How do you practice

[xsn10s]

One other thing where I am above 42 degrees latitude where I shoot most often. May June and July shift further than October to February.

This is interesting to me because during March- July I am varmint hunting sagerats and hopefully chucks. So my shots are mostly 400 yards and less. Then fishing and if I'm lucky I'll be big game hunting. Most of my LR is early/ late in the year.

 

[Alex Wheeler]

Yes, need I again quote myself discussing mirage?

The center of an object that is stretched or compressed is still the center.

This phenomenon is not the same as Mirage. Mirage will typically make the target dance around and if there is wind it will carry the image in that direction. This is a very different thing that happens when lighting changes or the angle of lighting changes. I used to call this slow Mirage for lack of a better term because it happened when there was no Mirage present and it was a slow progression as things changed not fast the way in Mirage will move the image. It moves the target image similar to the way Mirage does. We have a similar issue that happens sometimes at matches. Our Target frames for the record Target get hung directly over top of the sighting Target. And in those 10 seconds it takes to hang the record Target certain days or certain relays everyone's group will shift up to a minute vertically. I have begun to believe that it is the angle of the record Target slightly different than the sighting Target which reflects the light at a different angle

 

[Matthappens]

This is a real phenomenon. Light refracts in air just as it does in water. It is just more subtle. I believe it is the angle of light, varying density of the air and due to how warm it is that causes this. The longer the shot the more affect it can have. It is kinda like mirage except the target is not bouncing, it is just not really exactly where you perceive it. This is actually a problem in surveying. They have formulas to account for it and take into account the time of day and I believe even temp when surveying. Complicated stuff...

Very interesting stuff, can you elaborate a bit more on the effects of this at long range and do you compensate for such a phenomenon? If so by how much?

 

[Barrelnut]

Very interesting stuff, can you elaborate a bit more on the effects of this at long range and do you compensate for such a phenomenon? If so by how much?

The long and short of it is that there is no current means to calculate and adjust for it in real time because air density is very variable and fluid. The biggest cause of refraction is changes in air density between you and the target AND even the angle of the light reflected from the target.

This is a know issue in surveying though and surveying incorporates a standard value to account for refraction when surveying long distances. The value is: 1/7 of the earths curvature error. The curvature error at 5 miles is about 14 ft.

I used the above numbers to calculate that the refraction error is about 2.75" at 1000 yards (as would be used in surveying). This is about 1/4 MOA. So, you could derive that light refraction in the atmosphere can account for an average of about 1/4 MOA Point of Impact error at any given time of day, temp, or pressure. It could also be way less or way more. But I would not be surprised at all to see a POI of 1/4 to 1/2 MOA at 1000 yards between morning and evening shoots. Then there is that cloud that rolls over right during you shot group and cools the air between you and the target....

I would also say that the possible 1/4 MOA change could also be present at 100 yards. Just depends on the air between you and the target. Litz actually discusses this phenomenon at about the 10 minute mark in the AB live question answer session they did a few days ago. He basically says there is no current method to accurately account for it in a ballistics solution. He also mentions that the error is usually more the closer to the ground the target is. I have read this is to be true due to the temp changes that can occur because of a cold pocket of air moving over a warm area of ground. It causes a warm to cold to warm air spot between you and the target. Makes sense right? Litz also says that the error almost doesn't exist in cross canyon shots where the air temp is more likely to be stable between shooter and target. Makes sense right?

Anyway here are a few links that discuss some of this stuff in varying degrees of detail. First one is a good Youtube video that explains the issue in surveying and how it is dealt with (refraction is discussed at about 2:18 in the vid.)
Second has the Litz comments at about 10 minutes in.
Rest are links to previous discussions on the forum.

Hope it helps.




https://www.longrangehunting.com/threads/light-and-its-effects-on-poi.36794/

https://www.longrangehunting.com/threads/how-does-sunlight-affect-your-poi.63167/

 

[WildRose]

The long and short of it is that there is no current means to calculate and adjust for it in real time because air density is very variable and fluid. The biggest cause of refraction is changes in air density between you and the target AND even the angle of the light reflected from the target.

This is a know issue in surveying though and surveying incorporates a standard value to account for refraction when surveying long distances. The value is: 1/7 of the earths curvature error. The curvature error at 5 miles is about 14 ft.

