Time lapse through the scope video? Am I imagining things

newguy2k3v2

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We've talked about how changing light, mirage, etc can affect poi. Frank has talked about dope changes at his Alaska classes on the podcast due to where the sun is in the sky.

I vaguely remember someone making a time lapse through the scope video looking at a target to illustrate how it appeared to move throughout the day but I can't find it. Anyone remember or have a link?
 

C.R. Adams

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I would be curious to know what the rifle is resting on in that video. I would have to question if the rubber feet of a bipod or leather of a front forearm rest was exposed to different heat during the day (expanding and contracting) or the sun heated the material differently on one side or the other as the sun moved through the sky.
 
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stevenc23

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I would be curious to know what the rifle is resting on in that video. I would have to question if the rubber feet of a bipod or leather of a front forearm rest was exposed to different heat during the day (expanding and contracting) or the sun heated the material differently on one side or the other as the sun moved through the sky.
He explains the setup in his description on the youtube link. Basically a spotting scope clamped down and enclosed in a box.
 
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CygnusX1

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IMHO, Looks like warm air turbulence making the target move/change size a bit.
The farther the target, the greater the effect

Like a light version of mirage
 

Skookum

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That range is facing west. The sun comes up behind and to the left and ends front to the left. At the end it starts to cast long shadows as it begins to dip behind those tall trees behind the targets,

When the shooter and the target are in the same thermal plane, the target is usually deflected away fron the source of light. This is seen in the video as the target image is reflected down in response to the rising sun.

However, what is interesting here is that the target image is deflected toward the source of light in the horizintal plane because there is a berm immediately right reflecting the light, and therefore the target image left.

The other illustrative point is to watch the crosshairs bounce up and down slightly as clouds pass over.
 
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Diver160651

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The other illustrative point is to watch the crosshairs bounce up and down slightly as clouds pass over.
Great post.. I do not know why people often think because the can shoot X size group at 100 yards, they'll get the same angular result way the hell out there.. Even without SD/ES and wind issues.. Optical is so underrated.
 
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morganlamprecht

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The other illustrative point is to watch the crosshairs bounce up and down slightly as clouds pass over.
i think i had something of this nature happen in a match a few months ago

sun was out, but mostly heavy clouds...the stage had 1moa x 2moa plates, 1 hung horizontal, and 1 vertical at each distance

distances were just over 500, 400, and 300....we had already shot the longer range stages out to 1100 yds and my dope was perfect, even on the thin coyote at 700ish

stage started far to near, 2 shots on every plate...i was clean until i got to the closest 300+ plates...i hit the vertical hung plate both shots, then on the horizontal i hit the T post just below...ignored that since i had already hit everything else all day, figured just a shank or funky round...sent the 2nd shot, smoked the t post again in the same spot...i thought i had dialed wrong or wrote the wrong dope, double checked, all good

buddy of mine who has been out shooting with me during some weird lighting shift issues we both noticed, mentioned the sun came out of the clouds for a brief moment during my last couple targets

this match allows 1 mulligan...the clouds came back, and i took my mulligan...cleaned all 12 shots holding level, elevation was spot on

similar could have been happening all day with the clouds, but most of the plates were 1.5moa+ and were big enough to eat up slight error

either something optically forced a shift, or i randomly shanked 2 shots just low perfectly into that t post
 

Diver160651

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or i randomly shanked 2 shots low perfectly into that t post
T-Post hit = Many shooters yelling EDGE HIT!....... as the bullet is redirected from the cheap pot metal as the thick, soft center spine of the T-post redirects it left or right.

