Does it make sense the image and the reticle might not be in focus because you change from a 75 yard target to 250 yds? I have noticed if I am on a low power (like 4) looking at a target 75 yards away, I can adjust the parallax knob to get both image and reticle in focus. Then if I look at a target 250 yards away on 20X power, they are not both in focus anymore. Is that because the distance has changed (75 to 250), the power has changed (4X to 20x) or both? I have a Nightforce NX8, 2.5-20, SFP scope . The parallax adjustment claims 11 yards to infinity. When I’m deer hunting, I usually set the parallax for 100 yards from sighting it in on 20 power. But when just looking at various targets while hunting (different ranges and powers) I usually just turn the side focus (parallax) knob until both the image and reticle are in focus. When I do that if I move my head up and down there is no apparent movement of the reticle on the target image. I just don’t understand the physics behind why this happens and when I would expect to need to make a change.
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Parallax adjustment ? Dependent on distance and power?
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Had your eyes checked recently? Side focus adjustment won't compensate for presbyopia or other conditions.
Are you saying that parallax is only dependent on distance? I wear correction, either glasses or contacts. And I adjusted my diopter with correction on (wearing glasses). I’m just wondering IF parallax should change when only changing zoom power and not distance? I’m not at a range to check it now. Neighborhood not good place for this. Next time at range, just want to know what to expect regarding parallax adjustment for power changes and distance .
I just did a test with my scope. I looked at an object 200 yards away on 20X power. I turned the parallax knob until both the object and the reticle were in focus. I then looked at an object 50 yards away and the image was out of focus with the reticle. That makes me think distance controls the need to parallax adjustment. I then looked at an object 50 yards away on 6X power. I focused the image with the object using the parallax knob. Without changing the distance, I then turned the zoom from 6X to 20X and they both stayed in focus. This makes me think zoom power doesn’t impact parallax much at all. So I’m thinking the dominant need for parallax adjustment is the distance you are viewing and not the power.
Yes....sort of why they put numbers on the parallax knobs. Not terribly accurate in many/most scopes but, as you said, bringing the target into clear hard focus (with the reticle already in focus from diopter adjustment of the ocular lens) should bring the target and the reticle onto the same focal plane...hence, no parallax.
And yes, you adjust parallax for differing ranges, not magnification as far as I can tell.
And since you wear corrective lenses, yes you need to set your diopter with while wearing your corrective lenses. You seem to already have done this, but this little blurb from March scopes is always helpful (obviously, ignore the first step about unlocking the diopter adjustment if you don't have a locking eye piece).
(1) Adjust the eyepiece to the proper diopter setting
The reason why you adjust the eyepiece is to set the right diopter value which differs by person and thus to see the “RETICLE” clearly and crisply. You can adjust the eyepiece before or after you mount it on your rifle, but we recommend that you do this before mounting so you can see the nearby wall or a blank sheet easier.
1. Rotate the body of eyepiece counter-clockwise until the eyepiece knurled locking knob moves freely.
2. Please set the side focus to infinity.
3. Please set at the lowest magnification setting. At lower magnification of the scope, there is more light coming in on the reticle surface. The human eye can focus more clearly when it is bright.
4. Look at a white featureless wall, a blank sheet of paper preferably at a distance of 4-8 inch (about 10-20 cm).
5. The diopter setting can be adjusted from – 2 to +2. If you are near-sighted, rotate the eyepiece body in the – direction, counter-clockwise. If you are far-sighted, rotate the eyepiece body in the + direction, clockwise. If you have prescription glasses and will be wearing them while shooting, we recommend that you adjust the eyepiece while wearing them.
6. Do not stare at the reticle for more than a few seconds while adjusting, take many quick looks as you adjust until you get the best, crispest view of the reticle.
7. When the reticle is focused for your vision, rotate the knurled locking ring counter -clockwise until it meets up with the eyepiece body to lock. Once the eyepiece is set at the best position of your vision, please do not alter the setting unless your visual acuity changes.
You can read more detailed information HERE.
Only thing power will do is amplify the fact that it wasn't in focus.
