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Paralex correction at 50 yard on quality scopes?

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/10/2009 at 15:36
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 Yes I know this question (somewhat) has been asked a million times, but not from my aspect and interest.

 I intend on purchasing a Sightron scope not that it matters in regard to the question but I am just throwing that in there.

 How much (to what degree) is a scope going to cause paralex problems relative to accuracy  in the "0 to 150yd" range? This is assuming the scope has been corrected paralex free at 50yards.

 Changeling

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/10/2009 at 21:02
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It depends on the scope and the conditions. Even scopes that are parallax-free at a certain range one day can require tweaking on another day, with different atmospheric conditions. And magnification also makes a big difference. A relatively low-powered scope will have fewer parallax problems than a higher-powered scope.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/10/2009 at 23:05
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If your eye is in the correct position with the scope there is no problem. If your hold varies when you place the firearm in position then the parallax comes into play. This is why it is important to find correct cheek weld to assist in consistent placement in line with the scope. If you are under 10 X parallax is not much of a problem until you reach at least 200 yds. depending on the size of the scopes lenses.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/11/2009 at 15:58
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 I understand atmospheric condition changes relative to optics but that has nothing to do about the question since God controls those type of conditions.
 Man on the other hand tries to do the best he can in eliminating other problems when building a scope by incorporating various techniques such as "Nothing" or adding an adjustable objective for compensation of paralex .
 
 The question was to what degree (read that as inches/parts if you like) variation can be expected from a Sightron (since you like names) in the 125 yd and under range due to paralex? My need is to get figures in inches/parts that I can use to answer my question.

 Reason for the question relates "specifically" to the need or NOT for an adjustable objective at  0 to 125 yard ranges on a scope magnification of 3 to 9/3 to 12,?  In short, how much linear variation can be expected.
  I can't think of a simpler way to put the question.

  Changeling



Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/11/2009 at 17:05
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 I'm not sure, but I doubt you could get more than an inch of worst case possible error at that distance, (trying as hard as you can to induce maximum error), before you would lose the image in the field of view.

 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/12/2009 at 13:18
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Originally posted by Changeling Changeling wrote:

 I understand atmospheric condition changes relative to optics but that has nothing to do about the question since God controls those type of conditions.
 Man on the other hand tries to do the best he can in eliminating other problems when building a scope by incorporating various techniques such as "Nothing" or adding an adjustable objective for compensation of paralex .
 
 The question was to what degree (read that as inches/parts if you like) variation can be expected from a Sightron (since you like names) in the 125 yd and under range due to paralex? My need is to get figures in inches/parts that I can use to answer my question.

 Reason for the question relates "specifically" to the need or NOT for an adjustable objective at  0 to 125 yard ranges on a scope magnification of 3 to 9/3 to 12,?  In short, how much linear variation can be expected.
  I can't think of a simpler way to put the question.

  Changeling





Atmospheric conditions have quite a bit to do with this.  The actual distance at which your scope is parallax free depends on the atmospheric conditions, as does the amount of visible parallax.  Because of that, there is really no simple answer to your question.

All scope makers try to make their scopes as well corrected for this as possible, but there are always minute errors that creep in.  In that regard no two scopes are perfectly identical regardless of the manufacturer.  If you take two scopes of the same make and model, they will exhibit slightly different parallax errors.  Whether those errors are important to you depends on what you are trying to achieve.

If you are trying to shoot the tiniest possible groups, you should get a scope with some sort of parallax adjustment.

For the typical 3-9x hunting scope from reputable makers, the parallax error is pretty small.  I seldom see more than 1MOA error for the ranges you are asking about and typically it is less than that.  If ou are looking for a precise answer, no one can give you one since this is largely a matter of scope to scope variation.  If you want to know for sure, measure it your self for your particular scope.

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/12/2009 at 17:26
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 It is surprising to me to hear JB and Koshkin explain that atmospheric conditions affect parallax. I had always thought it was strictly angular deviation caused by the eye not centered in the ocular bell, in conjunction with the reticle not being in the first focal plane (on most scopes.)
 That makes two important things I've learned today, and the sun isn't even down yet! 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/13/2009 at 15:20
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Originally posted by RONK RONK wrote:

 It is surprising to me to hear JB and Koshkin explain that atmospheric conditions affect parallax. I had always thought it was strictly angular deviation caused by the eye not centered in the ocular bell, in conjunction with the reticle not being in the first focal plane (on most scopes.)
 That makes two important things I've learned today, and the sun isn't even down yet! 


 Well, very interesting answers.

