Parallax

[Sunspot]

At what point do you need parallax adjustment on your scope? Is it based on quality, power or both?

 

[Matt Cashell]

At what point do you need parallax adjustment on your scope? Is it based on quality, power or both?

For what use? Big game? varmint? Target? What ranges?

Parallax error is smaller than most people think. Plus of course, there is zero parallax error if you have your eye perfectly centered behind the scope regardless of parallax setting.

 

[Sunspot]

Hunting

 

[Matt Cashell]

Maximum parallax error is not based on magnification. Although it is easier to generate parallax error at higher magnifications, due to the smaller exit pupil.

The formula for calculating maximum parallax error is :

Maximum PE = 0.5D (ABS(t-p))/p

D = Diameter of objective
t = target distance (in yards)
p = parallax-free distance setting (in yards)

The resulting maximum PE will be in mm.

So to see the maximum parallax error at 600 yards for a 4-16X50 scope with the parallax adjustment set to eliminate parallax error at 100 yards:

Maximum PE = 0.5(50) (ABS(600-100))/100

Maximum PE = 125mm or about 4.92 inches.

Now that is the MAXIMUM error, so that would be with your eye lined up at the very extreme edge of the exit pupil. The error diminishes as your eye goes to the center axis of the scope, and is eliminated at the center.

The point to all this is that parallax error is not as big of a problem for long range hunting as many shooters think.

 

[Shrek]

Thanks BB . It's sometimes easy to loose prospective of the real world effects of things like parallax as it applies to hunting versus target competition. I was about to pull the trigger on a scope with parallax adjustment but it's a lot heavier and more expensive than I wanted. I'm going to have to really think it through again. The z3 4-12×50 BRH is looking good again.

 

[Matt Cashell]

Thanks BB . It's sometimes easy to loose prospective of the real world effects of things like parallax as it applies to hunting versus target competition. I was about to pull the trigger on a scope with parallax adjustment but it's a lot heavier and more expensive than I wanted. I'm going to have to really think it through again. The z3 4-12×50 BRH is looking good again.

The BRH has even less PE at 600 yards, since the scope is parallax error corrected at 200m for this very reason (Zeiss Conquest non-PA Rapid-Z scopes are corrected at 300 yards).

However, the catch with the BRH scopes is there is PE at 100 yards, so when you are doing load development, you must be disciplined in keeping your eye centered ... or do your load development closer to 200m.

 

[Shrek]

BB ! where are you getting your spec's from ? I was just on Swarovski's website and it list parallax free at 100m for 4-12×50 z3. I see the same thing listed for the zeiss 3.5-10×50 z-800 also. If your parallax numbers are right then it seals it for me skipping the parallax adjustable scope. Then the decision is between the zeiss at $500 or a demo Swarovski at $850. Any advice ? The BRH or the z800 ? I'm sure either magnification range will keep me happy on elk and mule deer to 600 yards. Thats my self imposed limit in the field as I have no wind calling experience and correction really starts to get big past 600 yards. Maybe if it was still and I was really solid I would send one on an animal longer but I would have to be really comfortable to take a longer shot.

 

[Shrek]

Actually BB , I have narrowed it down to three scopes. A zeiss 4.5-14×50 z800 @ $700 , a Swarovski 4-12×50 z3 BRH demo @ $850 , and a zeiss 3.5-10×50 z800 @$500. I'm tight for cash and the 3.5-10×50 z800 is really calling to me but the others are too. I had just about settled on the big zeiss until I got my prospective back on parallax. Anything you would add ? It's going on my 7mm wsm and it needs to go on soon so I can work up some loads.

 

[Sunspot]

I don't really understand what is gained going to a 50mm when your eye can only benefit so much over a 40-44mm. Then you have to use higher rings which will affect your cheek weld w/o a modification on that end.

 

[Sunspot]

Thanks for the input BB.

 

[Matt Cashell]

Dave,

The BRX/BRH models are parallax corrected at 200m according to the manual:

http://aa.swarovskioptik.com/download/pdf/Manuals_Z3-Z5.pdf

And the 300 yard Rapid Z setting can be found here (page 5):

http://www.zeissrapidz.com/Resource/PDF/UserManual.pdf



Both Zeiss and Swarovski note the non-ballistic reticle versions of these scopes are parallax corrected at 100 yards.

Of your choices, I really prefer the Swarovski over the Zeiss options. It can be a PITA to find your exact magnification setting for your load and the Rapid Z, but you just turn the ring all the way up on the BRH, and it is correctly subtended in MILs.

 

[Matt Cashell]

I don't really understand what is gained going to a 50mm when your eye can only benefit so much over a 40-44mm. Then you have to use higher rings which will affect your cheek weld w/o a modification on that end.

The 50mm objective gains you brightness at higher magnification settings and (at least theoretically) slightly higher resolution potential.

 

[Shrek]

Light gathering at the last legal light in shady places. If they weren't so big and heavy I would be using a 30mm tube and a 56mm objective. I have never had my sight picture too bright and clear but I have struggled with too dark and murky.

 

[Shrek]

Thanks BB , I already knew the swarovski was where I was heading due to just the thing you alluded to. The straight mils calculations would be much easier to keep track of. Input the information in my phone and it comes out with an easy match. I will just have to bite the bullet and squeeze out some more turnip blood.