Not directed in any way at you.. just reminded of another optical issue so common in our sport :)
 
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morganlamprecht

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lol yea, ive had shooters argue T post and hanger (if the target is angled a bit) hits quite a bit while RO'ing...mainly at 2 day matches

it was clear as anything, that was the first time that location had ran that stage in a match so the T posts were brand new painted green...put 2 nice gray 223 marks right under the plate lol
 
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Skookum

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i think i had something of this nature happen in a match a few months ago

sun was out, but mostly heavy clouds...the stage had 1moa x 2moa plates, 1 hung horizontal, and 1 vertical at each distance

distances were just over 500, 400, and 300....we had already shot the longer range stages out to 1100 yds and my dope was perfect, even on the thin coyote at 700ish

stage started far to near, 2 shots on every plate...i was clean until i got to the closest 300+ plates...i hit the vertical hung plate both shots, then on the horizontal i hit the T post just below...ignored that since i had already hit everything else all day, figured just a shank or funky round...sent the 2nd shot, smoked the t post again in the same spot...i thought i had dialed wrong or wrote the wrong dope, double checked, all good

buddy of mine who has been out shooting with me during some weird lighting shift issues we both noticed, mentioned the sun came out of the clouds for a brief moment during my last couple targets

this match allows 1 mulligan...the clouds came back, and i took my mulligan...cleaned all 12 shots holding level, elevation was spot on

similar could have been happening all day with the clouds, but most of the plates were 1.5moa+ and were big enough to eat up slight error

either something optically forced a shift, or i randomly shanked 2 shots just low perfectly into that t post
I spent a few hours doing this on purpose one day shooting paper at 200 yds. No lack of partly cloudy days in western WA state.

Result was 2 separate 10 round groups 0.3 mils apart on the vertical.

Was shooting over snow yesterday with my shooting partner. He had a Creed shooting 140's and I had my 308 shooting 175's. Both of us saw the exact same 0.2 mil upward shift in both our 100 yd zero's and at 504 yds. (Shot on paper and measured with calipers)

Both of us have many hundreds of rounds experience with these loads, and had shot this ammo out to 900 yds a few days prior.

Although not any kind of exact answer, I have seen a 0.3mil shift so often in these types of conditions that if I suspect a lighting condition needs accounting for then 0.3mils is always my first guess.
 

morganlamprecht

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I’ve seen similar on the random occasions I’ve encountered it

.2-.4 (most I’ve ever seen) so .3 would split that perfect
 

lowlight

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Snells Law

What happens is we flip small amount of warm air for cold air and vice versa

There was actually a British Documentary on the Bermuda Triangle, and during the show they spoke about Ghost Ships and how we often see ships that appear to be over the ocean and not on the water. They are hanging high in the sky. They demonstrated and explained how we are designed to see objects and the light waves in a very specific way. When you have situations were the warm air and cold air change positions it changes the amount of resistance the air gives the light waves changing our perception of the object.

So the object never moves but the air around it flips and moves the appearance of the object so we are not seeing its actual image but a reflected one.


There is a bunch of video on it, but it's super hard for us to figure it beyond, Believe the bullet, cause for us, it can happen long, or short, in a variety of ways.

We shoot west in Fort Morgan, and never see it, because we have next to no moisture in the air and our plains are not holding in cold air underneath the warm air
 

Namekagon

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So is there an "ideal" light condition to zero in? Or possibly better, a light condition that splits the difference in the movement (cutting 0.3 mil error into 1.5 mil error)?
 

lowlight

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It's pretty random and not just "light' there are other factors too

Light alone is not the issue, Moisture in the air, direction of fire, time of day, angle of the sun.

Certain ranges are more prone to the problem than other ranges. Like I said, on my private range, no issues at all, you can shoot any time and nothing changes but the wind. In Alaska at that range, we see it when the temps are shifting, the cold air sits low and heavy the sun comes up fast and the temps rise quickly, we see about 45 minutes of crazy stuff, then it's back to normal as the sun moves to change the angle to the target.

There are guys who insist on zeroing at certain times under certain conditions, but that is usually range dependent or the shooter being overly cautious.

When this effect bites someone it's usually short-lived.
 