This is why on a scope that only parallaxes down to 50 yards you can still see closer if you turn down the power.
Depth of field will drastically effect it also. One scope to the next you'll see massive changes or very little. This is all setup by the optical design, and one of the trade offs of the ultra short design is very little depth of field.
Turns out the NX 8 is a short design that needs the parallax to be adjusted pretty close as it has horribly short depth of field.
What you are experiencing is perfectly normal, especially with the NX8 2.5-20. Higher magnification erectors (above 6x depending on the scope design, ultra shorts are more finicky because of their shorter focal length) tend to be more finicky than other scopes that have lower magnification erectors (6x and under). For example, you might put an ATACR 4-16 side by side with your NX8 and notice that the 4-16 is slightly more forgiving with parallax and DOF given the same magnification and distance. Also, the further out you go, the less discrepancy you will find, for example, between 250-500 will be much more forgiving than 75-250 in your example. Also, going from 11-75 will also require quite a bit of adjustment.
@Glassaholic posted the diopter procedure that I use. I have used it since I read it on the Hide. Here it is.
Diopter Adjustment from SH Glassaholic
I've adopted a method promoted by @hk dave a few years ago along with some gleaning from @koshkin that allows for "fine-tuning" of the diopter. ZCO gets the closest to getting the diopter adjusted properly in their instructions recommending you use the lowest magnification but I agree with ILya that using the lowest magnification while still being able to see the hash marks is better. Here is my latest process:
Once you’ve performed the above 4 steps you should be set with your scope, it might be wise to mark your ocular and the scope tube with a pen or marker (especially if you don’t have a locking diopter) so you can return to this position if your scope is ever bumped out of alignment.
Diopter Adjustment from SH Glassaholic
I've adopted a method promoted by @hk dave a few years ago along with some gleaning from @koshkin that allows for "fine-tuning" of the diopter. ZCO gets the closest to getting the diopter adjusted properly in their instructions recommending you use the lowest magnification but I agree with ILya that using the lowest magnification while still being able to see the hash marks is better. Here is my latest process:
- Initial setup: Set magnification to the highest setting and set side focus to infinity. Loosen the lock ring in front of the eyepiece (if it has a lock ring) and while looking at a blank wall or the sky, rotate the diopter several turns counterclockwise (in the positive + direction) until the reticle is visibly out of focus. One of the most important things is to not stare continuously through the scope. Ensure you have something distant to look at when you look away from the scope. Then glance through the scope for no more than a few seconds. Then stare out at a distant object again while making a small adjustment. Then rotate the diopter back clockwise until the reticle is focused as sharply as possible.
- Fine tuning: Find a target that is very far away, so that it looks sharpest when the side focus is at the infinity setting. As you look through the scope (important that it remains steady) you can mess with the diopter by making minute adjustments to either CW/CCW and see if the reticle and/or image improves any. You can also check parallax to ensure that small head movements don’t cause the POA to shift. When the target is in the best focus there should be no parallax movement, if there is parallax movement with a slight movement of your position behind the scope then try to fine-tune so the reticle stays locked on target with no movement.
- Closeup tuning: Now find a close target, say 100 yards away, and set your side focus until the object comes into best focus, does the reticle still look sharp? Check parallax to make sure there is no shift. Make minute adjustments to the diopter if necessary. Check back at long distances and make sure parallax and focus are still good to go.
- Final reticle adjustment: This should be done when you have nothing else to focus on within the FOV other than the reticle. Set your magnification to the lowest setting where you can still define all the hash marks of your reticle. You can either do it while pointing at a blank light-colored wall (keep the side focus at the infinity setting, so any of the minute features on the wall are blurred out) or at the blue sky. One of the most important things is to not stare continuously through the scope. Ensure you have something distant to look at when you look away from the scope. Then glance through the scope for no more than a few seconds. Then stare out at a distant object again while making small adjustments.
Once you’ve performed the above 4 steps you should be set with your scope, it might be wise to mark your ocular and the scope tube with a pen or marker (especially if you don’t have a locking diopter) so you can return to this position if your scope is ever bumped out of alignment.
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