How to Read Mirage to Find Wind Direction and Strength

This was one of our 25 Most Popular Articles in 2017. We’re repeating it for those of you who may have missed it the first time around. Diagrams from SouthTexasShooting.org.

There is an excellent article about Mirage on the South Texas Marksmanship Training Center (STMTC) website. This article explains what causes mirage and how mirage can move the perceived aiming point on your target. Most importantly, the article explains, in considerable detail, how you can “read” mirage to discern wind speeds and wind directions.

Mirage Is Your Friend
While hot days with lots of mirage can be frustrating, mirage can reveal how the wind is flowing (and changing). If you learn how to recognize and read mirage patterns, you can use that information to shoot higher scores. That’s why many leading long-range shooters tell us: “Mirage is your friend.” As the STMTC article explains: “A mirage condition is not a handicap, since it offers a very accurate method of perceiving small wind changes[.]”

CLICK HERE to Read Complete Mirage Article

Mirage Illustrated with Diagrams
With simple but effective graphic illustrations, this is one of the best explanations of mirage (and mirage reading) we have found on the internet. This is a “must-read” for any serious competitive shooter. Here is a brief sample from the article, along with an illustration. NOTE: the full article is six times longer and has 8 diagrams.

The term “mirage” as used by the shooter does not refer to a true mirage, but to heat waves and the refraction of light as it is bent passing through air layers of different density. Light which passes obliquely from one wind medium to another it undergoes an abrupt change in direction, whenever its velocity in the second medium is different from the velocity in the first wind medium; the shooter will see a “mirage”.

The density of air, and therefore its refraction, varies with its temperature. A condition of cool air overlaying warm air next to the ground is the cause of heat waves or “mirage”. The warm air, having a lower index of refraction, is mixed with the cooler air above by convection, irregularly bending the light transmitting the target image to the shooter’s eye. Figure 1 shows (greatly exaggerated) the vertical displacement of the target image by heat waves.

Heat waves are easily seen with the unaided eye on a hot, bright day and can be seen with spotting scope on all but the coldest days. To observe heat waves, the scope should be focused on a point about midway to the target. This will cause the target to appear slightly out of focus, but since the high power rifle shooter generally does not try to spot bullet holes, the lack in target clarity is more than compensated by clarity of the heat waves.