Lynx Frequently asked Questions — Riflescopes
|My friend says I should insist on a "multi-coated" riflescope. What is it?|
|Should I buy a low-power or high-power scope?|
|Please tell me something about "variable power" scopes|
|I've had problems mounting my scope|
|Lynx offer a range of reticles - which do you recommend?|
|Can you offer any advice on hunting dangerous game?|
|What about hunting at night?|
|Can I correct parallax errors?|
|My scope seems out of focus|
Lynx Frequently asked Questions — Binoculars
|How wide is a "wide-angle" binocular?|
|I'm looking for small binoculars - what should I look for?|
|Which are the most popular models?|
|I find binoculars very difficult to see through?|
Q My friend says I should insist on a "multi-coated"
riflescope. What does this mean?
A Those who know how important lens coating is to riflescope performance are often interested to know how coating works. When light enters and exits glass, a lens for instance, about 4% is reflected away at each surface. By coating the lens surfaces with one of several suitable metallic oxides and fluorides to a critical microscopic thickness the reflections can be reduced considerably. This process, termed destructive interference, works by phase shifting the reflected light rays (putting them out of step with the incoming light rays) thereby killing the reflections by converting them to another form of energy.
A typical riflescope has about twelve lens surfaces which, if uncoated or partially coated, would produce a degraded low-contrast image due to inter-lens reflections. Coating could be expected to improve total transmission from 60% plus to 80% plus of the light entering the system. Multi-coating is a further refinement, involving the use of several coating materials which are applied selectively to lens elements in a riflescope or binocular to optimise light transmission to about 90% and balance image colour - and for specialised equipment to shift image colour to suit the human eye’s greatest sensitivity region. The effect of high grade multi-coated optics is seen in the crystal clear colour true images of Lynx Professional and Twilight series riflescopes. They give the hunter every advantage in good light and in poor light and when aiming towards the rising or setting sun.
Q Should I buy a low-power or high-power scope?
A When choosing a new scope remember that low-power models give the wide field of view necessary for close range hunting, i.e. bushveld - and that six-power or stronger is needed for the open veld. Variable-power scopes let you choose the best magnification and field of view for widely varying situations.
A Choosing the most suitable hunting scope has to do with where you hunt. Bushveld hunting calls for low-power scopes because low powers have wide fields of view, allowing the hunter to locate a close-range game animal in the scope instantaneously instead of wasting time searching for it in a higher power scope. 4x may be considered the highest useable magnification for bushy areas, and lower powers are better. Open veld hunting requires more magnification and although some hunters get by with 4x scopes they’d be better off with 6x or 8x for long-range accuracy.
Variable power riflescopes are the versatile ones giving the one-gun hunter comfortable shooting in a variety of conditions. If bushveld hunting is more important than open country, choose a variable with the lowest low-end magnification — 1.5x or 2x (in the Lynx range this would be P1.5-6x42 or 2-7x32DW models). When open country hunting predominates, variables with 9x or 10x at the top end are good choices. A useful rule of thumb is to rate every 100 metres of range as requiring 2x scope magnification e.g. 200m = 4x, 300m =6x, 400m = 8x.
Q Please tell me something about "variable power" scopes
A Variable power riflescopes give the hunter obvious advantages in being adjustable to suit changing field conditions like widening the field of view for rapid acquisition of close range targets or increasing magnification for distant targets and smaller game. Apart from moderate extra cost the modern high grade variables owe nothing to the fixed power models in that they are just as accurate, hard wearing and reliable as non-variables. When bushveld is the main hunting domain choose variables with the widest field of view such as Lynx P1.25~4x26, P1.5~6x42, 1.75~5x20, P2.5~7x28 Compact and 2~7x32. When open country hunting predominates choose scopes with 9x or 10x at their top end, like Lynx 3~9x40; P3~9x42; T3~9x44 or T3.5~10x50 . August 1999
A Hunters know that variable-power riflescopes are the best choice for general hunting in a variety of environments, but other useful features of the variable scope are often overlooked. For example, the most popular variable scope (3-9x40) produces the best target visibility at 8x magnification in dawn / dusk light, while in starry-night conditions it is at it’s best at approximately 5.7x magnification; at these magnifications, the scope’s exit pupil is approximately the same size as the shooter’s eye pupil in the light conditions mentioned, 5mm and 7mm respectively, which produces optimum illumination at the retina.