 RONK, don't get to excited about what you think you learned today! I thought this was an optics web site but to "expect" a deviation of 1MOA at 100 yard distances due to atmospheric conditions  is absolutely ridiculous.
  I'll run my own tests.



Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/13/2009 at 16:16
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Originally posted by Changeling Changeling wrote:

Originally posted by RONK RONK wrote:

 It is surprising to me to hear JB and Koshkin explain that atmospheric conditions affect parallax. I had always thought it was strictly angular deviation caused by the eye not centered in the ocular bell, in conjunction with the reticle not being in the first focal plane (on most scopes.)
 That makes two important things I've learned today, and the sun isn't even down yet! 


 Well, very interesting answers.

 RONK, don't get to excited about what you think you learned today! I thought this was an optics web site but to "expect" a deviation of 1MOA at 100 yard distances due to atmospheric conditions  is absolutely ridiculous.
  I'll run my own tests.





I did not say to "expect 1MOA".  I said that it is typically less with fixed parallax hunting scopes.  For a typical hunting rifle shot from field positions potential parallax error of up to 1MOA is essentially negligible.

If you are shooting varmints at 500 yards, or if you are shooting for groups, get a scope with adjustable parallax.

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/13/2009 at 18:49
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Changeling, your original post mentioned distances to 150 yards, not 100.
 I told you I thought it would be an inch or less, worst possible case.
Koshkin said his experience showed an moa or typically less than that.
 
If you know the answer to be something different than those estimates, why the hell did you ask in the first place?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/13/2009 at 21:58
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talking about two different things in this post, Ronk is talking about the movement on target with the head moved to one side or the other.(which would be about an inch). Changeling is talking about the parallax caused by the angle difference in two rays of light converging. The larger the objective lense the more angular parallax , (reason why small objective lense scopes don't have ao). As the dia. increases the distance between the two rays of light increases and the angle increases. The parallax in this case of say a 4.5x14 x 50 in this last case at 100 yds wil be about 2mm.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/14/2009 at 15:42
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Originally posted by Dale Clifford Dale Clifford wrote:

talking about two different things in this post, Ronk is talking about the movement on target with the head moved to one side or the other.(which would be about an inch). Changeling is talking about the parallax caused by the angle difference in two rays of light converging. The larger the objective lense the more angular parallax , (reason why small objective lense scopes don't have ao). As the dia. increases the distance between the two rays of light increases and the angle increases. The parallax in this case of say a 4.5x14 x 50 in this last case at 100 yds wil be about 2mm.


Thanks Dale, rather interesting getting an answer.
  

1 inch = 2.54 cm = 25.4 mm

2mm = 0.0797 inch

  The above is to help others with the same question.

  Changeling

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/14/2009 at 16:19
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Originally posted by Dale Clifford Dale Clifford wrote:

talking about two different things in this post, Ronk is talking about the movement on target with the head moved to one side or the other.(which would be about an inch). Changeling is talking about the parallax caused by the angle difference in two rays of light converging. The larger the objective lense the more angular parallax , (reason why small objective lense scopes don't have ao). As the dia. increases the distance between the two rays of light increases and the angle increases. The parallax in this case of say a 4.5x14 x 50 in this last case at 100 yds wil be about 2mm.


Dale, could you elaborate on this a little?  What two rays are you talking about? and what does this have to do with objective lens diameter?

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/14/2009 at 17:11
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Hello to all.
 The intention of my original question was to estimate just how much error in an average "Quality" scope could be expected in a range of 100 to 150 yards. I wasn't exactly specific about the range because, I personally didn't think it mattered (the 50 yard variance) because it should have been assumed that no one in there right mind would be looking through the scope at an angle so diverse as to be practically loosing a sight picture. Evidently I'm wrong, I think, but regardless, I asked the question that way.
  So, the logical response of the experts was to assume a worst case scenario of bending ones head from side to  side till the sight picture disappeared. I should have stated my question differently.
 If I have ruffled anyones feathers, I apologize for not being absolutely specific.

  However, the experts should have approached there responses from  more realistic directions to include both scenarios. Guys come here for buying a scope and get advise.
  Now however the average "Joe" is going to read all this and assume that he is going to loose/be off practically an inch at 100 yds because his scope doesn't have an adjustable objective. Not a lot for sticking a shot into a deer (100 yd), but see how many varminters think about your answers.

 In essence/practicality, I'm sorry I  ever asked the question. I was expecting an answer from a shooters perspective. To suggest the average to advanced shooter is going to be off at 1" to 150 yards due to atmospheric conditions without even approaching the subject of shooting form is rather amusing! 