Namekagon

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If I remember right it was mentioned on the podcast that, when this happens in Alaska, students suddenly start shooting high, correct? Are you seeing a similar 0.3mil of movement, or more?
 

lowlight

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I personally saw .5 Mil at 1000 yards with my 308 AX

I was hammering the target pretty hard, no wind in AK, and within a mag change my rifle started hitting .5 which most 308s saw, the 6.5s were between .3 and .5 too

It lasted a 1/2 hour when I saw it, then the sun moved and it went back to normal dope
 
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Skookum

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So is there an "ideal" light condition to zero in? Or possibly better, a light condition that splits the difference in the movement (cutting 0.3 mil error into 1.5 mil error)?
Some prefer to get a true "light neutral" zero by zeroing on a heavy overcast day. I live in the pacific northwest, so not hard to do here.

When I lived in Arizona, the only way to do it was to zero very early in the morning.

I wouldn't say that a light neutral zero is all important, even though it is my preference. I think the most important thing to know is simply that the effect exists.

If you know that it happens, then you won't be so quick to start tweaking velocities, bc's, etc...there might be another answer for what you are seeing.
 
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seansmd

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I remember it in our class in AK, and Frank and Marc saying it was going on. Not sure I had the confidence in my dope or my skills at the time to not blame me.
 
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Diver160651

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It's pretty random and not just "light' there are other factors too

Light alone is not the issue, Moisture in the air, direction of fire, time of day, angle of the Sun.
Good stuff, I'd like to add dust with super low sun angles. We used to go out in the dark to shoot ELR and wait for the Sun to rise, trying to beat the desert wind and mirage.

If it was super windy the night before, and still marginally windy as we began to shoot, the low angle quartering into the Sun combined with the dust, not only made the targets harder to resolve, but our dope seemed to be off from the clear mornings. At first, I thought it was our scopes getting lens flare, but even wrapping long paper over the objectives, the offsets would continue. Sometimes it just felt as we had shooter offsets, but it seemed to be roughly the same for everyone. The crazy part is, it appears that the more air distance you're looking through, the more noticeable it might be. I still remember going back to paper at 100, looking for an offset, and could not find it. I am not saying it is Snell's Law, maybe it is, but something funky can happen even when it is arid.

I'm not sure one would know it is present unless you happen to have the dope from the day before on the same target. As mirage comes up, that's another deal. I am not saying I have answers, just more questions. But I do laugh when someone gets the high horse and acts like they can hit an ELR MOA target all day long, with a small-caliber gun shooting .5-.75MOA at 100y; if they do their part.
 
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morganlamprecht

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Good stuff, I'd like to add dust with super low sun angles. We used to go out in the dark to shoot ELR and wait for the Sun to rise, trying to beat the desert wind and mirage.

If it was super windy the night before, and still marginally windy as we began to shoot, the low angle quartering into the Sun combined with the dust, not only made the targets harder to resolve, but our dope seemed to be off from the clear mornings. At first, I thought it was our scopes getting lens flare, but even wrapping long paper over the objectives, the offsets would continue. Sometimes it just felt as we had shooter offsets, but it seemed to be roughly the same for everyone. The crazy part is, it appears that the more air distance you're looking through, the more noticeable it might be. I still remember going back to paper at 100, looking for an offset, and could not find it. I am not saying it is Snell's Law, maybe it is, but something funky can happen even when it is arid.

I'm not sure one would know it is present unless you happen to have the dope from the day before on the same target. As mirage comes up, that's another deal. I am not saying I have answers, just more questions. But I do laugh when someone gets the high horse and acts like they can hit an ELR MOA target all day long, with a small-caliber gun shooting .5-.75MOA at 100y; if they do their part.
me and buddy saw the same once as far as distance affecting the offset

we were both .4 high @ 800, .2-.3 high @ 500, but spot on at 100

next time out to shoot, both our dope back to normal
 

stevenc23

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This helps explain it really well

 

lowlight

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lol that is not debunked it's a random forum with people disagreeing

look up shells law and watch the video they explain how the waves travel at different speeds hence the optical illusion we see

next time don't just post a lame ass link explain it if you think it's wrong

everything in your link is a guess
 

Luke

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Last year my wife and I were on a high speed ferry between Victoria & Seattle and there was a heavy inversion over the water - it caused a perfect upside-down image of the shoreline and ships on the water in the sky. Even when a distant ship dipped behind the horizon you could still see the upside-down reflected image in the air above it. I had always read about these types of atmospheric phenomenon giving away the location of fleets of enemy ships over the horizon back in the old sailing ship days, so it was neat to see it happen in person.
 