The components that make all the changes in magnification, field of view and exit pupil size are two mobile lenses in the scope’s erector tube which move backward and forward as shown in the illustrations. In variable riflescopes which do not enlarge the crosshairs simultaneously with target magnification these mobile lenses must track precisely on the scope’s axis (optical centre dotted line in the illustrations) to ensure that the scope’s aimpoint stays unchanged throughout the zooming range. Lynx variable scopes are renowned for their accuracy in this respect and for their stability under long-term recoil shocks.
A If a riflescope is pointed towards the light and held at arms-length its exit pupil shows as a bright round disc in the eyepiece. If the exit pupil is 10mm or bigger in diameter the scope is suited for fast target acquisition although at close range care is needed to centre the aiming eye to avoid parallax errors. In a variable-power scope the exit pupil changes size when the power ring is turned, giving its owner the possibility of maximising its size for various purposes - one of which is to choose the one and only magnification that will give the brightest most informative target image in low light conditions; to do this it is necessary to know that optimum light transmission to the shooter’s eye occurs when the exit pupil is the same diameter as the shooter’s eye pupil (maximum transmission matters not at all in daylight but in low light may be important).
Suppose you’re hunting in the dusk, when according to convention your eye pupil will be 5mm in diameter and you want the same size exit pupil in your 3~9x40mm riflescope to maximise its light transmission. Dividing the desired 5mm into the scope’s front lens diameter gives the power to which the scope must be set - 8X. In darker conditions you’ll use 7 instead of 5 as the divisor if you’re young enough for your pupils to dilate to that size (under 40 years!).
Q I've had problems mounting my scope
A It is not always possible to position a scope ideally on a rifle when mounting it but it pays dividends to get as near to the ideal as circumstances allow. When the rifle is shouldered and ready for triggering the shooter’s aiming eye should be aligned precisely with the scope’s axis and seeing a full sight picture without having to crane forward or ease backward. This ideal alignment of eye and scope reduces the chances of parallax errors, which occur only when the eye is off axis, and greatly facilitates target acquisition and handling comfort generally.
Lynx and other scope mount suppliers offer rings of differing heights. Select the ring height that a) lifts the scope free of obstructing the rifle bolt-handle, b) allows at least 2mm clearance between the front lens bell and the gun barrel, and c) comes closest to setting the scope’s axis in line with your aiming eye. Bear these factors in mind when buying new scopes. For instance, the eyebells of Lynx Professionals are less likely to interfere with bolt handles and the Professionals’ non-critical eye-relief gives greater freedom for positioning the scope. June 1999.
A A hunter may choose to shoot from a prone position, a kneeling position, a standing position etc. on a given hunt but it is important that his riflescope be mounted the right distance from the eye for shooting from a standing position. This places the eyepiece furthest from his eye, reducing the chances of being hit by the scope when shooting from other positions. If the scope is mounted for bench rest use, as often happens for convenience when zeroing a scope, it will be too far forward for shooting in a standing position and field of view will be sacrificed.
What's better - a two-piece or a one-piece scope mount? For most rifles two-piece steel mounts are just as "strong" as one-piece - and they are lighter and give better access to the rifle's loading port. But there are exceptions: On magnum calibre rifles a one-piece mount absorbs some of the energy that is generated by the flexing of the rifle's action under recoil, reducing strain on the riflescope. Also, on big calibre rifles where the rear mount screw holes are closer than 12mm, a one-piece mount is a better choice. Military actions which have been manufactured over several decades and by several different factories vary in tolerance and a one-piece base is sometimes preferable to two-piece by levelling out minor variations in receiver ring and bridge heights. August 1997.
Q Lynx offer a range of reticles - which do you recommend?
A As a hunting region Southern Africa is not far from being No. 1 in the world for diversity of game sorts and varieties of dangerous game animals. Yet we don't have a national riflescope crosshair design like New Zealand, Germany, Scandinavia, etc. Martiens Grobler of Big Buff Guns of Zimbabwe suggests an 'African Dangerous Game" crosshair, having unusually thick posts linked by short crosshairs of 25 micron thickness, which he considers to be an ideal scope aiming reference for use on dangerous game in good and poor light, standing or moving; the design looks like a modification of a typical European first-plane crosshair when the scope is set at its lowest power, but Mr Grobler wants the ADG crosshair to be located in the scope's second focal plane so that the crosshair doesn't change dimensions when the scope magnification changes i.e. the clear central space between the thick post ends remains the same size regardless of scope magnification and the 25 micron aiming hairs get progressively thinner relative to the size of the target image when the scope is zoomed upwards in power.
