Battling Mirage - How Mirage Can Impact POI

[Rocketmandb]

It took a little while for me to publish this video due to a back issue I've been having, but I finally got it out.

This one takes a look at the basics of mirage, and how it can impact your POI. You guys who regularly shoot in the desert probably know this and will laugh at us uninitiated, but I usually shoot in the hills where we don't get mirage that impacts our POI... or do we?

 

[Bigwheels]

Good video. I have been trying to plot refraction for several years. It's hard enough when shooting across flat ground but there's no such thing in my AO. Never know which way it's going to go from one day to the next.
I've also seen the target follow the wind in mirage. Such as needing 0 wind when it's blowing 6mph. The wind dies & you're on the other side of the target.

 

[Holliday]

It took a little while for me to publish this video due to a back issue I've been having, but I finally got it out.

This one takes a look at the basics of mirage, and how it can impact your POI. You guys who regularly shoot in the desert probably know this and will laugh at us uninitiated, but I usually shoot in the hills where we don't get mirage that impacts our POI... or do we?

Look forward to watching this. I am sure to be dealing with mirage today at the range. Something to blame for my poor shooting…

Sorry about your back. I have a disk that apparently went missing after a climbing accident. Magnesium, daily, changed my life. (I happen to take D3 too which purportedly helps with absorption).

 

[Rocketmandb]

Good video. I have been trying to plot refraction for several years. It's hard enough when shooting across flat ground but there's no such thing in my AO. Never know which way it's going to go from one day to the next.
I've also seen the target follow the wind in mirage. Such as needing 0 wind when it's blowing 6mph. The wind dies & you're on the other side of the target.

Most of my shooting is in the hills and the target tends to be higher - they're almost always up on a hillside. From the earliest days of my ELR, my first shots at range were always on the order of .2-.4 mil low. I just ended up adjusting my dope and going from there. Now I think that in some cases and to some extent refraction is playing a role.

 

[Rocketmandb]

Sorry about your back. I have a disk that apparently went missing after a climbing accident. Magnesium, daily, changed my life. (I happen to take D3 too which purportedly helps with absorption).

Thanks - I take D3, but not Magnesium. Will look at that.

 

[EUBANKS]

Great video. Thanks for sharing.

 

[Holliday]

@Rocketmandb in watching this video, I find myself wondering if this refraction can happen to the laser in a rangefinder?

Last year while hunting Antelope with my buddy on the hot Wyoming high prairie, we were getting strange (dramatically short) ranges on our range finders. At the time I told my friend that I thought it was refraction, though I know next to nothing on the subject.

 

[Bigwheels]

I have wondered the same from time to time. Though a laser is simply focused light it must follow the same physics as any other light. But in this scenario the accuracy difference must me minimal. If the worst mirage I've ever shot in accounted for maybe 2 mils of trajectory. 2 mils @ even 2000 yds is only going to be feet off.
Since you could see the target the laser must be on the same path.
Unless your laser wasn't hitting the spot you were aiming at in the 1st place.
Have you box tested it to be sure where it actually hits in relation to the aiming reticle?

 

[Rocketmandb]

@Rocketmandb in watching this video, I find myself wondering if this refraction can happen to the laser in a rangefinder?

Last year while hunting Antelope with my buddy on the hot Wyoming high prairie, we were getting strange (dramatically short) ranges on our range finders. At the time I told my friend that I thought it was refraction, though I know next to nothing on the subject.

View attachment 8728126

Quick question: how short was dramatically short?

Until you get back to us (I'm interested to know - because I've experienced similar, but it was fog-related):

Most laser rangefinders we use for shooting operate at 905 nm wavelength, which is pretty long and in the infrared spectrum.

Wavelength will impact how much light refracts. Shorter wavelengths (toward the blue end) will refract more than longer wavelengths (red end). This is why we get prism effects.

Blue visible light is on the order of half of what LRF operate at. Yellow visible light is just above that at 570-590 nm. The refractive index is inversely proportional to the wavelength, meaning that if you halve the wavelength you double the refractive index and vice versa. See the image below of a prism and how the light bends more as you move more toward the blue end from the red end of the spectrum:

This means that if you were looking through an infrared scope at a target where refraction is impacting the view, the apparent location of the target would be closer to the actual than if you were looking through a straight up visual light optic.

As to whether that would impact the range reading... I need to noodle on that.

 

[CSTactical]

It took a little while for me to publish this video due to a back issue I've been having, but I finally got it out.

This one takes a look at the basics of mirage, and how it can impact your POI. You guys who regularly shoot in the desert probably know this and will laugh at us uninitiated, but I usually shoot in the hills where we don't get mirage that impacts our POI... or do we?

Excellent video, you should also post it in this section as well IMO

-Richard

 

[Rocketmandb]

Excellent video, you should also post it in this section as well IMO

-Richard

Thanks and will do.

Btw, recognize the scope? I was up at your shop a couple years ago to pick it up

 

[CSTactical]

Thanks and will do.

Btw, recognize the scope? I was up at your shop a couple years ago to pick it up

I'm glad it's part of your ELR journey -Richard

 

[Holliday]

Quick question: how short was dramatically short?

The antelope was 600+ yards and we were getting ranges in the 400 range with my Sig Kilo 2200 and his Leica binos.

It was extremely flat, clear ground. It was clear and sunny. It had been cold but the sun came out and heated upthe ground fast. Lot’s of mirage. The antelope was about 50 yards in front of a huge berm. If anything we should’ve been getting the berm behind it.

I had dropped down to scope the shot on my bipod and he was ranging. When he called out the range, I said there’s no way that’s 400 yards and I handed him my sig and he got the same range, so I took the shot. The bullet hit well in front of the animal, as one would expect.

I came up with the idea that the conditions were causing the laser to bend and hit the ground prematurely.

 

[Holliday]

Have you box tested it to be sure where it actually hits in relation to the aiming reticle?

Yes, my Sig is at about 1:30 on the small reticle circle ️. It has been very reliable.

Both his Leicas, have been considerably less reliable……

 

[Rocketmandb]

I came up with the idea that the conditions were causing the laser to bend and hit the ground prematurely.

Depending on the terrain, and what I experienced in the desert, I'd say possible... and maybe augmented by what I show in the video.

You'd be aiming with visible light that is bending more than the infrared laser. Depending on how the temperature gradient was going, it's quite possible the laser bent less and impacted the ground well in front of the animal.

EDIT: And quite possible that you were aiming at an apparent location that also caused you to go low.