Hollywood 6mm

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Flori-duh.
This is something we see a lot on a couple of targets at Altus, especially in the winter time. .2-.3 high is the norm on C8 and C9, namely when the sun is low on the horizon and behind the targets.
 

lowlight

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As far as the bullshit debunked Post,

Fata Morgana mirages significantly distort the object or objects on which they are based, often such that the object is completely unrecognizable. A Fata Morgana may be seen on land or at sea, in polar regions, or in deserts. It may involve almost any kind of distant object, including boats, islands, and the coastline.

Often, a Fata Morgana changes rapidly. The mirage comprises several inverted (upside down) and erect (right side up) images that are stacked on top of one another. Fata Morgana mirages also show alternating compressed and stretched zones.[1]

The optical phenomenon occurs because rays of light are bent when they pass through air layers of different temperatures in a steep thermal inversion where an atmospheric ducthas formed.[1] (A thermal inversion is an atmospheric condition where warmer air exists in a well-defined layer above a layer of significantly cooler air. This temperature inversion is the opposite of what is normally the case; air is usually warmer close to the surface, and cooler higher up.)

In calm weather, a layer of significantly warmer air may rest over colder dense air, forming an atmospheric duct that acts like a refracting lens, producing a series of both inverted and erect images. A Fata Morgana requires a duct to be present; thermal inversion alone is not enough to produce this kind of mirage. While a thermal inversion often takes place without there being an atmospheric duct, an atmospheric duct cannot exist without there first being a thermal inversion.

The Optical and Air Inversion is then explained using Snell's Law,

This is the reason these things happen and why,

Snell's Law
Snell's law is used to determine the direction of light rays through refractive media with varying indices of refraction. The indices of refraction of the media, labeled
n_{1}
,
n_{2}
and so on, are used to represent the factor by which a light ray's speed decreases when traveling through a refractive medium, such as glass or water, as opposed to its velocity in a vacuum.

As light passes the border between media, depending upon the relative refractive indices of the two media, the light will either be refracted to a lesser angle, or a greater one. These angles are measured with respect to the normal line, represented perpendicular to the boundary. In the case of light traveling from air into water, light would be refracted towards the normal line, because the light is slowed down in water; light traveling from water to air would refract away from the normal line.

Refraction between two surfaces is also referred to as reversible because if all conditions were identical, the angles would be the same for light propagating in the opposite direction.

Snell's law is generally true only for isotropic or specular media (such as glass). In anisotropic media such as some crystals, birefringence may split the refracted ray into two rays, the ordinary or o-ray which follows Snell's law, and the other extraordinary or e-ray which may not be co-planar with the incident ray.


Fata Morgana is the short answer, why it happens is Snell's Law,

If you pay attention, they explain it is usually short-lived, which is what we see in shooting, it's caused by the layers of hot and cold air mixing which changes our perception of the image to do the change in medium. That change causes the light to change speed hence we see it wrong.
 
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stevenc23

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Was not implying that that Fata Morgana doesn't exist. BUT the video of that boat is Not Fata Morgana.
 
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Bigwheels

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My buddy & I saw the most refraction/displacement I've ever seen today.
Was shooting @ 1645yd across the valley in fresh snow with near calm wind & morning sun @ about 10 o'clock in relation to the azimuth.
We both had to dial .7-1.0 mil higher than normal today.
Started with the 1st and. Dialed 16.7 mil & hit almost 1 mil low. Stayed that way for the duration.
Can't account for the discrepancy otherwise.
Tgt was the black cliff face near the top across the valley.
20200308_115506.jpg
 

j-huskey

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This should be a STICKY...

This is very instructional to people who "think" they have a wandering zero.

