My answer to a request for explaining scopes . . . .
Posted 20 October 2008 - 09:03 pm
Rifle telescopes (‘scopes’ hereafter) can be very daunting and confusing things on the whole -, particularly if being looked at for the first time. Hopefully, this document will go some way towards cutting down on some (or doing away with it altogether) of the confusion that tends to confront us.
Telescopes are, essentially, a tube containing several lenses (sometimes as many as eight) some set together, and some set apart from each other within the same scope. In amongst them somewhere, is a thing called a ‘cross-hair’ or ‘reticule’ – this is what you place on your target. The very centre of the reticule should (all things being equal) dictate exactly where your pellet or bullet will strike on the actual target.
At the very front of most scopes, there is what is termed the ‘objective bell’ – this of course contains the main objective lens (the largest in the scope), while at the opposite end is what is called the ‘eye bell’ – this is the part nearest your eye when you look through the scope. All scopes will have a focus ring at the eye bell end – this is used so that you can get the reticule in the sharpest and clearest definition for your own eyesight.
Some scopes are termed ‘fixed’ magnification (mag.) – these scopes will not be able to be altered in any way, in terms of magnification power – ‘what you see is what you get’, type of thing. Then of course there are the ‘variable’ mag. scopes, these will have an adjustable magnification – anything typically from say, 3-9x for most scopes, and some scopes will go from 6-24x magnification. Each type of mag. parameter has its own uses – it is down to each of us to decide what we want of the scope we want to own.
There are scopes that have a facility where you can focus the target to the point where (like the cross hair focus ring) the target is in sharp focus, you can then read the number that lines up with an index mark on the scope itself – and this will give you the distance to the target (either in yards, or meters). Having said that, not all scopes have the adjustable focus at the objective end – there are also others that have an ‘extra’ turret on the left hand side to do the same thing. These scopes can be fitted with a wheel that fits directly onto the turret – they are known as scope wheels, and also as side wheels; these make the adjustment a bit easier to do whilst looking through the scope.
EYE BELL PARTS:
- - - - - - - Eye Lens - - - - - - - - - - - - - - - - - - - - - - - -Reticule focus - - - Magnification
- - - - - - Securing ring - - - - - - - - - - - - - - - - - - - - - - - - Lock nut - - - - - - - Ring
Focusing this scope eye bell is achieved by grasping the eye bell itself, and twisting until sharp, clear focus of the reticule is gained, and then nipping the locking nut back up against the eye bell – to finger tightness only.
The pictures above are those of my 3-9x40 Simmons riflescope; this has an adjustable magnification facility – from 3x, up to 9x power. It has adjustable reticule focus as well, by way of twisting the eye bell, and locking it in place using the focus lock ring once sharp and clear focus of the reticule has been attained.
Looking through the scope
Many people would seem to be somewhat confused as to how the image they are confronted with,
When looking through a scope, should look. This section should go some way to solving this particular quandary. If you observe the following picture, you will notice there are two separate views, which are individually notated as to what they refer to – this is the correct view, and the incorrect view through a scope.
The ‘visual field’ should look like a perfect circle containing the view of what you are looking at, and this view should fill up the whole of the eye bell – i.e. the whole thing should fill the eye bell to its edges and there should be no black areas at all. When you are at this stage, you are at what is termed to be the correct ‘eye relief’ distance. If there are black areas present, then your eye is either too close to, or too far from the eye bell itself, as is stated in the preceding picture.
This is my answer to a recent request for this type of help file on scopes, and their various bits and pieces, which i hope will help those who are not familliar with them to become so.
Posted 20 October 2008 - 09:19 pm
All the best,
Posted 20 October 2008 - 09:26 pm
the bit at the far end from the eye peice, if it moves to focus is the paralex.
the parralex 'error' can be seen if you look at your target and cross hair then very gently wiggle your head a touch, if them cross hairs wiggle off the target theres paralex error... so you focus the paralex till the image is clear, theen if you wiggle your head the cross hairs should'nt move..
the average scope with no adgustable paralex will be already paralexed at a 100 yards.. this can be changed if you know how or some one else who can, but... theres a 90+ percent nitrogen air fill that helps stop fogging and the likes, it also aids a clearer image, without the gas you'll not see much diference, but... come a dull day or twighlites the image goes grey, and/or you wont see as late into dusk..come lamping...bad image untill you crank up the watts on the lamp.(the atmosphere is 70 something percent nitrogen..NOT 90+).
the paralex error is a thing that happens because your looking through lenses, each curface refracts the light as well as reflects it.. so another lense arangement 'corrects the error'..
side issues... the coating's on the lenses help light transmition, every curface (thats two per lense) cuts light out..untill it gets a coat... heat treated(red colour) is the best, mutlticoating is next(ppinky red'ish purply), then just the green fully coated..
theres also a spec that involves the inside of the tube being coated, this stops light bouncing up and down at the bad same angle as the lense, it makes a white screan out..basicaly its as it sounds, one second your looking at a good image, the next it goes all white and you cant see any thing.
one cure is the old sun shades attached at the front.. another is the coating, boath are better...if not.. dont worry to much, it only happenes acotionaly...you'll learn not to look there.
the main body tube, its usualy a 25mm (1 inch they say) or a 30mm tube, the bigger the tube the more light can pass through and the bigger the image.. i prefer the 30mm.. but thats to my eye's liking not everyones..
beware of any one who tries to sell you you not knowing what the scope is...if they dont know you wont...till it's to late.
Edited by ghillies, 20 October 2008 - 09:28 pm.
Posted 22 October 2008 - 07:40 am
That's brilliant grim, thanks mate. I'll keep this together with your range setting post. Could I also ask if you can do an explanation of the fittings that connect the scope to the rifle. There seems to be a variety of these as well?
Posted 22 October 2008 - 09:26 am
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