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Frequently Asked Questions
— Riflescopes
— Binoculars
Lynx Frequently asked Questions — Riflescopes
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Q My friend says I should insist on a "multi-coated"
riflescope. What does this mean?
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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.
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- Q Should I buy a low-power or high-power scope?
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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.
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- Q Please tell me something about "variable power"
scopes
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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!).
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- Q I've had problems mounting my scope
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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.
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- Q Lynx offer a range of reticles - which do you
recommend?
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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.
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- Q Can you offer any advice on hunting dangerous
game?
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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.
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- Q What about hunting at night?
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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.
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- Q Can I correct parallax errors?
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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.
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- Q My scope seems out of focus
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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.
Lynx Frequently asked Questions — Binoculars
- Q How wide is a "wide-angle" binocular?
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A If the angular field of view of a binocular is greater that the
result given by dividing the binocular's magnification into 65, then
that binocular is considered to be wide angle. Wide angle binoculars
let the viewer see more side-to-side than regular binoculars. This can
be of great benefit in many situations, and invaluable in others.
Beneficial for bird-watching, game-watching and sport-watching, and most
other use.
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:
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9º or greater coverage, equivalent to 158m field of view or more at
1000m distance.
8 Power wide-angle binocular:
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8º or greater coverage, equivalent to 140m field of view or more at
1000m distance.
10 Power wide-angle binocular:
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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!
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- Q I'm looking for small binoculars - what should I
look for?
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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.
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- Q Which are the most popular models?
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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.
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- Q I find binoculars very difficult to see through?
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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.
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