Back in the day, when Townsend Whelen, Frank Brophy, and some of those ancients worked at government arsenals and in military development, they knew Snells Law and other sundry points that affected putting a bullet on target at longer ranges.

They had education levels long lost today. It is good to see this education and knowledge level being shown here in this topic,
the absence of education and knowledge creeps in as well, as some peoples lack of same is seen in a couple of responses.

How does this phenomenon affect shooters ?
What does it cost us ? Just how important is it ?

Several comments here appropriately note the effect is short lived, appearing in some specific light and atmospheric changes. Some have seen it in the early a.m., and I have seen it during all hours of the day in 45 years of shooting.

Once upon a time doing mil ranging exercises, using the fiberboard green smooth finish military popup target, we did an exercise to show light effect.
One side was smooth od green, the other side was almost a burlap sack weave dark tan.
You would get two different readings depending on the reflected light, with the instruction, read inside the edges on bright shiny highly reflective surfaces and read outside on light absorbing surfaces.

To further show these effects, we painted one each the smooth green side with gloss white paint, and gloss black paint.

Then we painted the absorbent side with flat white and flat black, one each.

That's 6 varying light absorbing/reflecting targets to range at this point.

Then, to further the effects, we painted one side each, in camo patterns, with both flat and gloss paints. That's now 8 targets to range.
Then, we altered the camo patterns to blend with the terrain background, that's 10 targets now.

We would put the targets out at 777 meters, on a straight across line from the firing line and with flat open ground behind them.

The light changing behind the targets also affected the readings.

Everybody got different readings on the 10 varied targets, some from appearance, some from the angle they were on the line. We moved everybody around on the line to get rid of the angular reading issues. But, the reflective nature of the targets gave varied readings, and when Snells law bumped in for those 15, 20, 30, 45 etc minutes, the readings were more varied.

We put mannequins dressed in fatigues and helmets out there as well. We used live range walkers. More different readings.

We had some fun and a LOT of frustration with those exercises. But, that exercise gives a really good example of the effects of both light refraction and light levels.

And what it costs in missed hits.


Further, with my police sniper team, the one I was lucky enough to have some members 10 years or more, and on 4 ranges, each with a different light direction,

The light changes consistently gave a half moa poi shift at 100 yards on the dot drill on targets based on reflective white paper.
Remember class, those ancient gun people created those targets for mil competition and training on light absorbent tan paper with a light absorbent flat black bullseye. That was in part to reduce the effects of Snells law and reflection and refraction.

*The current trend of shooting steel has compounded the error that Snells law and other "law/theory/etc" will create due to lighting conditions.*

What does it cause? Generally vertical poi changes.
And relative to results expected,
In mil use, this is/was not a problem on a vertical man. A torso hit was a torso hit.
In LE, a 100 yard half moa poi shift was not a problem in the 2x4" brain pan shot.
Most here arent going to be shooting past another human to hit a 2x2 area to stop the actions of another..... and perhaps this isnt germaine to this topic.

In competition, as targets shrunk more and more, its lower points and/ or a complete miss.

People who want to be champion competitors will look at many things that affect their performance and this topic is one that explains one of the often lost in white noise reasons for that otherwise unexplainable miss.

Excellent discussion.
vr
 
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Bigwheels

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If I had the the time & ammo it would have been very interesting to have reversed the shot firing back to the FFP to see if it remained the same, changed, etc. That was about double the vertical of the "norm".
 

Steel head

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I need to compare my notes from last week to this week as snow was melted yesterday
 

j-huskey

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If I had the the time & ammo it would have been very interesting to have reversed the shot firing back to the FFP to see if it remained the same, changed, etc. That was about double the vertical of the "norm".
I pulled my initial thought on your result from the post.
I'm still thinking abouts causes.

Fresh snow, = much drier air, can we quantify that ballistic change from a different trip.

Fresh snow, = much drier air, both more and less refractive potential for light.
a. Less moisture to reduce refraction,
b. Less moisture to reduce mirage,
c. Less moisture to create more brilliance from ground light reflections (more ambient brightness).

