unshootable mirage

[DaveTooley]

I turn the power down some and slow down. Given a few more seconds your brain can average out the bumps and gyrations.

 

[dgeesaman]

Ok. Sightron scope. I don't know anything about those and since you didn't specify the exact model, I looked at the online specs for the SIIISS1050X60LR series. Since they didn't mention ED glass, I'm assuming the glass in those scopes is the regular kind.

My hypothesis, as described in my running thread, is that ED glass tames the mirage, reduces or eliminates the CAI. When I switched from regular glass to ED glass, the crazed amoeba covering the target got really placid.

The quality of the glass can not cancel the effect of the light being distorted as it reaches you from the target.

ED glass is a worthy upgrade for competition; I have no arguments there. But the mirage is occurring outside of the scope, and without some kind of wildly advanced digital solution, the best scope optics can only be expected to add to the the distortion as little as possible.

 

[Turbulent Turtle]

The quality of the glass can not cancel the effect of the light being distorted as it reaches you from the target.

ED glass is a worthy upgrade for competition; I have no arguments there. But the mirage is occurring outside of the scope, and without some kind of wildly advanced digital solution, the best scope optics can only be expected to add to the the distortion as little as possible.

I totally agree with that.

If you had read my other thread, you would have seen where I explain my hypothesis that non ED glass MAGNIFIES the effect of mirage and makes the image worse, whereas ED glass does not suffer anywhere near as much from the effect of mirage and present a better, more usable image. In other words, ED does not cure the distortion from the mirage, it doesn't make it worse like non-ED glass does.

 

[Turbulent Turtle]

As far as I know the SIII model differences are only in reticle design.

How does this relate to spotting scopes?
The other problem with mirage was that I never saw a bullet hole in paper all day.
Usually at 200 with a white target I can see them easily.

As I explained earlier, I know virtually nothing about Sightron scopes. At their website there are 3 different types of SIII scopes: The LR series, the Field Target series and the FFP series. Since you only gave the magnification range and not the full name, I had to infer a few things and that's why I picked the one I mentioned.

Spotting scopes will be affected by mirage also, but in competition, you want that. So, while my riflescope has Super-ED glass, my spotting scope has regular glass so as to show me the mirage in full force.

 

[dgeesaman]

I totally agree with that.

If you had read my other thread, you would have seen where I explain my hypothesis that non ED glass MAGNIFIES the effect of mirage and makes the image worse, whereas ED glass does not suffer anywhere near as much from the effect of mirage and present a better, more usable image.

I believe I read your other thread at some point but I did not make the correlation here.

In any case we agree.

David

 

[kzin]

As I explained earlier, I know virtually nothing about Sightron scopes. At their website there are 3 different types of SIII scopes: The LR series, the Field Target series and the FFP series. Since you only gave the magnification range and not the full name, I had to infer a few things and that's why I picked the one I mentioned.

Spotting scopes will be affected by mirage also, but in competition, you want that. So, while my riflescope has Super-ED glass, my spotting scope has regular glass so as to show me the mirage in full force.

Mine is LR fwiw at this point
I never knew or forgot the other two options exist, sorry.
Within LR there are multiple reticles which I assumed doesn't matter.

I'll go read your other thread at some point.
thanks for the input

 

[Turbulent Turtle]

I believe I read your other thread at some point but I did not make the correlation here.

In any case we agree.

David

Yes.

Being a simple man, I have to simplify things so that I can understand them. A method for doing that is to use an analogy. (Yes, I know, argument by analogy is a waste of time, but we're not arguing here. Analogies can be useful to explain things.)

I think of glass as the BC of the optics world. That works for coatings as well as glass type/quality. Keeping in the analogy, the objective size is the muzzle velocity. You let in more light (have a higher MV) with a bigger objective, but anything after that is going downhill. Once the mirage starts manifesting itself, the image gets progressively worse with the "low-BC" optics. The "high-BC" optics are also affected by the mirage, just not as much.

(Yeah, I know; it's lousy analogy but I think it gets the point across.)

 

[rjtfroggy]

I have a question, will a 4" sun shade help on a fixed power competition scope? (40 or 45 power) For 100-300 yard comps..

 

[Turbulent Turtle]

I have a question, will a 4" sun shade help on a fixed power competition scope? (40 or 45 power) For 100-300 yard comps..

I have a sunshade on most of my scopes for 2 reasons. 1- Protection for the objective lens. 2- Eliminate incident light for better IQ especially when aiming near the sun.

I remember a match at the 2016 Nationals in Lodi; late in the day, I was on the final relay and since the range is oriented east to west, the setting sun was in full bloom, so to speak. I was blinded. I crawled under a tarp that was also covering my spotting scope with its retractable sunshade extended all the way out. My riflescope also had its sunshade, which kept artifacts from showing up in the scope. The line of sight was very close to the sun; without a sunshade, it could have been pretty bad.

Another benefit is that I start my mirage shield just under the end of the sunshade.

ETA: A sunshade will do nothing for the mirage.

 

[WIB3]

Build a good tracking gun, trust your last sighter and let them fly. If your gun is tracking, no need to look thru the scope. Concentrate on shooting the gun and trust the professionals who made it. Don’t correct for the dancing patch for it will lie to you.

 

[Keith Glasscock]

Question:

How does a sunshade affect the reducing ring math from earlier in the thread? Does having the reducer farther from the objective change anything?

 

[WIB3]

There are times to trust your shooting ability and times to trust your smith. When the patch is dancing in your scope, shoot for group not got score.

 

[Turbulent Turtle]

Question:

How does a sunshade affect the reducing ring math from earlier in the thread? Does having the reducer farther from the objective change anything?