  Changeling

  Once again, Dale, thanks for your input sir.

 I guess one could use a mirror and shoot backwards

 
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/15/2009 at 08:45
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two rays of light- one at each end of the dia. whos distance apart increases as dia. increases and also parallax.

 

change-- its very easy to be off the center of the shot-- especially in action shooting games, where the time element is considered along with the number score (called the hit factor), indeed the entire point to push these two variables until the shooter blows his score, this is called the internal clock and is different for each shooter. (IPSC uses master, A,B etc) This is one of the reasons aimpoints and EOs are used as optics for entry weapons tactics. They don't have parallax having no magnification. In precise target shooting the amount of parallax off site form the shooters frame of reference is more dependent of the gun and load used being able to print the difference in the alignment errors caused by the differences in parallax between scopes. The amt. of parallax is a factor of the scope but this small amount is increased by what ever power you are using on the variable-higher at higher mags. A really good varmit gun (or 22lr) which shoots sub moa, shows parallax errors more simply because the caliber holes are smaller and the error shows up easier. Really good precision rifles show more of clover leaf and the errors are harder to detect.

The basic  difference as seen between the two,assuming technique is correct, is one is shooting at the target and one is shooting at some place or spot on the target.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/16/2009 at 11:21
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Get Your Popcorn Ready i'm with ronk on this one---any chance i get to listen to koshkin and dale on any subject is a welcome learning experience 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/16/2009 at 12:49
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Does this help or just complicate - from Wikipedia:
 

Parallax problems result from the image from the objective not being coincident with the reticle. If the image is not coplanar with the reticle (that is the image of the objective is either in front of or behind the reticle), then putting your eye at different points behind the ocular causes the reticle crosshairs to appear to be at different points on the target. This optical effect causes parallax induced aiming errors that can make a telescopic sight user miss a small target at a distance for which the telescopic sight was not parallax adjusted.

To eliminate parallax induced aiming errors, telescopic sights can be equipped with a parallax compensation mechanism which basically consists of a movable optical element that enables the optical system to project the picture of objects at varying distances and the reticle crosshairs pictures together in exactly the same optical plane. There are two main methods to achieve this.

  • By making the objective lens of the telescopic sight adjustable so the telescopic sight can compensate parallax errors. These models are often called AO or A/O models, for adjustable objective.
  • By making an internal lens in the internal optical groups mounted somewhere in front of the reticle plane adjustable so the telescopic sight can compensate parallax errors. This method is technically more complicated to build, but generally more liked by parallax adjustable telescopic sight users—unlike AO models, which are read from the top, the sidewheel's setting can be read with minimal movement of the head. These models are often called side focus or sidewheel models[6].

Most telescopic sights lack parallax compensation because they can perform very acceptably without this refinement. Telescopic sights manufacturers adjust these scopes at a distance that best suits their intended usage. Typical standard factory parallax adjustment distances for hunting telescopic sights are 100 yd or 100 m to make them suited for hunting shots that rarely exceed 300 yd/m. Some target and military style telescopic sights without parallax compensation may be adjusted to be parallax free at ranges up to 300 yd/m to make them better suited for aiming at longer ranges[7]. Scopes for rimfires, shotguns, and muzzleloaders will have shorter parallax settings, commonly 50 yd/m[8] for rimfire scopes and 100 yd/m[9] for shotguns and muzzleloaders. Scopes for airguns are very often found with adjustable parallax, usually in the form of an adjustable objective, or AO. These may adjust down as far as 3 yards (2.74 m)[10].

The reason why scopes intended for short range use are often equipped with parallax compensation is that at short range (and at high magnification) parallax errors become more noticeable. A typical scope objective has a focal length of 100 mm. An optical ideal 10x scope in this example has been perfectly parallax corrected at 1000 m and functions flawlessly at that distance. If the same scope is used at 100 m the target-picture would be projected (1000 m / 100 m) / 100 mm = 0.1 mm behind the reticle plain. At 10x magnification the error would be 10 * 0.1 mm = 1 mm at the ocular. If the same scope was used at 10 m the target-picture would be (1000 m / 10 m) / 100 mm = 1 mm projected behind the reticle plain. When 10x magnified the error would be 10 mm at the ocular.

Another good resource to long to post here by Paul Coburn:


Edited by Dogger - April/16/2009 at 14:28
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/16/2009 at 13:24
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Originally posted by Dale Clifford Dale Clifford wrote:

two rays of light- one at each end of the dia. whos distance apart increases as dia. increases and also parallax.