Just random thoughts. Like you, I would like to know the result of a reverse shot. Very curious.
 

Steel head

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I pulled my initial thought on your result from the post.
I'm still thinking abouts causes.

Fresh snow, = much drier air, can we quantify that ballistic change from a different trip.

Fresh snow, = much drier air, both more and less refractive potential for light.
a. Less moisture to reduce refraction,
b. Less moisture to reduce mirage,
c. Less moisture to create more brilliance from ground light reflections (more ambient brightness).

Just random thoughts. Like you, I would like to know the result of a reverse shot. Very curious.
Here when we have snow a 75-80% humidity or higher is common.
 

j-huskey

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45-80% on the west side.
East side can be considerably drier.
So, potential worst case, 30% humidity change, an ambient brightness change for visual with snow, and the added human misery factor.
Proven ballistic program can remove maybe 90% of the humidity error potential, and the rest, we may never know.

Sure is fun finding out, it's always positive when 350 grains hits that plate at a mile.
I am addicted.
vr
 

Steel head

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So, potential worst case, 30% humidity change, an ambient brightness change for visual with snow, and the added human misery factor.
Proven ballistic program can remove maybe 90% of the humidity error potential, and the rest, we may never know.

Sure is fun finding out, it's always positive when 350 grains hits that plate at a mile.
I am addicted.
vr
I really only notice changes in bright days with snow.
Most other changes are probably within my personal accuracy limitations.

I’m pretty good at writing notes for every target, every day and every rifle now with weather, wind and lightning conditions. Wea
It’s those bright snow days that can stand out.

Weather here is fairly mild compared to what I’ve seen.
 
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Bigwheels

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Conditions were as follows:
Temp 32*F
Press 28.06"
Hum 79%
Over the last 3 weeks I've been trying for a CCB shot on a 10" rock @ 1439 from the exact same FFP. Temps were within 2-3*. Humidity & press was also nearly the same. Always I was within .1 mil on that rock.
The wind there can be very difficult but all the fog floating around was going up not down so we can eliminate a strong down draft.
The snow & bright light is the only real difference aside from the range.
Also the range was provided by both our Terrapin x. Both gave the same readings +/- 1 yd.
 

Skookum

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Conditions were as follows:
Temp 32*F
Press 28.06"
Hum 79%
Over the last 3 weeks I've been trying for a CCB shot on a 10" rock @ 1439 from the exact same FFP. Temps were within 2-3*. Humidity & press was also nearly the same. Always I was within .1 mil on that rock.
The wind there can be very difficult but all the fog floating around was going up not down so we can eliminate a strong down draft.
The snow & bright light is the only real difference aside from the range.
Also the range was provided by both our Terrapin x. Both gave the same readings +/- 1 yd.
I don't know for sure, but my guess is that there was an inversion. The sun warming the air down in the valley and on the mountain sides, while the air in the middle remained cold, acting as a lens.

Just my guess.
 

Bigwheels

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Entirely possible. I don't pretend to know exactly what the cause was. I'm surmising that it was a refraction causing the change in poi. For all I know there could have been a 20 mph updraft but I highly doubt it. I would think the fog movement would have indicated that. We certainly saw or measured nothing like that. The prevailing breeze was 1.5-3 mph from about 150*. We could see fog drifting up the opposite slope but it was moving the same speed or slower.
Surprised both of us when we impacted so low. Don't remember ever seeing such a difference before.
 

j-huskey

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Curious about, same ammunition, ammo storage temps, and ammo temp each firing event.

We have 40° temp shifts here overnight during certain times of the year, and the duty rifle and ammunition has come out sweating. Sweats inside the brass as well to a degree and who knows what the eventual result is past 1000 yards. We never let a lot of duty ammo ride longer than 30 days.

In much hotter climates we some times (on the range/firing point) have it in covered "cooler bags" to keep the ammo temp down, never really thought about that in 32° temps.

Curious, very.