Mirage is one of those things that can render even the most expensive and best spotting scope useless. However, a quality spotting scope can still help you hit your target dead-on. Clarity is what you want and quality scopes have the glass to give it.
But, how can you compensate for mirage when it's killing your aim? If you're into long range shooting like competitive bench-rest, or if you're just trying to wrap your head around the mirage phenomenon, squint no further.
We've put together a tip guide to help you make the most of mirage - reading wind speed. First, let's get the foundation squared away.
What is Mirage?
Without getting all technical with cold and warm air, refracting light, and the gradient index of air, let's just lay it out. Mirage is that wavering, moving wall of air that distorts your image and makes it look like it's jumping, shifting, and moving out of place constantly. It can be the bane of your hunt or competitive shoot since you can't quite get your crosshairs dead-on. But, if you can use mirage to read wind speed and direction, it can be a boon to help you make your adjustments as accurate as they can be.
Why is Wind Relevant?
Mirage is going to be apparent regardless if there's a slow wind, rapid wind, or no wind at all. The pattern in which mirage is moving will tell you if wind will be an issue in accuracy and if you need to compensate, wait for wind to shift, or to simply call it a day.
As many competitive shooters, long range hunters, and professional snipers will know, wind absolutely has an effect on your intended bullet impact. It has the potential to cause your shot to completely come off the mark or miss it entirely, and it will present consequences, especially if the first shot counts. Let's get into how you can up your chances for a clean, accurate shot when you've got mirage as an unwelcome companion on your range.
8 Tips to Using Mirage to Read Wind Speed
1. Use a Spotting Scope
Rifle scopes are much lower-powered than a spotting scope. Spotters typically pick in magnification where rifle scopes and binoculars leave off. This gives them the advantage of being able to see closer details much further away. But, when it comes to mirage, a spotting scope has the ability to observe what mirage is doing at the target. You don't want to overshoot your focus beyond the target when mirage is present. Doing so can significantly alter your image, perception, and correct distance. A good rule of thumb is to focus in to the target and then dial back down to somewhere between half way and 3/4 of the way to the target.
Additionally, to maximize your success in reading true wind direction with a spotting scope, you want an optic that can rotate and move an image. Simply put, a spotting scope can do this and a rifle scope can't.
2. Ditch the Anemometer
If it was so easy to read wind velocity and how it will affect your shot, we'd all be carrying anemometers 24/7. However, there's a reason most of us aren't. Anemometers only read wind velocity in one location - where you're standing. The problem with this is, wind speed can be different at your target point and in the middle ground than where you'll be shooting from. This one reading presents many limitations. Instead, do some heavy lifting and learn to read mirage.
3. Reduce Magnification
Yes, the best thing about spotting scopes is that they're high-powered. However, this can present an obvious issue, clarity is reduced. As your image is magnified, you compromise your clarity. This is even more so when mirage is present. The scope power needed to read mirage is at about 25X to keep your image close enough, intact, and clear. As a side tip, if you're using a high-powered rifle scope, bring down the power to about 10-12X instead of 16X to reduce the effects of mirage. This is where premium glass in high-quality spotting scopes outshine the budget ones. The best spotting scope for reading mirage is always going to be the one with the best glass.
4. Determine Mirage Density
The heavier the mirage is, the more increases in sight corrections you'll need to make. Mirage is classified into three distinctions: light, intermediate, and heavy. Here's what it can look like.
- Light - Target and image distortion is low. It may be a cool or cloudy day where the ground isn't hot enough to interact with cool air above it. Through a spotting scope, you may only see faint lines. This can be ideal mirage conditions to detect wind velocity.
- Intermediate - Target and image distortion is moderate. You may be able to see it with the naked eye, but it's obvious through a spotting scope as distinct lines. The weather may be perfect temperature in the 70 degrees with normal humidity around 50 percent. Conditions are workable to detect wind velocity to make necessary adjustments.
- Heavy - Target and image distortion is significant. Mirage can be seen with the naked eye and are extremely apparent as distinct, constantly moving lines through a spotting scope. The weather may be very hot, and humidity will be high. Reading wind velocity and shifts in heavy mirage will take much practice to determine accurate corrections for adjustments.
5. Determine Wind Direction: Part 1
The way in which mirage is moving will tell you a lot about wind speed and direction. Simply look at a flag on the range, a plastic bag caught on a tree limb, the moving canopy of the trees, or the swaying grass blades. Yes, any one of these things, especially a flag on the range can tell you wind direction, but when you're out in the field, you mightn't have anything but leafless vegetation around like in the plains of the Southwest.