 

change-- its very easy to be off the center of the shot-- especially in action shooting games, where the time element is considered along with the number score (called the hit factor), indeed the entire point to push these two variables until the shooter blows his score, this is called the internal clock and is different for each shooter. (IPSC uses master, A,B etc) This is one of the reasons aimpoints and EOs are used as optics for entry weapons tactics. They don't have parallax having no magnification. In precise target shooting the amount of parallax off site form the shooters frame of reference is more dependent of the gun and load used being able to print the difference in the alignment errors caused by the differences in parallax between scopes. The amt. of parallax is a factor of the scope but this small amount is increased by what ever power you are using on the variable-higher at higher mags. A really good varmit gun (or 22lr) which shoots sub moa, shows parallax errors more simply because the caliber holes are smaller and the error shows up easier. Really good precision rifles show more of clover leaf and the errors are harder to detect.

The basic  difference as seen between the two,assuming technique is correct, is one is shooting at the target and one is shooting at some place or spot on the target.



Dale, I am still struggling with how the two rays you are talking about make a difference especially when shooting at a comparatively flat target.  It could, conceivably, make a difference if the exit pupil is much larger than the eye pupil, but that is not an especially likely situation, I think.  How did you come up with the 2mm number? can you make a schematic of what you are talking about?

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/17/2009 at 09:18
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I wish this web site would up load mathml or worksheets in other formats but it doesn't , as it could be used to show many things from burning indexs (not some chart but the thermodynamics behind it) the method follows the explanation gave by dogger, which in that example uses the same scope set at different parallaxs, instead of different objectives sizes set at the same distance measurement.  the exact figure for the zeiss scope I got from Zeiss also their explanation about larger objective lens giving more  error . It also comes from the lens and elements design in camera macro lens which a lot use 3 element "floating" middle element to correct for this problem which becomes important in getting a 1:1 reproduction ratio.

the comparison among larger objective lenses is made from the point of view same manufacture and basically same design criteria. Of course the physical implementation varies across makers. basically the converging angle is larger -- the larger the dia.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/17/2009 at 13:20
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Originally posted by Dale Clifford Dale Clifford wrote:

I wish this web site would up load mathml or worksheets in other formats but it doesn't , as it could be used to show many things from burning indexs (not some chart but the thermodynamics behind it) the method follows the explanation gave by dogger, which in that example uses the same scope set at different parallaxs, instead of different objectives sizes set at the same distance measurement.  the exact figure for the zeiss scope I got from Zeiss also their explanation about larger objective lens giving more  error . It also comes from the lens and elements design in camera macro lens which a lot use 3 element "floating" middle element to correct for this problem which becomes important in getting a 1:1 reproduction ratio.

the comparison among larger objective lenses is made from the point of view same manufacture and basically same design criteria. Of course the physical implementation varies across makers. basically the converging angle is larger -- the larger the dia.


Dale, you are confusing the hell out of me.  What burning indexes? What does that have to do with parallax? Why would you want to burn an index of any sort? what does thermodynamics have to do with the question in hand?  What do macro lenses in cameras have to do with this (they are usually of very different design from riflescopes)?

The explanation given by dogger is the classic explanation of parallax problem in rifle scopes: image reconstructed by the objective lens system is not in the exact same plane as the reticle.  That has nothing to do with the lens diameter.

If you are talking about the converging angle of the objective lens system being larger (i.e. low F/# system that I referred to earlier), then the only reasonable explanation (aside from color issues) I can think of for induced parallax is when spherical aberrations are not properly corrected and image edges are focused in a different spot.  If that is the condition you are referring to, then the error would not be between the two opposing edges of the objective, but rather between the edge and the center of the lens.

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/17/2009 at 17:37
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  I was really going to leave this alone, but there has been so much BS/rhetoric  I have to reply!
   First off, it's mandatory that you read the entire question before you speak,  so you don't look like a fool!

 THIS QUESTION WILL POSSIBLY VARY FROM THE ORIGINAL QUESTION:  This is so you don't try to diverge the question and again look foolish, it's like a reading test!

  Lets try this another way (for an answer), being very specific about distances, proper shooting techniques and cheek weld! What this means is you know how to shoot a darn   rifle.
  You must also be able to  respond in an adult fashion. If you aren't capable of answering the question in a give or take position then you are NOT able to read!  Very simple requirements.

  The following is for a 22 caliber rimfire rifle, not a 220 swift/22-250 or any other 22 caliber, Oh, not a magnum either!

