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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/17/2010 at 05:43
Booborowie View Drop Down
Optics GrassHopper
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Parallax

Realistically how critical

First Post

From Aus, was into shooting many years ago, small game and duck/waterfowl and circumstances had me give it away.

Now by good fortune back into it.Excellent

Have a cz452 and would like a sightron 2.5 – 10 x 32 compact, looks like it will fit behind the rear sight that I don’t want to remove.

Given that I’ll be hunting small game to 75 but also silly wets to 100 how critical is parallax on a non AO scope??

Can I get away with the above scope or similar non AO given that I can compromise on eye position       ( half blind anyway Big Smile )

Cheers

 

Booborowie ( pub in the mid north of SA) 

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/17/2010 at 07:39
8shots View Drop Down
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Welcome to the OT or as you say down under G'day mate!!!
 
Do a search under rifle scopes and see this article has been well covered.
 
Firstly, most non AO scopes are set parallax free at 100 yds at the factory. So between 75 yds and 125 yds you would have virtually no error.
Secondly, at 10 x and lower power it is also considered that parallax as an error is largely ruled out due do the longer focal distance, even at shooting distances beyond 300yds..
On the bigger powers such as 20X etc the focal distance is very short and parallax error can occur.
Having said that, even at 20X and shooting at inside 300 yds, the error is probably no more then 1MOA, so even small game will not be missed as a result of parallax error.


Edited by 8shots - August/17/2010 at 07:41
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/17/2010 at 10:47
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Welcome to OPT Boo.
 
Good info 8shots.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/19/2010 at 02:49
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Originally posted by 8shots 8shots wrote:

Welcome to the OT or as you say down under G'day mate!!!
 
Do a search under rifle scopes and see this article has been well covered.
 
Firstly, most non AO scopes are set parallax free at 100 yds at the factory. So between 75 yds and 125 yds you would have virtually no error.
Secondly, at 10 x and lower power it is also considered that parallax as an error is largely ruled out due do the longer focal distance, even at shooting distances beyond 300yds..
On the bigger powers such as 20X etc the focal distance is very short and parallax error can occur.
Having said that, even at 20X and shooting at inside 300 yds, the error is probably no more then 1MOA, so even small game will not be missed as a result of parallax error.


Thanks

So at shorter distances say under 75 if I use lower powers 2 - 3 - 4 parallax wouldn't be an issue?

I don't want to limit myself to a rimfire scope  and I prefer side focus to adjustable objective, more so this reason. When I've used an ao scope it's felt awkward.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/19/2010 at 19:35
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I just bought a 4x32 Swift parallax free at 50 yards and the parallax error is as large as a small maple leaf (2inch diameter) at 35 yards.  I shoot a lot at close range so the error is too large for me and I am looking for another scope.  I am having a problem placing an order on another scope sight unseen and we don't have many dealers with a large stock to choose from.  But to answer your question, depending on the scope, close range parallax at 4x may be a significant issue.  The best way to know is getting an exact model number recommendation from a trusted source (and verify tolerance before mounting), or look at one in person.  Also, at what range do you want the scope to be parallax free?  If AO/SF, how close do you need it to focus to?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/20/2010 at 01:24
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Originally posted by robmints robmints wrote:


 Also, at what range do you want the scope to be parallax free?  If AO/SF, how close do you need it to focus to?



Minimum 25
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/20/2010 at 02:17
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@Robmints are you sure your scope is parallax free at 50 yds? How are you measuring the error?
The error you are having seems very large for a 32mm scope and only moving 15m closer then your parallax free distance.
Parallax error is a function of the objective lens. The larger the objective lens the larger the PE will be, given that the other factors remain the same.
So for a 32mm scope to show such an error something has to be off.
Your parallax error should be no more then 0.5*32* (50-35)/50= 4.8mm. Which is a lot less then 2 inches. That is from center to one edge..so total movement = 10mm or 1/2 inch.
If your parallax is actually 100m then it would be 10mm which is close to 1/2 inch. That is from center to one edge, so total from edge to edge movent will be 1 inch approx.
 
You can only have your eye off the axis to one side when aiming, so PE is half of total apparent movement observed when moving eye from side to side of optical axis.
 
Back to Booborowie, the closer you move to your target and with a large power and with a large objective, then the more critical PE becomes, hence why air rifles shooters have AO.
There is no one scope fits all.
You have to decide what you predominantly want to do and buy a scope to fit that function.
If you want to hit flies at under 75 yds, then get an AO.
If you want to hit beer cans at under 75 yds, then no AO is required.  


Edited by 8shots - August/20/2010 at 02:47
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/20/2010 at 02:24
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By the way.. the effect of the power of the scope can be used in similiar calculations, but for that you need to know how many mm offset your eye is from the axis of the scope or lenses.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/22/2010 at 18:43
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No I am not sure it is parallax free at 50.  I was doing it by guessing (well estimating really) and looking at a poplar leaf.  But I will get out the tape measure to mark off 50 and 35, and a ruler to look at.  Thank you 8shots.  I will start a new thread unless OP says it's ok to continue here.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: August/23/2010 at 03:20
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Originally posted by robmints robmints wrote:

OP says it's ok to continue here.

Go for it
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/04/2010 at 11:52
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Originally posted by 8shots 8shots wrote:

@Robmints <snip>
You can only have your eye off the axis to one side when aiming, so PE is half of total apparent movement observed when moving eye from side to side of optical axis.<snip>
So why not do what iron sight shooters do and "align your sights" (or align your eye to the scope)?  I do this by either momentarily exceeding the eye relief to produce the "tunnel shadow" (don't know what it's called, technically) or temporarily changing my cheek weld pressure to move my eye up/down and right/left to produce the shadow in the eye piece.  Your eye is centered when you center the shadow to be concentric with the eyepiece.  Keep it centered as you move it back into your normal cheek weld.

Doesn't this technique keep parallax error very small in all but very high power scopes, perhaps?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/05/2010 at 14:10
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Originally posted by calinb calinb wrote:

Originally posted by 8shots 8shots wrote:

@Robmints <snip>
You can only have your eye off the axis to one side when aiming, so PE is half of total apparent movement observed when moving eye from side to side of optical axis.<snip>
So why not do what iron sight shooters do and "align your sights" (or align your eye to the scope)?  I do this by either momentarily exceeding the eye relief to produce the "tunnel shadow" (don't know what it's called, technically) or temporarily changing my cheek weld pressure to move my eye up/down and right/left to produce the shadow in the eye piece.  Your eye is centered when you center the shadow to be concentric with the eyepiece.  Keep it centered as you move it back into your normal cheek weld.

Doesn't this technique keep parallax error very small in all but very high power scopes, perhaps?
 
This is call good consistant cheekweld and forms the basis of producing accurate shooting.
I have done some shooting excercises out to 400yds with a poor parallax setting (deliberate) and still produced accurate shots.
So yes, it can be done. As I say, the maximum parallax error is A, but this can be reduced by keeping your eye on or close to the optical axis with good cheekweld.
A rather hot debate followed as to wether this is good, bad or just plain ugly.
The whole drama is recorded under the riflescope threads.
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