Lynx invites comments from shooters who are interested in the subject and perhaps have ideas of their own for a regional crosshair design; if there appear to be grounds for developing such an aiming graticule we would manufacture it and offer it as an option in appropriate Lynx riflescope models. Comments on the above should be in the form of a fax, letter or e-mail (not telephonic). December 1998
A Some of the responses to the Lynx offer of Nato and Mil-dot ranging graticules have made it plain that many shooters are unaware of the rangefinding features of standard Lynx crosshair graticules, which can be used for judging distances closely enough for most hunting purposes. The thin vertical line of the crosshair is the basis of the rangefinding system; this line measures 90cm on a 100 metre distant target; half of the line measures 90cm on a 200 metre distant target.
These measurements apply for 4x scope magnification and are easily recalculated for other scope magnifications. For example full grown impala rams average 90cm shoulder height (“grond tot skof”); at 100m the ram will fill the thin vertical line and at 200m he will fill half the thin vertical line; over- and under- filling of the lines translate into proportionally shorter or longer distances, in that order; approximately 10% over-fill of the 100m line is approximately 90m range. Adapting the impala parameters of 90cm=100m to suit other game animals can be done by changing the scope magnification. For springbok (75cm shoulder height) the 4x magnification is changed 90÷75 (impala÷springbok) to 4.8x (5x is near enough). The reason for using the vertical line of the crosshair is that average shoulder heights for given animals vary less than average body lengths; also, using the height avoids foreshortening due to perspective. A list of average shoulder heights for South African game animals is available from Lynx on request.
Ranging by graticule is practical at long ranges when time is likely to be less pressing and good information is needed most. There are drawbacks, including interference from atmospherics, long grass etc. but the system is continuously adaptable to suit different user techniques; for shooters who are prepared to spend time adapting the system to their needs the rangefinding facilities add value to a scope without adding to its cost.
A Mil-dot sniper graticules or crosshairs with spaced opaque dots are standard in most law enforcement riflescopes for range estimation and aiming. Nightforce have refined the mil-dot graticule by making the dots and posts see-through, so they don’t obscure target detail, and by adding extra dimensions to assist ranging small targets. At a specific magnification, which varies from one scope model to another, the see-through dots are spaced 1 milliradian apart centre to centre, which translates to 1/1000th part of the target’s distance from the shooter i.e. 100mm at 100 metres, 1 metre at 1000 metres etc. A formula provided with the riflescope adapts the mil-dot graticule for ranging twelve most common South African game. The illuminated glass etched graticule can be set to one of ten intensity settings for use in low light conditions.
Q Can you offer any advice on hunting dangerous game?
A Using quick-detachable mounts to ready a scoped rifle for use on dangerous game animals trades the aiming precision of optical sights for the safer alternative of iron sights in case a charge situation develops. Another choice is to use a low-power riflescope which allows aiming with both eyes open and doesn’t impair the shooter’s judgement of the range and approach speed of a charging animal. The latest Professional Series Lynx 1¼ - 4½ x riflescope serves this purpose, with added advantages of enough magnifying power for general bushveld hunting to about 225 metres, extended eye relief for comfortable use on big calibre rifles and an unflared body tube permitting the scope to be mounted as low as possible above the rifle barrel. The 30mm monotube scope is coded 3P 1.25-4.5x26D. November 1998.
Q What about hunting at night?
A Man and other daylight creatures have two sorts of light-sensitive receptors in their eyes — “cone” cells for colour vision and “rod” cells for low light vision. Colour doesn’t exist naturally in darkness and nocturnal animals have no need for cone cells in their eyes; instead they have light-amplifying “tapeta” membranes which give them night sight and their “cats-eyes” reflectivity turning night into day for them (and causing their eyes to reflect light like mirrors). The reactions of such colour-blind animals to powerful different-coloured spotlights at night indicate that they see the lights in different degrees of brightness — blue light being brightest and most threatening, red as dimmest and least threatening and white as dazzling and disorientating (verwarrend).
