instrument, although their seals should retain integrity against water ingress as above, for several years.
Most waterproofs are sold so that they can be used in damp environments without much risk of misting on the inside (if you keep them on a boat, walk a lot in the wet, or carry them in a damp fishing bag, for example).
Q8. What is the Diopter (Ocular)?
A8. The eyepiece lensing.
Q9. What is the Objective?
A9. The large, front lens collecting the light from the subject image.
Q10. What is the "exit pupil"?
A10. The column of light carrying the magnified image from the Diopter to your eye. Ideally this should always be as big as the diameter to which your pupil is open (which, in reality, in good daylight, is not very large). The exit pupil can be roughly calculated by dividing the objective lens diameter by the magnification.
Q11. What is the difference between an Astroscope and a Spotting scope?
A11. Both are telescopes, enlarging distant objects to present to the observer. Spotting telescopes are prismatic, and will convert the image to be the "right" way up. These are invariably the type used for nature watching and land views, but the larger ones (80mm objectives or more) are also excellent for star-gazing.
Astroscopes in general give an un-corrected image (ie "upside down and wrong way around), their main function being to achieve high magnifications, for which they collect a lot of light. They are generally much bigger, and/or have more complex light paths to achieve the power. They are used for observation of tiny areas of sky, and the larger ones can often be fitted with motorised mounts to track the planet or celestial body over long periods.
If you are a star-gazer, not an astronomer, stick to a standard Spotting telescope. Low light binoculars and large observation binoculars are also often used for moon and star-gazing.
Q12. What is Digi-scoping?
A12. Digi-scoping is a new phenomenon amongs wildlife enthusiasts, but easy for anyone to achieve with most of our telescopes. Digi-scoping is the art of photography through your telescope, often using the telescope as the actual camera lens. Given a relatively good telescope, the right adaptors, and a digital camera, it will revolutionise your ideas on photography, at much lower cost than using telephoto lenses. Adaptors for SLR cameras connect the camera body direct to the telescope, for other cameras there are support brackets available to position your camera at the eyepiece, giving it the view that you would see.
