Does anyone have a link to a web page that discusses or can advice on, how to evaluate and compensate for mirage, particularly when wind flag indications and mirage movement direction conflict? Thanks in advance.
Mirage
- Thread starter AI Perfector
- Start date
[br]STS said:
If that is true; What do you believe when mirage is moving in opposite directions at different ranges? [br]
To the OP: I suggest buying and reading Nancy Tompkins' book, "Prone and Long Range Rifle Shooting" and Linda Miller and Keith Cunningham's book, "The Wind Book for Rifle Shooters." Both books cover much more than mirage and approach the subject holistically.
BoydAllen
Gold $$ Contributor
Think as mirage as your last flag. Flags may disagree, because the wind is different at different distances from the shooter. The difference with mirage is that it also displaces the target's image. So it is a good idea to try to shoot all your shots when the mirage looks the same. Also, I suggest that you never shoot in a "boil", when the mirage is going straight up, unless you have aimed when the wind had blown the mirage away, and have confidence in your rest setup (shooting free recoil and holding point of aim). Doing it that way can work, but boil conditions are so rare, at least where I live, that counting on it is not a good plan.
When I aim at 200 yards, I can usually see the center ring of the target moving because of mirage, and because it is harder for me to precisely locate the center of a moving circle (and I am shooting for group and not score) some years back, I changed to a 6 o'clock hold, and I take that hold on the lowest position of that center ring (called the mothball) as is moves. I aim so that the outside of the line that defines the mothball, touches the top of the horizontal cross hair, and the vertical cross hair splits the mothball. By using this system, I think that I can aim more quickly and consistently. Other shooters may do this differently. I am just passing along how I do it.
One more thing, knowledge of mirage is best obtained by shooting scopes of 36X or higher. If you are using a lower power scope it would be more difficult to gauge, and although spotting scopes can be used to see it, without a reticle, they are a disadvantage for estimating the amount of movement, but of course you can see the flow and angle, if they are focused for that. I understand that highpower shooters may back off the focus of their spotting scopes to a shorter distance to better use mirage, but not so much that they cannot see the positions of the spotting discs that mark the location of their bullet holes on the target.
When I aim at 200 yards, I can usually see the center ring of the target moving because of mirage, and because it is harder for me to precisely locate the center of a moving circle (and I am shooting for group and not score) some years back, I changed to a 6 o'clock hold, and I take that hold on the lowest position of that center ring (called the mothball) as is moves. I aim so that the outside of the line that defines the mothball, touches the top of the horizontal cross hair, and the vertical cross hair splits the mothball. By using this system, I think that I can aim more quickly and consistently. Other shooters may do this differently. I am just passing along how I do it.
One more thing, knowledge of mirage is best obtained by shooting scopes of 36X or higher. If you are using a lower power scope it would be more difficult to gauge, and although spotting scopes can be used to see it, without a reticle, they are a disadvantage for estimating the amount of movement, but of course you can see the flow and angle, if they are focused for that. I understand that highpower shooters may back off the focus of their spotting scopes to a shorter distance to better use mirage, but not so much that they cannot see the positions of the spotting discs that mark the location of their bullet holes on the target.
On Camp Pendleton's Range 117, that would mean never shooting. 
Mirage moves the target, not physically but visually. My best estimate from 25yrs of prone group shooting is 1" per 60 yrds. A few years ago a friend and I would meet in the river bottoms to shoot a 1300 yrd setup we had. One year I called him and told him we needed to shoot right away because the crops had grown to the point where we could only see the top 2/3 of the target. We had to setup in the back of our trucks to see that much of it. As we shot all day on the target the sun would come out and raise the target well above the crops and the clouds would drop it back in them. At the sun's strongest point it would be 3ft above the crops and if we shot at what we saw then we shot that much high.
XTR
F-TR obssessed shooting junkie
Then there are days at Oak Ridge where the wind is coming in from 7:30 and swirling on the range so all the flags and the mirage are pointing left and the bullets are going right because they are flying above the tree line and in the "clean air'.
