Mirage; Reading and Compensation

[Laguna Freak]

Today my "work" conditions were such that I was able to run out to the range about 10:30 am to do a little seating depth work at 300 yards. I knew it was forecast to be about 74F and clear but I didn't even consider the mirage potential when I was loading the truck. By the time I sat down at the bench I could detect a faint mirage through the clear lens of my safety glasses. When I looked through the scope, I thought "****, that's disappointing" as my PoA was dancing around in the shape of a daisy head outline while mirage appeared steady from 3:00 to 9:00. At that time the wind was barely perceptible from right to left at the bench and the target is back in the trees. I made sure AO parallax was set, then I adjusted my eyepiece back and forth a bit trying to clear the picture. The PoA daisy head dance remained relentless but was a bit clearer. After about 15 minutes of studying up on reading mirage, because I suck at it, I decided I'd try one round of known performance and go see. At the time, the wind had switched from 2:00 to 11:00 at the bench and was even lighter. The mirage appeared to now be moving from 9:00 to 3:00 at the target. I figured there must be more vertical than I was discerning. So I held about 1" low and 1" left. I felt like my breathing control, steady aim, and trigger squeeze were perfect and I was mildly surprised by the discharge. Well, PoI was 3" low and 4" left. It was pointless to shoot more because I wasn't there to practice mirage reading and compensation. So this evening I found these weblinks that offer some insights. Maybe some of y'all will find them helpful.

Reading Mirage

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South Texas Marksmanship Training Center - Reading Mirage

 

[Huntnful]

I'm pretty sure load development and checking ballistics in actual, hazy mirage is pointless. "Reading mirage" is for the wind and when you have to TRY and see it. Not when it's completely distorting the entire target. When the actual air is distorted when you can see it with your naked eye, your data is going to be trash basically lol. Unless you're just getting velocities. I live in a humid area at sea level. I go shoot before the sun even comes up for that reason. My impacts can shift as much at 6" at 600 yards just from the mirage if I decide to shoot in it.

 

[Bravo 4]

I was trying to do some load testing at 1500 yards recently, the mirage caused the 15" plate to completely bounce around the reticle from one side of the target to the other. Complete waist of time, went back early the next day and had really good conditions.
We had been also doing a range estimation exercise on a flight line, for appearance of objects (naked eye) and using the scope reticle (mil-relation formula). You want to talk about a crappy outcome but real world conditions , like the guy was dancing in front of you. Looked like the Mad Hatter doing the Futterwacken.

 

[Laguna Freak]

I'm pretty sure load development and checking ballistics in actual, hazy mirage is pointless. "Reading mirage" is for the wind and when you have to TRY and see it. Not when it's completely distorting the entire target. When the actual air is distorted when you can see it with your naked eye, your data is going to be trash basically lol. Unless you're just getting velocities. I live in a humid area at sea level. I go shoot before the sun even comes up for that reason. My impacts can shift as much at 6" at 600 yards just from the mirage if I decide to shoot in it.

Yep. That's why I fired 1 and left after seeing PoI

 

[Huntnful]

Yep. That's why I fired 1 and left after seeing PoI

Yep, that's what I would have done also haha

 

[Beluebow]

I was trying to do some load testing at 1500 yards recently, the mirage caused the 15" plate to completely bounce around the reticle from one side of the target to the other.

We call this mirage image shift. You can learn to measure this with the right reticle and make educated allowances for your shots should the situation arise. It does take some time and practice.

Being a big proponent of ladder tests, I refuse to test in heavy mirage. I'll just pack up and go home instead of wasting components.

 

[david g ranes]

That's why people run initial tests at a hundred yards to do away with a lot of environmental issues then fine tune later. David

 

[Laguna Freak]

I went out to play at 300 yd in the wind again today. Lucky me, the Weather Liar was wrong again and I got moderate mirage too. Welcome to S TX.

Wind was 15 to 20 and generally from about 1:00 with occasional shift to 11:00 and one brief lull period with cloud cover that killed the mirage entirely and allowed PoI to align with PoA. I chose PoA on a prevailing conditions wild guess and stuck with it to learn how wind driven mirage moves the target image as viewed through the scope. On the target, the top right impact is the brief lull with cloud cover = no mirage. The 4 bottom left impacts are the prevailing wind + mirage. The bottom right impact is a wind switch to ~ 11:30 + mirage. This target provides visual representation of why I now choose to practice with known performance loads in such conditions. As the Benchrest shooters know, if you don't learn the effect of wind driven mirage when the cost is low, you darn sure won't know it when it matters most and the cost has become exponentially higher.

 

[Jon Bischof]

I hate mirage. Now I am going to have to learn to read it.

 

[waveslayer]

load testing can be performed at 100 to reduce mirage.

I would hang the targets higher off the ground myself. Just get some tall 2x2's and keep them in the truck if your in Texas.

Mirage is easy to read, any wind over 12mph is going to flatten the mirage and then it's pointless to use for any wind indicator, you need to look at the grass and trees. takes about 15mph to move most big trees. best is to get a Kestrel and practice all the time around the house etc.

PM and I can email you a good Mirage reading tool I have had from a long time ago. Think some undisclosed guy from Cornado gave it to me. He was an okay sniper

 

[Jon Bischof]

Don't necessarily need to use mirage to measure wind, but do want to be able to adjust my poa to compensate for mirage image shift.

 

[david g ranes]

Don't necessarily need to use mirage to measure wind, but do want to be able to adjust my poa to compensate for mirage image shift.

get on YouTube look up winning in the wind he has the best info on shooting in mirage I've seen anyone explain. David

 

[BallisticsGuy]

Reduce magnification and if that don't work, don't bother shooting. Mirage can be read as an indicator but it is a far from perfect way to determine the exact correction needed.