 A. Velocity 1129 feet per second (sub sonic)
 B. Bullet weight 40gr.
 C. Oh, lets say it's 85 degrees, absolutely no wind , it's  a beautiful day no clouds and the elevation is 800 ft .

 D.You are shooting from absolutely the best rifle rest that can be made, you be DA man. No one has EVER shot a better group than you!

  Question: What would be the difference/variance in impact between a scope with an adjustable objective  from "0" to "150" yards set correctly.

  VS

 A scope that does NOT have an adjustable objective set paralex free at 100 yd?


 Changeling


 
 
 
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 2 millimeters. 
 
   Say What
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/17/2009 at 20:40
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Originally posted by Changeling Changeling wrote:


  I was really going to leave this alone, but there has been so much BS/rhetoric  I have to reply!
   First off, it's mandatory that you read the entire question before you speak,  so you don't look like a fool!

 THIS QUESTION WILL POSSIBLY VARY FROM THE ORIGINAL QUESTION:  This is so you don't try to diverge the question and again look foolish, it's like a reading test!

  Lets try this another way (for an answer), being very specific about distances, proper shooting techniques and cheek weld! What this means is you know how to shoot a darn   rifle.
  You must also be able to  respond in an adult fashion. If you aren't capable of answering the question in a give or take position then you are NOT able to read!  Very simple requirements.

  The following is for a 22 caliber rimfire rifle, not a 220 swift/22-250 or any other 22 caliber, Oh, not a magnum either!

 A. Velocity 1129 feet per second (sub sonic)
 B. Bullet weight 40gr.
 C. Oh, lets say it's 85 degrees, absolutely no wind , it's  a beautiful day no clouds and the elevation is 800 ft .

 D.You are shooting from absolutely the best rifle rest that can be made, you be DA man. No one has EVER shot a better group than you!

  Question: What would be the difference/variance in impact between a scope with an adjustable objective  from "0" to "150" yards set correctly.

  VS

 A scope that does NOT have an adjustable objective set paralex free at 100 yd?


 Changeling


 
 
 


Since you have already succeeded in looking like an asshole, I suppose I do not mind looking like a fool.

You do not deserve an answer, but I will give it one more shot for the benefit of the forum (Dogger, this one is for youBig Smile as an apology for dumping a bunch of unprocessed photos on you).

You left out what the position of your eye behind the scope is and whether it varies. 

If your eye is exactly where it should be: right in the center of the exit pupil, there will be no difference.  The point of impact will be the same.

If you allow your eye to wander behind the scope then the maximum possible parallax error will depend on the specifics of the scope: focal length of the objective system and the F/# of the system (hyperfocal distance of the objective is directly proportional to the square of the focal length and inversely proportional to the F/#).

It will also depend on the exit pupil of the scope at a given setting (magnification and objective lens) and on the diameter of your eye pupil.  The combination of the exit pupil of the scope and your eye pupil diameter determines how far off the viewing axis you can place your eye.

I know you really want a concrete answer, but unless you know the specifics of your scope, one does not exist.

As for the formulation of your question, in practical terms, unless you specifically measure it, you have no bloody clue at which distance your fixed focus scope is totally parallax free.

Now on to the straight geometrical parallax that Dale was talking about.
Assuming an infinitely small observer positioned at opposing edges of the objective lens, we can calculate the parallax error for a focus distance of 100yards and target distance varying from 25 to 300yards.  Unfortunately, the absolute number for parallax error you get with this calculation is absolutely useless.  The only useful information you can glean out of this is the relative parallax error of different objective lenses.  For example, if you measured the actual parallax error with a 40mm objective scope, you can estimate what the parallax error of a larger diameter scope would be with all else being equal.


The problem with only looking at the objective lens comes from the fact that both the depth of focus and the focal differences in image location are not linear with object distance.

Changeling, for the man of your overpowering intellect, I am sure it is a simple task to measure the actual parallax error of your scope and estimate the rest.

Now, I am done with this thread.
ILya


Edited by koshkin - April/17/2009 at 22:40
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RONK View Drop Down
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 Koshkin-that was awesome!

Instead of walking him through the problem, though, you should have just baffled him with all kinds of made-up facts and figures, given him an erroneous 'concrete' answer, and let him flunk his term paper or whatever the hell he's working on!
 
 You are far too generous with your talents, IMHO.
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/17/2009 at 22:27
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MR KOSHKINExcellent If your eye is exactly where it should be: right in the center of the exit pupil, there will be no difference.  The point of impact will be the same

Edited by medic52 - April/17/2009 at 22:29
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