Rifle Scopes Target image drifting in and out of focus

[cetanorak]

Hello folks,

Encountered a strange issue today at the range, while zeroing at 100 yards, that has me a bit stumped. The rifle shot and zeroed without issue, but I was continually battling a strange phenomenon that I have never encountered before where, while the reticle would be sharply focused (properly adjusted the diopter***) , the target would drift in and out of focus. It honestly felt kind of psychedelic and had me wondering if my eyes were suddenly going bad. It happened a little more severely when at maximum magnification power.

My first thought was suppresssor mirage-effect, as the air temperatures were 50 degrees, and I do not have a suppressor wrap. I let the barrel cool but the issue would persist. I've read about issues with overtightened scope rings hindering the operation of the parallax/AO turret, but my scope rings were torqued to 18 in/lbs and the erector performed well on a tall-target test.

Can anybody think of what would suddenly be causing such an issue? I'm not sure if I have a warranty issue emerging or if there is something that I'm overlooking.

I've been shooting my current setup for a few years without issue: Remington 700 Tactical, Vortex Viper PST 6-24x50 FFP, Seekins Scope rings and a SilencerCo Omega suppressor.

Also, I do not wear glasses.

Thanks folks!

*** diopter was adjusted as instructed in Setting up a FFP rifle scope - A simple PSA on Diopters

 

[lennyo3034]

Check your diopter. It’s probably not adjusted properly for your eyes.

 

[WilburW]

I experience that, as well.
Usually after multiple rounds.
I am not certain, but think it is due to mirage off my un-jacketed Omega...

 

[cetanorak]

If the diopter was improperly adjusted would that result in the target image shifting from in focus to out of focus, if distance, magnification and parallax adjustment are constant? I figured that if the diopter was out of adjustment, then the image would just be a fixed amount out of focus continuously, not shifting in and out of focus. But that's just my layman's assumption.

 

[lennyo3034]

Essentially your eye is adjusting to try to focus on the reticle, which may be causing the image to lose focus momentarily until your eye tries to focus on the image before. It would get worse after using it for a bit and experiencing eye strain.

@koshkin could explain it better.

I've had this happen before and solved it by getting the diopter adjusted perfectly.

 

[cetanorak]

OK, that makes sense. I attempted to dial in the diopter on multiple occasions today, but I'll have to revisit my technique and check at the range again.

 

[hk dave]

Sounds like the diopter is not correctly set, or too much LSD.

 

[Bkultra]

Sounds like the diopter is not correctly set, or too much LSD.

No such thing as too much much LSD... Rebirth

 

[koshkin]

Essentially your eye is adjusting to try to focus on the reticle, which may be causing the image to lose focus momentarily until your eye tries to focus on the image before. It would get worse after using it for a bit and experiencing eye strain.

@koshkin could explain it better.

I've had this happen before and solved it by getting the diopter adjusted perfectly.

That's a good explanation.

 

[B-P-UU]

My guess is mirage as I experience this often as well while shooting with suppressor. Was the wind really low? That'll make it worse.

Even if the can is warm to the touch, that's a pretty large temp delta compared to 50 ambient.

 

[stello1001]

That happens to me a lot. It's your eye trying to focus. I know what you mean by assuming it's something psychedelic lol. It's like when you go to the eye doctor and they make you look through some machines and the little house in there on the orange background goes in and out of focus very quickly multiple times.

 

[Holliday]

My guess is mirage as I experience this often as well while shooting with suppressor. Was the wind really low? That'll make it worse.

Even if the can is warm to the touch, that's a pretty large temp delta compared to 50 ambient.

Had this issue the other day shooting out of a heated room. Mirage from the wood stove heat pouring out the window. Snow was coming down too. I actually started doing some sort of an averaging routine and was making great hits. Time consuming though.....

 

[Dthomas3523]

When I’ve had this happen, it’s either diopter or holding your breath too long (any is too long).

 

[KZP]

When I’ve had this happen, it’s either diopter or holding your breath too long (any is too long).

You mean having my limp body falling on the trigger from passing out is not good technique? I'm skeptical on this advice. Will try breathing next time I go to the range.

(I used to hold my breath, things would get fuzzy)

 

[pell1203]

Believe it or not, low blood sugar levels and dehydration, in conjunction with minor eye strain, can cause the exact symptoms you are describing.

It almost feels like your vision is behaving similar to an autofocus camera continuously making small corrections while trying to achieve the clearest image.