While you should depend on the topography around you to aid in estimating wind effects, you can also count on mirage. But, while you might know the direction, say it's coming from the East, or it's blowing from left-to-right, it's not the only factor that will be involved in your shot. You've got to know about the four distinct classes of mirage that can help you further determine where the actual target is in relation to its image.
6. Determine Mirage Classification
Knowing the type of mirage you're dealing with can tell you how far off the image is from the target. You might know that at this moment you have a running left-to-right wind and mirage is at a 30 degree angle, so you may not be as far off as you thought. If you can determine your mirage class, you can also determine where your target is and how you much you need to holdover. Here's how to read mirage for wind speed and what to do about it.
- Boiling Mirage: This is a vertical mirage where there is no wind present. Mirage is rising in an upward motion and appears to be jumping or floating upwards. Depending on your type of shooting and the density of the mirage, you'll need to lower your sights to get dead-on.
- Slow Mirage: Heat waves will move in motion from points of 7 o'clock to 1 o'clock or 5 o'clock to 11 o'clock. Because of the apparent incline in mirage, the 30 degree angle indicates a wind speed of 1-3 mph. You will need to make both elevation and windage adjustments for a lower point of aim and for bullet drift.
- Medium Mirage: Heat waves will move in motion from points of 8 o'clock to 2 o'clock or 4 o'clock to 10 o'clock. Because of the increased incline in mirage, the 60 degree angle indicates a wind speed of 4-7 mph. You will again need to make both elevation and windage adjustments for a lower point of aim and for bullet drift.
- Fast Mirage: Heat waves will move in motion from points of 9 o'clock to 3 o'clock and vice versa. There is no incline in mirage as a wind speed of 8-12 mph pushes heat waves in a horizontal motion across the face of the target creating the distorted image at a 90 degree angle. There is no need for an elevation adjustment, only the need for windage correction for wind drift.
- Boiling Lateral Mirage: This is an extreme case of mirage where you've got boiling heat waves with lateral left or right secondary heat waves. They're very difficult to distinguish because you're now dealing with two wind components at various angles. However, the secondary heat waves are the fainter than the primary ones and they're the ones you want to pay attention to to determine wind shifts. Both elevation and windage adjustments need to be made.
You should note that mirage can't be seen once wind velocity is past 12 mph.
7. Determine Wind Direction: Part 2
Now that we've covered wind speed, angles, and mirage classifications, let me help you further determine true wind direction. If you're not wanting to guess angles based on your poor measuring skills, leave it to your spotting scope.
As we've established, a "boil" means there's no wind. However, there's a silver lining here. If you can get your scope axis on the same plane as wind direction, you'll also see a boil. This means that your scope is inline with wind direction. Here's how you do it.
- Ensure you have a good background of mirage.
- Rotate the spotting scope mount until you see boil.
- Ensure heat waves are moving in the boil pattern (rising up).
- Note the scope body angle on the spotter.
With this method, your scope can give you the angle of the mirage which tells you the wind direction and how far off your image is from the actual target. This is also a good way to determine when wind shifts are going to happen since boils always precede shifts.
8. Record Everything
To really be a champion, you've gotta be able to look downrange and know how the factors from where you are to your target will make a whole lotta difference on paper. If you're just trying to hold around 2 MOA, then you mightn't need any of this. But, if you're trying to be surgically precise and better than 1/2 MOA, you're going to need to do your homework on mirage.
The key is to keep a record of your target distances, time of day, rifle and ammo used, weather conditions, scores, and everything about mirage. You could also get in with a long range team and sit in on the match sessions. You can listen to the coach call out corrections to the shooter and compare scores afterwards. When it's a multiple shooter contest, line your spotting scope to see multiple targets at once and see how mirage is different at various distances and how it affected their bullet. You might even be able to see where a shooter failed to miss a shift. With observation, practice, and popping off rounds, you'll soon be able to read mirage like an old friend.
Reading Mirage Is as Complicated as You Make it!
There's quite some math and fancy science definitions to how mirage affects shooting. But, you can always cut yourself some schooling by shooting when mirage would be less of a problem like at sunrise or when it's pretty overcast outside.
But, if you're not the type to let a little mirage get in the way of your trigger-happy attitude, then get out there and observe what the wind is doing. It only gets as complicated as you make it. Practice and record-keeping can make you a precision shooter, even when mirage insists on hanging out!
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Simon is an avid outdoor enthusiast and the owner of Target Tamers. He is passionate about bringing you the most up to date, accurate & understandable information on sports optics of all kinds and for all applications. When not glassing the local wildlife, you can find him in the garden with his German Shepherd.