Excellent question. The answer is no, nothing changes. I have played with various color filters and the one time I tried the MD disk on mine, I placed it at the end of the sunshade. For the record, a medium yellow filter on my NF scope gave a little more contrast to view the mirage. Since switching from the NF NXS to a March, I've not taken the chance to try any filters. Maybe I need to do that, for data purposes. I have light yellow, medium yellow and I think a red somewhere.

 

[Scott Harris]

Shooting F class at Laurel MS one weekend and it was horrible. There was no way you could say you held the same spot twice. I came to the decision that if I ever had to shoot in mirage that bad again I was going to back off to 25 or less and dial.

It happened at Connaught last yr. I was shooting the Canadian Nats and the mirage was just abysmal. Dialed the whole match and held center. Shot the highest score I shot all weekend.

+1
I often go to about 15X in heavy mirage and use the reticle cross hairs to bracket the target and thereby center up. I always hold center.

 

[kvd]

Some March variable power scopes come with the aforementioned reducer but I've been lead to believe that with the power to reduce magnification, they really don't do much and are better used on fixed power scopes. Is that true?

There is a reason it is called mirage - because it is a mirage - an optical illusion. One more reason to not judge according to the seeing of the eyes. We know the truth that the target is stationary. For this reason, it is of vital importance to do everything possible to get the rifle to track perfectly and return to established POA every time. Having confidence that this is happening will then allow one to use the mirage to determine what the wind is doing down range. Perversely, when the boil is at its worst and straight up and down is the time to shoot because that is an indication of a calm in the wind. Don't let the mirage get the best of you and make it work for you.

My 2¢

 

[memilanuk]

Sounds like you're not looking at the dominant condition.

 

[Turbulent Turtle]

I have a thread running in the Optics section about mirage and glass. May I ask what scope you were using, make, model, etc?

Also, it's called "aperture", but what it really is, it's a way to cut down on the size of the objective lens in a way that will increase the depth of field and thus reduce the criticality of perfect focus that gets messed up by the mirage. If you make a hole in a cardboard sheet or a lens cap cover to be half the area of the objective lens, you will get the equivalent of 1 f-stop reduction. It will show more mirage because of the greater depth of field but it may reduce what I called the CAI, Crazed Amoeba Index; the pulsating center of the target viewed through a scope.

I did some quick calculations and if your objective lens is a 56mm, the diameter of the hole you need for 1 f-stop reduction is 39.6mm.

The formula is S = sqrt((O ^ 2) / 2)
Where S is the smaller objective diameter and O is the objective lens size (diameter) in millimeters.
If you want 2 f-stops reduction, change the 2 to a 4 in the division.

ETA: I corrected the definition in the formula above. Age is a terrible thing to have to deal with.

I am reposting the above to highlight the correction I made. The example calculation was correct and I used the proper term (diameter) in that line. However I mixed up diameter and radius in the explanation for the formula. I originally said, radius, but it's diameter. That's what happens when you drop the piece of Pi.

 

[Scott Harris]

My question is;
When the mirage is running towards 10:00 and I hold center x why are my rounds hitting a 4:00 7 ring

Are you saying it's the mirage causing a 4:00 7? Sure, mirage can reduce your X-count. But a 7 is the wind plain and simple. 4 0-clock...the wind doesn't only blow your bullet left and right....it can cause elevation 9s and even 8s? IMHO people over-estimate mirage error and greatly under-estimate what the wind is doing...especially with vertical. Shoot while the wind is changing direction and you can get some huge elevation shots. Shoot on a hot low-wind day in the desert and you will get elevation 9's on a regular basis.

 

[Turbulent Turtle]

Some March variable power scopes come with the aforementioned reducer but I've been lead to believe that with the power to reduce magnification, they really don't do much and are better used on fixed power scopes. Is that true?

That depends. Some people (like me) do not reduce magnification due to the phenomenon we incorrectly refer to as "mirage". (More on that below.) The MD disk supplied with some March scopes can be used at any magnification to expand the depth of field.

There is a reason it is called mirage - because it is a mirage - an optical illusion. One more reason to not judge according to the seeing of the eyes. We know the truth that the target is stationary. For this reason, it is of vital importance to do everything possible to get the rifle to track perfectly and return to established POA every time. Having confidence that this is happening will when allow one to use the mirage to determine what the wind is doing down range. Perversely, when the boil is at its worst and straight up and down is the time to shoot because that is an indication of a calm in the wind. Don't let the mirage get the best of you and make it work for you.

My 2¢

The term "mirage" is used incorrectly here, but since everybody calls it mirage, why fight it. The correct term would be "heat haze" or "heat shimmer," but for some reason we like our French terms in shooting: Mirage, Ogive.

A real mirage (the optical illusion kind) is when, for example, you're driving on a long straight road and in the distance, there appears to be water, even a lake, on the road ahead. That is a mirage and you do not need a riflescope to see it.

What we experience in our riflescopes is heat shimmer, which is a gradient in the refractive index of the air caused by the variation in temperature between the air at the ground and the cooler air above. This heat shimmer effect is enhanced by telescopic sights to where you can actually see it, which is why when you reduce the magnification the effect diminishes to where you do not even see it without an optics of some kind.

Also, it's a lot more fun saying "I'm watching the mirage" instead of "I'm watching the heat shimmer." It has more of a touch of erudition to it, don't you think?

 

[rardoin]

So Denys, what causes 'real' mirage? Is it not a change in the refractive index of the medium (air) through which the light (image) is passing caused by differential temperature of the layers? Edumucate me.