Rifle Scopes Does being in middle of adj. range matter?

[pdogsbeware]

Forgive me if I don't know the correct terms for this, but you'll figure out what I'm trying to say. I'm just curious about it, that's all.

Does being in the middle of the adjustment range make for better optical qualities of a scope?

Random example. Say a scope has 50 MOA total adjustment. Would having the scope at, say 4 or 5 moa from either the top or bottom of the adjustment range make any difference in the image quality? How bout 2 or 3?

Let me know if I need to explain it more. But this is the image I get in my head when I think about the erector tube being at it's limit. I can think of reasons for it both deteriorating the image quality and not. But, I also know jack shit about the internal workings of a rifle scope haha.

 

[RSA-Raven]

Re: Does being in middle of adj. range matter?

You are correct in that there is a loss of consistency if one moves to the edge. Optical density varies & blurring or warp or combination may occur. The higher the magnification the more pronounced this becomes.
Apart from possibly not getting the correct measurements from your mill-dots, the quality might degrade at lower light conditions more than if running in middle of the parameters. Besides, this is not where the scope was designed to work…

And finally the obvious, if you need to go 5 mills more in a direction & only have 2 available, it’s an issue… Remember when elevation is maxed out, so is windage, even if you are exactly in the middle of windage adjustment. You have a tube inside another tube at the maximum point. Thus lateral movement is restricted as well. (There is a thread regarding this up on SH.) when adjusting in this area your scope will move in an oval instead of a box using box-test)
~imagine the picture you drew, but viewed from fron or rear of the tube~



I'll wager my Lunch-Sandwiches on saying all above ought to be less pronounced in high-end scopes, but still valid…
Hope I understood your question correctly…
Rgds

R-Raven

 

[bruce_ventura]

Re: Does being in middle of adj. range matter?

Off-axis optical aberrations (coma, astigmatism, chromatic) are incompletely corrected in all scopes. These aberrations increase with increasing incidence angle. You'll see the best resolution when the reticle is close to the mechanical center in either FFP or SFP scopes. Keep the reticle adjustment (from the mechanical center) within 25% of the total field of view and you should be OK. That means mounting the scope boresighted to the rifle bore correctly from the beginning, or using a biased base (10-30 moa) for long range shooting.

 

[Clark]

Re: Does being in middle of adj. range matter?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bruce_ventura</div><div class="ubbcode-body">..coma.. </div></div>
Are we going to be tested on this?

 

[pdogsbeware]

Re: Does being in middle of adj. range matter?

Awesome! Answers from people who actually know what they are talking about! Thanks guys. I really was expecting to get a bunch of smartass/retarded replies that did not even address my question.

 

[YAOG]

Re: Does being in middle of adj. range matter?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pdogsbeware</div><div class="ubbcode-body">Forgive me if I don't know the correct terms for this, but you'll figure out what I'm trying to say. I'm just curious about it, that's all.

Does being in the middle of the adjustment range make for better optical qualities of a scope?

Random example. Say a scope has 50 MOA total adjustment. Would having the scope at, say 4 or 5 moa from either the top or bottom of the adjustment range make any difference in the image quality? How bout 2 or 3?

Let me know if I need to explain it more. But this is the image I get in my head when I think about the erector tube being at it's limit. I can think of reasons for it both deteriorating the image quality and not. But, I also know jack shit about the internal workings of a rifle scope haha.

</div></div>

Ideally it is better to be in the optical and mechanical center of the scope. For most long range shooting 800-2000m (this of course varies by cartridge type) you will need a canted base even with an upper end scope with plenty of elevation range to stay in the sweet spot optically and mechanically.

HTH!

 

[George63]

Re: Does being in middle of adj. range matter?

the other advantage to setting up the rifle/base/scope to be at mechanical center for the distance where it will be used the most is windage adjustment. if you are at the top or bottom of elevation adjustment, the windage will have very little adjustment