Issues more pronounced as your eyes get closer to their fifties and sixties and focus more sluggishly than when younger.

 

[Dthomas3523]

Believe it or not, low blood sugar levels and dehydration, in conjunction with minor eye strain, can cause the exact symptoms you are describing.

It almost feels like your vision is behaving similar to an autofocus camera continuously making small corrections while trying to achieve the clearest image.

Issues more pronounced as your eyes get closer to their fifties and sixties and focus more sluggishly than when younger.

I noticed much better results when I drink a small bottle of water per stage (or more in south Texas summers).

 

[cetanorak]

Believe it or not, low blood sugar levels and dehydration, in conjunction with minor eye strain, can cause the exact symptoms you are describing.

It almost feels like your vision is behaving similar to an autofocus camera continuously making small corrections while trying to achieve the clearest image.

Issues more pronounced as your eyes get closer to their fifties and sixties and focus more sluggishly than when younger.

Very interesting to hear, as I have never encountered this issue in the past. I wanted to believe that is was a technical issue with the hardware, however I couldn't help but wonder if, precisely as you have described, my eye was struggling to achieve focus. However, since the reticle remained sharp, throughout, that does again lead me to believe that there was perhaps some parallax or diopter adjustment issues (which could have triggered some sort of a vision-related enhancement of the out of focus effect).

 

[Vodoun daVinci]

In my opinion, having experienced the same thing some time ago, you are seeing mirage off of a hot barrel or suppressor. The fact that the reticle stays in focus tells me the target changing focus and drifting in and out is due to heated air rising off the barrel in front of the optic.

First time it happened to me I was certain it was eye fatigue as it went away when I waited a half an hour and then it returned after a few rounds.

The second time it happened I discovered that if I blew some air across the barrel it stopped only to return a few seconds later.

VooDoo

 

[morganlamprecht]

ive encountered a similar issue twice in the last month, both times under similar conditions and both times another shooter (not the same one both times) saw it also

both times we were shooting just before and after sunset on days when the sun was out all day and had everything heated pretty well, and then small cold fronts came in that evening

on one of the days we set up a light down range on a 500 and 800 yd target and we could see the same thing well after dark

it wasnt from barrel heat because both of us saw it even when we werent shooting for a while, barrels were cold with the temps in the low 50s, and low humidity...dry and crisp

we could sit there looking thru our scopes and the targets would get blurry for 2-3 seconds for both of us, then be back to crystal clear...was pretty strange

 

[DownhillFromHere]

Regarding eye focus changes with age... I've delved into this a fair amount over the years. Bottom line is that, by age 60, the lens of the eye is essentially crystalline and can no longer adjust focus. Hence, most of us end up needing bifocals or at least reading glasses by the time we're in our 50s.

I've had cataract surgery, so I have plastic lenses in my eyeballs that allow me to see 20/20 or even better on good days - but without readers I can't see fine detail closer than 6-8 feet.

The interesting thing re shooting is what this has meant for scope diopter adjustment. I use the standard technique of pointing scope at a blank wall and adjusting diopter in short time increments. My eye can't adjust that plastic lens, but it fatigues. So I get it adjusted, and afterward I know, short of catastrophe, my eye is not a variable in focus issues.

Interesting phenomenon with holographic sights (Eotech). The red dot/ring is crystal-clear in focus with no glasses. But if I put my readers on, that dot/ring is as blurry as a printed page would be without the glasses.

How does this apply to OP's question? Only another data point on diopter adjustment. It works better using a blank wall so the eye has nothing on which to focus except the reticle.

 

[918v]

It happens to me when it’s cold, like in the 40’s. I tested it this morning. It has nothing to do with the diopter and everything to do with barrel temp relative to ambient temp.

 

[cetanorak]

ive encountered a similar issue twice in the last month, both times under similar conditions and both times another shooter (not the same one both times) saw it also

both times we were shooting just before and after sunset on days when the sun was out all day and had everything heated pretty well, and then small cold fronts came in that evening

on one of the days we set up a light down range on a 500 and 800 yd target and we could see the same thing well after dark

it wasnt from barrel heat because both of us saw it even when we werent shooting for a while, barrels were cold with the temps in the low 50s, and low humidity...dry and crisp

we could sit there looking thru our scopes and the targets would get blurry for 2-3 seconds for both of us, then be back to crystal clear...was pretty strange

Sounds pretty damn similar to what I experienced. Strange, indeed.