Red light is thus the best light for night shooters of nocturnal pests, jackal, bushpig etc, and is also the least disturbing light for game viewing and culling of diurnals. But red filters absorb a lot of light and powerful shooting lights projecting concentrated beams over 250 metres and greater distances are needed for best results. Nightforce RMSM140 and RMSM170 scope-mounting lights are chosen by many night shooters as the brightest and lightest of the commercially available lights. Image visibility at night is considerably influenced by the best combination of riflescope light collecting capabilities and magnification. The following riflescopes are recommended to shooters wanting peak night time performance: Lynx 6x and variable power riflescopes with 42mm and 44mm front lenses, are also excellent for night shooting. September 1998.
A The two popular reference systems assisting buyers to select scopes and binoculars for use in low light and at night are Relative Brightness system and Twilight Factor system (Dämmerungsfaktor). Both systems are useful and both have anomalies to be aware of. To use the information you need to know that an instrument's exit pupil is the bright round disc of light seen in its eyepiece when it is held at arm's length - and that the diameter of the exit pupil in mm is obtained by dividing the instrument's magnification into its front lens diameter i.e. an 8x56 scope or binocular has an exit pupil 56/8 = 7mm diameter.
Relative Brightness (RB) assigns numerical ratings to binoculars and scopes e.g. 25RB for a 7x35, 50RB for a 7x50 - telling the user that a 7x50 is twice as effective as a 7x35 at night when his eye pupil is 7mm in diameter. The RB numerical ratings are the squares of the exit pupils of the two instruments concerned, i.e. 5x5 for the 7x35 and 7.1x7.1 for the 7x50. The weakness of the RB system is that it does not take into account the instrument's magnification - and magnification has a big influence on target visibility at night. For example a 6x42 and an 8x56 riflescope both have exit pupils of 7mm (RB rating 49) but the 8x56 is almost 50% more effective at night when the user's eye pupil is 7mm.
The Twilight Factor is the square root of the product of magnification and front lens diameter, i.e. for an 8x56 scope the Twilight Factor is (square root 8x56)=21.17. For a 6x42 it is 15.87. The "weakness" of the system, if indeed it can be called a weakness, is that it gives misleading results for high power, small diameter instruments - a 20 power scope with a 20mm front lens diameter has a Twilight Factor of 20 but in practice the user would see almost nothing through it at night. A user of this system must stay aware of the major importance of 5mm, 6mm and 7mm exit pupils for conditions ranging from dawn/dusk to starry darkness. May 1998.
Q Can I correct parallax errors?
A Hunters of impala-size and larger animals are seldom if ever affected by parallax errors when using normal hunting scopes on targets between about 50 metres and 200 metres, because parallax errors which may occur are too small relative to the aiming area to matter. Nevertheless it is good sense to use the lowest available scope magnification for close-range shots - sixty metres and less - because the lower the scope magnification is the smaller will be the parallax error that results when the shooting eye is off the scope’s axis.
High-power riflescopes intended for varminting and target shooting invariably have focusing facilities to eliminate parallax but such scopes are usually unsuitable for general shooting. Now Lynx are offering two medium-power variables with parallax focus, for hunters wanting an extra degree of confidence for taking long range and short range shots and for targeters and silhouette shooters not needing extreme magnifications. To complement the small hunting rifles coming onto the market Lynx have introduced a compact 2.5x~7x 28mm in the professional series. October 1998.
A A riflescope’s axis is an imaginary line running through the dead centre of the front and back lenses. When the shooters aiming eye is precisely in line with this axis he will not experience a parallax error even at distances outside the scope’s parallax-free zone, but such alignment is seldom achievable during the heat of the hunt. Parallax errors in a riflescope magnifying 8 or 9 times and more are frequent contributors towards missed shots beyond 200 metres on small targets such as a springbok heads and the like. So, largely with springbok hunters in mind Lynx is developing two normal-size focusing riflescopes for parallax-free shooting from 10 metres to about 450 metres. The scopes are fitted with finger-operated windage and elevation controls. May 1998.