I used the above numbers to calculate that the refraction error is about 2.75" at 1000 yards (as would be used in surveying). This is about 1/4 MOA. So, you could derive that light refraction in the atmosphere can account for an average of about 1/4 MOA Point of Impact error at any given time of day, temp, or pressure. It could also be way less or way more. But I would not be surprised at all to see a POI of 1/4 to 1/2 MOA at 1000 yards between morning and evening shoots. Then there is that cloud that rolls over right during you shot group and cools the air between you and the target....

I would also say that the possible 1/4 MOA change could also be present at 100 yards. Just depends on the air between you and the target. Litz actually discusses this phenomenon at about the 10 minute mark in the AB live question answer session they did a few days ago. He basically says there is no current method to accurately account for it in a ballistics solution. He also mentions that the error is usually more the closer to the ground the target is. I have read this is to be true due to the temp changes that can occur because of a cold pocket of air moving over a warm area of ground. It causes a warm to cold to warm air spot between you and the target. Makes sense right? Litz also says that the error almost doesn't exist in cross canyon shots where the air temp is more likely to be stable between shooter and target. Makes sense right?

Anyway here are a few links that discuss some of this stuff in varying degrees of detail. First one is a good Youtube video that explains the issue in surveying and how it is dealt with (refraction is discussed at about 2:18 in the vid.)
Second has the Litz comments at about 10 minutes in.
Rest are links to previous discussions on the forum.

Hope it helps.




https://www.longrangehunting.com/threads/light-and-its-effects-on-poi.36794/

https://www.longrangehunting.com/threads/how-does-sunlight-affect-your-poi.63167/

THe biggest problems I see with refraction other than heat induced mirage is on dusty/smokey days or when there's a great deal of evaporation in an otherwise dry climate after a rain where air at the surface is carrying a great deal of moisture but much drier air just above it.

I've yet to find any method of accurately predicting any shift from it thus no shift in POA. Put it in the middle of the kill zone and let it fly.

Just like with Mirage the lower the magnification the less it affects you so just like in low light dial down till you have a good picture.

 

[Matthappens]

The long and short of it is that there is no current means to calculate and adjust for it in real time because air density is very variable and fluid. The biggest cause of refraction is changes in air density between you and the target AND even the angle of the light reflected from the target.

This is a know issue in surveying though and surveying incorporates a standard value to account for refraction when surveying long distances. The value is: 1/7 of the earths curvature error. The curvature error at 5 miles is about 14 ft.

I used the above numbers to calculate that the refraction error is about 2.75" at 1000 yards (as would be used in surveying). This is about 1/4 MOA. So, you could derive that light refraction in the atmosphere can account for an average of about 1/4 MOA Point of Impact error at any given time of day, temp, or pressure. It could also be way less or way more. But I would not be surprised at all to see a POI of 1/4 to 1/2 MOA at 1000 yards between morning and evening shoots. Then there is that cloud that rolls over right during you shot group and cools the air between you and the target....

I would also say that the possible 1/4 MOA change could also be present at 100 yards. Just depends on the air between you and the target. Litz actually discusses this phenomenon at about the 10 minute mark in the AB live question answer session they did a few days ago. He basically says there is no current method to accurately account for it in a ballistics solution. He also mentions that the error is usually more the closer to the ground the target is. I have read this is to be true due to the temp changes that can occur because of a cold pocket of air moving over a warm area of ground. It causes a warm to cold to warm air spot between you and the target. Makes sense right? Litz also says that the error almost doesn't exist in cross canyon shots where the air temp is more likely to be stable between shooter and target. Makes sense right?

Anyway here are a few links that discuss some of this stuff in varying degrees of detail. First one is a good Youtube video that explains the issue in surveying and how it is dealt with (refraction is discussed at about 2:18 in the vid.)
Second has the Litz comments at about 10 minutes in.
Rest are links to previous discussions on the forum.

Hope it helps.




https://www.longrangehunting.com/threads/light-and-its-effects-on-poi.36794/

https://www.longrangehunting.com/threads/how-does-sunlight-affect-your-poi.63167/

 

[Matthappens]

Wow that is amazing and it does make sense now that you explain it that way. This is why I love this sport, there is soo much to learn. Thank you for taking the time to give us more detail.
Regards,
Matt

 

[Matthappens]

The long and short of it is that there is no current means to calculate and adjust for it in real time because air density is very variable and fluid. The biggest cause of refraction is changes in air density between you and the target AND even the angle of the light reflected from the target.

This is a know issue in surveying though and surveying incorporates a standard value to account for refraction when surveying long distances. The value is: 1/7 of the earths curvature error. The curvature error at 5 miles is about 14 ft.