 

[B-P-UU]

It happens to me when it’s cold, like in the 40’s. I tested it this morning. It has nothing to do with the diopter and everything to do with barrel temp relative to ambient temp.

I agree..

 

[Vodoun daVinci]

Range mirage is bad when the temperature is high....hot air rising off the ground is dreadful at high magnification and no wind. For me it's worse when the air temp is cool and the barrel gets warm...when air gets cool/dry and the barrel gets hot the air movement/distortion is very Freaky Deeky...the air current rising off a 140 degree barrel when the air temp is 40 Fahrenheit (or really dry) is very pronounced.

Cool/cold/dry air and a hot barrel is barrel mirage. When you experience undulating focus on the target and the reticle is crisp it is barrel mirage. Not usually a big deal at 10X unless the air is really cool. At 18X - 20X cool dry air and a hot barrel looks like a bad LSD trip thru a good scope.

VooDoo

 

[cetanorak]

Range mirage is bad when the temperature is high....hot air rising off the ground is dreadful at high magnification and no wind. For me it's worse when the air temp is cool and the barrel gets warm...when air gets cool/dry and the barrel gets hot the air movement/distortion is very Freaky Deeky...the air current rising off a 140 degree barrel when the air temp is 40 Fahrenheit (or really dry) is very pronounced.

Cool/cold/dry air and a hot barrel is barrel mirage. When you experience undulating focus on the target and the reticle is crisp it is barrel mirage. Not usually a big deal at 10X unless the air is really cool. At 18X - 20X cool dry air and a hot barrel looks like a bad LSD trip thru a good scope.

VooDoo

I’m feeling mostly certain that barrel/suppressor mirage HAS TO BE what was occurring, as this was my very first time shooting this setup in cooler temperatures, having just moved from TX to WA.

 

[Vodoun daVinci]

Cool air/hot barrel is a bugger for me at 18X. Looks good one minute and then when I simmer down and get tweaky shit starts to go in and out of focus while the reticle stays crisp and spanky.

Hot air rising off the barrel in cool air is weird shit for me.

VooDoo

 

[FourT6and2]

Any combination of some or all of the following:

1. Mirage
2. Diopter not adjusted properly, leading to eye strain
3. You're just tired, dehydrated, or need a snack

Most likely #2.

Your eye can focus on a blurry reticle to make it focused. But only for so long before it gets tired. For a reticle to be adjusted properly, it needs to be sharp when your looks at it, focused to infinity. I'm not talking about the parallax adjustment. I mean... hold your finger right in front of your nose. Look at it. Focus on it. It's hard to do! It hurts your eye muscles. Now look at a building way out on the horizon. It's easy. Takes no muscle strain at all. You want your reticle to be "at infinity" for your eye. That way you aren't looking at your reticle to focus it. You are looking at your target. And your reticle just happens to align with it and therefore it's focused without any effort. You should be able to get behind your rifle with both eyes looking at your target. Then get a cheek weld without changing your eye's focus. Boom... your target and reticle should both be in focus without your eyes needing to adjust.

If you get a sight picture and your reticle is blurry for a split second, and then your eyes adjust and now it's sharp... you've done it wrong. Your diopter is not adjusted properly. You should be able to stare at something off in the distance and then without changing your gaze, bring the scope in and your reticle is nice and sharp while you're still looking at that object on the horizon with both eyes.

That's how you know you can look through your scope for an hour straight without any eye fatigue.

 

[Last Chance]

Interesting...But, I've also experienced this...There was a 'some' mention of the effects age had on the eye's ability to adjust... I understand, if the diopter is properly adjusted, one's age shouldn't be a problem...( I spent a LOT of time and had difficulty trying to obtain a clear, crisp reticle using the 'blink' method.) My question is slightly different... I've adjusted my NF ATACR using the blank wall method...But, I've had cataract surgery...It feels to me like the lenses which were inserted in my eyes are moving/shifting which would account for this shifting focus using my rifle...Any thoughts???

 

[Brux]

When yall get this figured out let me know. I have experienced this lately myself.

 

[gopherslayer]

On one of my SWFA 3-9 I needed to extend the stock a bit and raise the comb to center my eye better. Mad e a world of difference. Magpul PRS are handy.

 

[Pipeliner134]

I've had that problem before at an indoor range. I'm not sure if it was lighting, ventilation or a warm barrel (not suppressed).

 

[cetanorak]

Just received a suppressor cover. Will adjust diopter accurately at home, mark the set point on the scope and then return to the range to see if issue persists.