Q My scope seems out of focus
A Five minutes spent re-focusing a riflescope crosshair to match your personal eyesight upgrades your shooting performance. There’s a right way to do this and some wrong ways that lead to spurious results. Loosen the scope eyebell lock ring and screw the eyebell outwards several turns, until the crosshair appears blurred; point the scope at the sky, away from the sun, or at a well-lit featureless wall if you are indoors; screw the eyebell inwards half a turn at a time until the crosshair is at its sharpest; if you go past the point of sharp focus screw out the eyebell a few turns and start again. Lock the lock ring once you are satisfied with the setting. The same procedure holds for fast-focus scopes, excepting that half a turn anti-clockwise is enough to blur the crosshair. It is important to focus by screwing the eyebell / fast focus lens from outwards to inwards, i.e. clockwise, to prevent your eye adapting to an unsharp image. If focusing is done the other way round your eye will pull the crosshair sharp prematurely, but temporarily.
Q How wide is a "wide-angle" binocular?
A Wide-angle binoculars show up to 60% more picture area than some standard models of the same power, making it easy to track fast action subjects, from wildlife on the move to the fluctuations of rugby games. The 7x and 8x wide-angle models are good choices for general purpose binoculars.
Big front lenses don’t make a binocular a wide-angle model - the optical design of the eyelenses determines the field of view - and the easy way of getting the facts is to read the information printed on the shoulder or elsewhere on the binocular which will be in angular degrees and / or linear measure e.g. 6.5º / 114 metres at 1000 metres. The rating “Wide-Angle” is assigned to binoculars with certain minimum field coverage specifications, as follows:
7 Power wide-angle binocular:
9º or greater coverage, equivalent to 158m field of view or more at 1000m distance.
8 Power wide-angle binocular:
8º or greater coverage, equivalent to 140m field of view or more at 1000m distance.
10 Power wide-angle binocular:
6.5º or greater coverage, equivalent to 114m field of view or more at 1000m distance.
(1º is equivalent to 17.5m at 1000m and 52.5 feet at 1000 yards)
The Lynx 14-7x35 extra-wide-angle binocular gives coverage of 11º (193m @ 1000m).
When purchasing binoculars check and compare their field of view, which can explain price differences between seemingly similar binoculars. All other factors being equal wide-angles will cost more!
Q I'm looking for small binoculars - what should I look for?
A Don’t expect a mini binocular to be a general purpose binocular. An optical fact of life called Dawes’ Limit restricts the ability of the mini’s 21mm objective lens to separate fine detail to a relatively low value of 5.5 arc seconds, compared with 2.3 arc seconds resolved by a 50mm diameter lens of similar quality. The 50mm lens’ resolving power is about 26 times better than that of the human eye and is a superior choice for many binocular users, while 40mm and 30mm lenses offer compromise between mini and semi-compact designs.
But the most important binocular feature is shockproof construction to keep the twin optical systems precisely aligned with one another for years of strain-free comfortable viewing. You’ll experience this all-important advantage in all 36 Lynx binocular models.
Q Which are the most popular models?
A Binoculars magnifying by 7x or 8x are the most popular types world-wide, mainly because they are easier to hold steady than those of higher magnifications, although other factors also play a part in their popularity.
However, for some activities, especially those involving wild creatures, there is sometimes need for stronger magnifications; then the variable-power "zoom" binocular can be a good substitute for two or more single-power models.
The Lynx 6-12x25 binocular, is a fine example of a zoom, combining pocketable size with excellent optical and mechanical performance and a useful power range to 6x to 12x. This and all other Lynx binoculars are built to last for years of trouble-free service without the need for over-protection.
Q I find binoculars very difficult to see through?
A A major advantage of high-grade binoculars over lesser grades is that they stay aligned and good-as-new for years of regular use without needing over-protection.
People who blame themselves for not being able to use a binocular comfortably are usually extra sensitive to the image distortions caused by imprecisely aligned optics. A quick check for the commonest alignment fault is to hold the binocular about 80mm from the eyes and look through it at a horizontal line such as a house gutter or roof top about 30 or 40 metres away; if the line appears broken - the part seen through the other eye lens - the binocular will strain the user's eyes and needs repairing.
Look for smooth, positive controls, firm bridges supporting the ocular lenses and brilliantly sharp image, and the "feel" of quality.
Lynxoptics is a Registered Trade Mark of Gault
This website is the the property of Lynxoptics©