Yea, mirage never lies, I have coke at home, the Porsche is paid for ... you get the picture
Yea, mirage never lies, I have coke at home, the Porsche is paid for ... you get the picture
Don't you think it would be somewhat important to judge the impact of mirage at the level the bullets are traveling? Seems a bit odd to evaluate the effect of environmental factors that are in effect in a different place than your bullet. No offense, but I wouldn't judge the deflection on a bullet by wind significantly above or below the path of my bullet. Do you?
XTR
F-TR obssessed shooting junkie
You'd need to shoot here.
There is a creek across the range at 800 yards and about a 75" drop to the creek from the 1000 yard line, then the terrain slopes back up to the targets at 1000 yards at pretty much the same elevation as the shooting point. (we don't shoot up or down hill) The problem is that the flight of the bullets is over the treetops from about 800 to about 200 yards, but to try to look through that air and see mirage is looking at the tree tops 1200 yards away and on the hill above the targets, and I've tried but I can't make out mirage looking though the air at 65" above the ground with no horizontal features to see it against.
You don't even want to begin to talk about the vertical that it will induce if you have a tailwind or a headwind getting uplift off the berm at 800 and the hill to 900. This place sends a lot of people home thinking that they have a bad load.
There is a creek across the range at 800 yards and about a 75" drop to the creek from the 1000 yard line, then the terrain slopes back up to the targets at 1000 yards at pretty much the same elevation as the shooting point. (we don't shoot up or down hill) The problem is that the flight of the bullets is over the treetops from about 800 to about 200 yards, but to try to look through that air and see mirage is looking at the tree tops 1200 yards away and on the hill above the targets, and I've tried but I can't make out mirage looking though the air at 65" above the ground with no horizontal features to see it against.
You don't even want to begin to talk about the vertical that it will induce if you have a tailwind or a headwind getting uplift off the berm at 800 and the hill to 900. This place sends a lot of people home thinking that they have a bad load.
BoydAllen
Gold $$ Contributor
I believe that the closer your line of sight is to the ground, the more mirage you will have to deal with. I believe that what we call mirage are bubbles of less dense air bubbling up through slightly cooler air above it. and because the two densities have different refractive indexes, and the shape of the bubbles act somewhat like lenses, the image that we see is distorted. As the air rises, it mixes and past a certain point, these bubbles disappear. This is just a theory, what really needs to happen is that someone go out on a really heavy mirage day, take the bolt out of his rifle, and have someone raise a target a foot or two at a time from ground level to as high as can be managed, and take notes about how the mirage changes, and then reverse the direction of travel and make observations as the target is lowered. (Of course the rifle would have to be fitted with a scope that was 36X or higher.) Perhaps one of you that has a place where it won't scare anyone, and a fork lift, or zoom boom?
I assume you are not talking about 75 inches (") and mean 75 feet (') since you are shooting over the tops of trees. That would indeed be a difficult range to shoot. That being said, the mirage that you can't see well enough to evaluate still reacts to wind direction (or lack thereof) predictably. You gentlemen that shoot there have a lost one of the best range condition tools you have which is mirage.XTR said:
Boyd, you are exactly right in your observation of the severity of mirage the closer to the ground you get. As the ground is heated by the sun the air nearest the ground boils up in different densities and the further up you go the more difficult to see and figure out. If you really want some mirage go to the prairie country and shoot on a rolling piece of ground where your line of sight is a foot or less above the ground when it's 100 degrees. I move or have a Dr. Pepper.
Here's a question for you gents. If the suns energy is the major source of mirage does mirage occur at night and can it be read and evaluated?
XTR
F-TR obssessed shooting junkie
Yea, 75 feet.
I've never tried to shoot at night where there may be mirage. I imagine that in the early evening it may be visible over ground heated during the day. My range experience is that mirage vanishes when the the clouds come in.
Another thing about Oak Ridge, I've been told many times it is a mirage readers range. I described one condition where the wind and the mirage don't agree. There are a couple of windows here that the terrain will induce effects that aren't manifested in mirage, there are many other times where the mirage is responsive and in combination with the flags tells the story of where the bullet is going.
