How to use scope with parallax adjustment?

[Ccrider]

The parallax adjustment want hamper your hunting. Even if it’s not exactly correct, you will be able to see and shoot fine.

 

[Dusty Stevens]

If we’re not too far into the ditch just yet, the OP can think of it as a focus knob.

 

[drover]

I bought a tikka t3x 270wsm, I have a Burris fullfield E1 that I never used , looking to save money and put it on my tikka , it has the parallax adjustment , 50,100,200 etc yards , I have a somewhat understanding of it but never used it or a scope with it , I’m only looking to hunt with this scope/gun , so my question is , can I zero my rifle at 100 yards with parallax at 100, and then take a shot at 50-200 yards (200 yards is max I’ll ever be able to shoot where I hunt) and never have to adjust the parallax knob ?

The simple answer is - Yes. For a hunting scope what you want to do will work just fine.

drover

 

[jelenko]

To answer directly your question, the answer is "Yes, for hunting deer sized quarry, you can set parallax at 100 yards and have confidence that the shot will go where you are pointing the rifle".
The formula for the maximum error due to parallax is
Maximum PE = 0.5 (D) (t-p)/p Maximum PE is the the max error for one shot. If you took one shot with your eye all the way to one side and the next all the way to the other side, the 'error' between the two shots is twice this amount
D is the diameter of the objective; t is the distance to the target and p is the
distance at which parallax is set.

So, for a scope with a 50mm objective that is set for zero parallax at 100 yards, the max error for one shot is 12.2mm or ~ 1/2" at for shots taken at either 50 yards or 200 yards. The closer the target is to 100 yards the less the error due to parallax will be.

 

[wedgy]

When adjusting the eyepiece for reticle clarity be sure to turn the scope to max power and parallax to infinity, then point it at the sky to adjust.

 

[M-61]

I have often wondered about this ,I have adjusted scopes to the clearest I can get them and the reticle will still move while moving my eye side to side and up and down? Is this just in cheap scopes?

The clear reticle shows the focus is adjusted perfectly for your eyes.
The reticle moving while moving your eye is a parallax problem.
As I said scopes without a parallax adjuster are generally set at the factory to be parallax free at about 150 yards. Other than that there will be parallax.
As was told to me many years ago parallax can be your friend, at least in driving a car. With you driving and your wife in the passenger seat you are going 80 MPH. Your wife looks over and the speedo (to her) reads 60 MPH. That's parallax keeping the peace.
Of course now with digital Speedos and analog gone so is that example.

 

[Rem06]

The simple answer is - Yes. For a hunting scope what you want to do will work just fine.

drover

just my OCD kicking in

 

[Turbulent Turtle]

I bought a tikka t3x 270wsm, I have a Burris fullfield E1 that I never used , looking to save money and put it on my tikka , it has the parallax adjustment , 50,100,200 etc yards , I have a somewhat understanding of it but never used it or a scope with it , I’m only looking to hunt with this scope/gun , so my question is , can I zero my rifle at 100 yards with parallax at 100, and then take a shot at 50-200 yards (200 yards is max I’ll ever be able to shoot where I hunt) and never have to adjust the parallax knob ? I’m wondering if I should just buy another scope without parallax , unless I’ll be ok with not adjusting it for shooting 50-200 yards , any help or tips appreciated

The parallax adjustment, as you call it, is in fact the side focus. Its purpose is to focus the image of your target onto the first focal plane. The eyepiece is focused on the second focal plane and the diopter adjustment of the eyepiece acts exactly like ordinary glasses do and adjusts the eyepiece to your eye.

In a riflescope without a side focus (SF) or adjustable objective (AO) the manufacturer sets the focus of the objective group at distance something like 100-150 yards and then relies of the depth of field (DOF) to have the image of the target in decent enough focus from something like 50 yards to infinity. This works well with scopes that have a low minimum magnification and smaller objectives. (A rimfire scope has its focus set at 60 to 75 yards.) However, there will be parallax error if your target is at 200 yards or some other distance from the focus distance set by the manufacturer. It's small with low minimum magnification scopes with medium or smaller objectives.

Parallax error is an artifact that is generated when the image of the target is not focused on the first focal plane. So, let's say your target is 100 yards away but your side focus adjustment is elsewhere. You will notice that your target is not in focus in the eyepiece and so you adjust the side focus until you get a nice crisp image of your target. In a properly built riflescope, the image of the target and reticle will remain as is regardless of how much you move your head around when the image of the target is in perfect focus.

Now the erector set, which starts at the first focal plane and ends at the second focal plane simply transmits and enlarges the image of the FFP to the SFP. If the scope is has its reticle in the second focal plane, it will be merged into the enlarged image at that point. The eyepiece will then transmits the image of the SFP to your eye.

If you are only ever going to shoot between 50 and 200 yards you can certainly leave the side focus set to get a crisp image of the target at 100 yards and let the DOF take care of it. There will be some parallax error, but it won't be much.

I will say though, that it is easy to focus the image at 200 yards, if you have the time, and that makes it easier to hold on target and it will reduce the parallax error for that shot, and maybe eliminate it completely.

There are cases when the riflescope is defective so that when you have a perfectly focused image of your target , you can still detect some parallax error. That is usually due to the erector assembly lenses not properly focused on the FFP.

Just so you know, the side focus knob moves a lens back and forth a very small amount; this lens is s short distance in front of the FFP. An adjustable objective lens is rotated at the front of the objective bell and and it controls the distance between the objective lens elements. It's a simpler system than the side focus and does not need that extra lens .