I used the above numbers to calculate that the refraction error is about 2.75" at 1000 yards (as would be used in surveying). This is about 1/4 MOA. So, you could derive that light refraction in the atmosphere can account for an average of about 1/4 MOA Point of Impact error at any given time of day, temp, or pressure. It could also be way less or way more. But I would not be surprised at all to see a POI of 1/4 to 1/2 MOA at 1000 yards between morning and evening shoots. Then there is that cloud that rolls over right during you shot group and cools the air between you and the target....

I would also say that the possible 1/4 MOA change could also be present at 100 yards. Just depends on the air between you and the target. Litz actually discusses this phenomenon at about the 10 minute mark in the AB live question answer session they did a few days ago. He basically says there is no current method to accurately account for it in a ballistics solution. He also mentions that the error is usually more the closer to the ground the target is. I have read this is to be true due to the temp changes that can occur because of a cold pocket of air moving over a warm area of ground. It causes a warm to cold to warm air spot between you and the target. Makes sense right? Litz also says that the error almost doesn't exist in cross canyon shots where the air temp is more likely to be stable between shooter and target. Makes sense right?

Anyway here are a few links that discuss some of this stuff in varying degrees of detail. First one is a good Youtube video that explains the issue in surveying and how it is dealt with (refraction is discussed at about 2:18 in the vid.)
Second has the Litz comments at about 10 minutes in.
Rest are links to previous discussions on the forum.

Hope it helps.




https://www.longrangehunting.com/threads/light-and-its-effects-on-poi.36794/

https://www.longrangehunting.com/threads/how-does-sunlight-affect-your-poi.63167/

 

[Matthappens]

So in your opinion what would the refraction be mainly at any distance, up and down or side to side? It seems to me like it would be a correction mainly up and down or is it random?

 

[Barrelnut]

So in your opinion what would the refraction be mainly at any distance, up and down or side to side? It seems to me like it would be a correction mainly up and down or is it random?

It is up and down only. Actually depends on how things were when you zeroed, I guess. Surveying vid says the bend is always down and from their perspective, I can see why. Litz says it is only up and down, but he was probably starting his observations from somewhere in the middle. They actually put a video camera on a scope positioned on a distant target and recorded the results through out the day.

 

[WildRose]

So in your opinion what would the refraction be mainly at any distance, up and down or side to side? It seems to me like it would be a correction mainly up and down or is it random?

Depeonds on the circumstances and what is causing it. Sometimes depending on the cause and light angle you will see a halo effect so you know it's there but you have no idea how to correct for it because it won't really give you a directional indicator or meausre of the effect.

Just like with mirage it can be moving up, down, sideways or at an angle. There really is no way to correct for it as it cannot be predicted with any accuracy.

You're totally in WAG mode. If anything a slight shift directly opposite what you are observing in the scope could be helpful but it's so variable I simply use the same POA as I would if it were totally indepectiable which it usually is other than in the case of mirage.

There is no real way to measure it except by comparing shots on a target so in the field you're on your own.

 

[WildRose]

It is up and down only. Actually depends on how things were when you zeroed, I guess. Surveying vid says the bend is always down and from their perspective, I can see why. Litz says it is only up and down, but he was probably starting his observations from somewhere in the middle. They actually put a video camera on a scope positioned on a distant target and recorded the results through out the day.

If you look at your own time sequenced video above you see it is both as it is shifting from lower left to upper right.

Sometimes you see things shortened, sometimes you see them narrowed or stretched outward depeonding on the angle of the light and what's causing the refraction. Hence often you'll see a halo or prism effect depending on the circumstances.

 

[TG-5150]

My wife and i have gotten into hunting rabbits with a 22lr. Ranges always vary along with shot angles and shooting positions.
Jackrabbits are pretty thick here in Wyoming.
I read through all this thread and have learned a few things . Thanks folks

 

[Pdvdh]

View attachment 109568 I get to the range and hang my steel at 600 yards. I get a rifle out of the truck, set up prone, dial, judge wind and shoot a cold bore at 600. I feel that's the best way to build skill in wind and cold bore. It's surprising how many hits I get with cold bore. Wind is my biggest worry when it comes to rifle shooting. One of my biggest accomplishments was getting over recoil anxiety, meaning not being afraid of the rifles recoil and just relaxing. There is fifteen 285 grain ELDs out of a Lapua in that hole. You can't anticipate recoil and shoot a Lapua like that.

600 yards? 15 shots all in one enlarged hole?