Back to the original question. There is a fair amount on the web and in books that will help. I've heard Nancy Tompkins book referred to with positive comments in more than one place. There is no substiture for getting out and shooting or scoring and watching what happens and trying to understand why. Every range has it's own personality caused by the terrain. Very few places are an open flat field with no effects from elevation or trees. Camp Perry has the wind tunnel over on the left. I didn't see it myself, but I was told that Raton is supposed induce some vertical on the left due to the elevation shift across the 100+ firing points. AEDC in Tullahoma has at least three distinct breaks in the tree line and berms at various ranges that can induce vertical or change the flight path of bullets. I've never fired at Camp Butner but I've been told they can have some unpredictable results.
Mirage is a tool, but it should not be the only tool you have to use.
I've never tried to shoot at night where there may be mirage. I imagine that in the early evening it may be visible over ground heated during the day. My range experience is that mirage vanishes when the the clouds come in.
Another thing about Oak Ridge, I've been told many times it is a mirage readers range. I described one condition where the wind and the mirage don't agree. There are a couple of windows here that the terrain will induce effects that aren't manifested in mirage, there are many other times where the mirage is responsive and in combination with the flags tells the story of where the bullet is going.
Back to the original question. There is a fair amount on the web and in books that will help. I've heard Nancy Tompkins book referred to with positive comments in more than one place. There is no substiture for getting out and shooting or scoring and watching what happens and trying to understand why. Every range has it's own personality caused by the terrain. Very few places are an open flat field with no effects from elevation or trees. Camp Perry has the wind tunnel over on the left. I didn't see it myself, but I was told that Raton is supposed induce some vertical on the left due to the elevation shift across the 100+ firing points. AEDC in Tullahoma has at least three distinct breaks in the tree line and berms at various ranges that can induce vertical or change the flight path of bullets. I've never fired at Camp Butner but I've been told they can have some unpredictable results.
Mirage is a tool, but it should not be the only tool you have to use.
I agree that mirage is a tool, and it certainly isn't the only tool at our disposal. But the original question was what to make of a conflict in conditions between mirage and flags. With regards to mirage at night, there most definitely can be mirage at night. Not only right after sundown but literally all night, especially if the day before was a very hot day. We used to shoot a NBRSA unlimited match at night in Kansas City once a year. On many occasions it would be DEAD CALM without so much as a twitch of a wind flag tail for hours on end, and slow running mirage would be clearly visable at 200 yards. I can assure you if you failed to detect a switch in the slow moving air mass that made that mirage move you would shoot a horizontal worm of a group even with a razor sharp rail gun. The mirage was sensitive enough to detect even the most subtle air movement and CORRECTLY show its direction. If you read the mirage right you could shoot some microscopic groups. When you see a left to right mirage you can be 100 % certain that there is a left to right wind somewhere on the range no matter if every flag on the range is pointing in the other direction. By the very nature of the different densities of air (mirage) any movement of that mirage will be 100% connected to air movement. We may not be able to see it well enough to use it, but it is there and doing its thing. It sound like the Oak Ridge range is one of those places that its difficult to read because of the drastic elevation change. That's a huge void to shoot over without good information and I can see why it would lead to some head scratching as far as load evaluation. I'd like to see the place sometime.
PRECISIONWELDING01
Gold $$ Contributor
Mirage and wind flags both lie my advice would be pay attention to both there is no right or wrong I assure you that .the best should get those 9's that are some what unexplained .your spotter my have seen what was going on but in position It seems you don't get as good of a read on it as you do while you are scoring
The unfortunate reality is that while both mirage or the range flags may lie... it's hard to know which one is telling you the truth unless you know the range... and you know the range under different conditions. Having said that, I'll put in another plug for Nancy Tomkins new book, Prone and Long Range Shooting; great stuff on reading the wind conditions and shooting strategy for dealing with the wind conditions.
STS said:
Sure. The mirage you see in your scope is localized to the point in space that it is focused(or un-focused) on. On a 1000 yard range during switchy conditions(flags in different areas pointing different directions at the same time), you can sometimes focus on the target, then back out and see the mirage change from one way to the other as you get farther out. For example, it might run left to right at 300 yards, but right to left at 700. Just like flags will do. So how do you know which one is right? If you hold center, when your bullet gets to the target it will either be on the right side or the left, not both, so you still have to figure out which is more important and what it's worth. Personally, I use mirage more than any other indicator when shooting, but there are times when I have found it is not the best indicator.
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